//! Conversion from AST representation of types to the `ty.rs` representation. //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an //! instance of `AstConv`. mod bounds; mod errors; pub mod generics; mod lint; mod object_safety; use crate::astconv::errors::prohibit_assoc_ty_binding; use crate::astconv::generics::{check_generic_arg_count, create_substs_for_generic_args}; use crate::bounds::Bounds; use crate::collect::HirPlaceholderCollector; use crate::errors::{AmbiguousLifetimeBound, TypeofReservedKeywordUsed}; use crate::middle::resolve_bound_vars as rbv; use crate::require_c_abi_if_c_variadic; use rustc_ast::TraitObjectSyntax; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::{ struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, FatalError, MultiSpan, }; use rustc_hir as hir; use rustc_hir::def::{CtorOf, DefKind, Namespace, Res}; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::{walk_generics, Visitor as _}; use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin}; use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt}; use rustc_infer::traits::ObligationCause; use rustc_middle::middle::stability::AllowUnstable; use rustc_middle::ty::subst::{self, GenericArgKind, InternalSubsts, SubstsRef}; use rustc_middle::ty::GenericParamDefKind; use rustc_middle::ty::{self, Const, IsSuggestable, Ty, TyCtxt, TypeVisitableExt}; use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS; use rustc_span::edit_distance::find_best_match_for_name; use rustc_span::symbol::{kw, Ident, Symbol}; use rustc_span::{sym, Span, DUMMY_SP}; use rustc_target::spec::abi; use rustc_trait_selection::traits::wf::object_region_bounds; use rustc_trait_selection::traits::{self, NormalizeExt, ObligationCtxt}; use rustc_type_ir::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable}; use std::fmt::Display; use std::slice; #[derive(Debug)] pub struct PathSeg(pub DefId, pub usize); #[derive(Copy, Clone, Debug)] pub struct OnlySelfBounds(pub bool); #[derive(Copy, Clone, Debug)] pub enum PredicateFilter { /// All predicates may be implied by the trait. All, /// Only traits that reference `Self: ..` are implied by the trait. SelfOnly, /// Only traits that reference `Self: ..` and define an associated type /// with the given ident are implied by the trait. SelfThatDefines(Ident), /// Only traits that reference `Self: ..` and their associated type bounds. /// For example, given `Self: Tr`, this would expand to `Self: Tr` /// and `::A: B`. SelfAndAssociatedTypeBounds, } pub trait AstConv<'tcx> { fn tcx(&self) -> TyCtxt<'tcx>; fn item_def_id(&self) -> DefId; /// Returns predicates in scope of the form `X: Foo`, where `X` /// is a type parameter `X` with the given id `def_id` and T /// matches `assoc_name`. This is a subset of the full set of /// predicates. /// /// This is used for one specific purpose: resolving "short-hand" /// associated type references like `T::Item`. In principle, we /// would do that by first getting the full set of predicates in /// scope and then filtering down to find those that apply to `T`, /// but this can lead to cycle errors. The problem is that we have /// to do this resolution *in order to create the predicates in /// the first place*. Hence, we have this "special pass". fn get_type_parameter_bounds( &self, span: Span, def_id: LocalDefId, assoc_name: Ident, ) -> ty::GenericPredicates<'tcx>; /// Returns the lifetime to use when a lifetime is omitted (and not elided). fn re_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Option>; /// Returns the type to use when a type is omitted. fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>; /// Returns `true` if `_` is allowed in type signatures in the current context. fn allow_ty_infer(&self) -> bool; /// Returns the const to use when a const is omitted. fn ct_infer( &self, ty: Ty<'tcx>, param: Option<&ty::GenericParamDef>, span: Span, ) -> Const<'tcx>; /// Projecting an associated type from a (potentially) /// higher-ranked trait reference is more complicated, because of /// the possibility of late-bound regions appearing in the /// associated type binding. This is not legal in function /// signatures for that reason. In a function body, we can always /// handle it because we can use inference variables to remove the /// late-bound regions. fn projected_ty_from_poly_trait_ref( &self, span: Span, item_def_id: DefId, item_segment: &hir::PathSegment<'_>, poly_trait_ref: ty::PolyTraitRef<'tcx>, ) -> Ty<'tcx>; /// Returns `AdtDef` if `ty` is an ADT. /// Note that `ty` might be a projection type that needs normalization. /// This used to get the enum variants in scope of the type. /// For example, `Self::A` could refer to an associated type /// or to an enum variant depending on the result of this function. fn probe_adt(&self, span: Span, ty: Ty<'tcx>) -> Option>; /// Invoked when we encounter an error from some prior pass /// (e.g., resolve) that is translated into a ty-error. This is /// used to help suppress derived errors typeck might otherwise /// report. fn set_tainted_by_errors(&self, e: ErrorGuaranteed); fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span); fn astconv(&self) -> &dyn AstConv<'tcx> where Self: Sized, { self } fn infcx(&self) -> Option<&InferCtxt<'tcx>>; } #[derive(Debug)] struct ConvertedBinding<'a, 'tcx> { hir_id: hir::HirId, item_name: Ident, kind: ConvertedBindingKind<'a, 'tcx>, gen_args: &'a GenericArgs<'a>, span: Span, } #[derive(Debug)] enum ConvertedBindingKind<'a, 'tcx> { Equality(ty::Term<'tcx>), Constraint(&'a [hir::GenericBound<'a>]), } /// New-typed boolean indicating whether explicit late-bound lifetimes /// are present in a set of generic arguments. /// /// For example if we have some method `fn f<'a>(&'a self)` implemented /// for some type `T`, although `f` is generic in the lifetime `'a`, `'a` /// is late-bound so should not be provided explicitly. Thus, if `f` is /// instantiated with some generic arguments providing `'a` explicitly, /// we taint those arguments with `ExplicitLateBound::Yes` so that we /// can provide an appropriate diagnostic later. #[derive(Copy, Clone, PartialEq, Debug)] pub enum ExplicitLateBound { Yes, No, } #[derive(Copy, Clone, PartialEq)] pub enum IsMethodCall { Yes, No, } /// Denotes the "position" of a generic argument, indicating if it is a generic type, /// generic function or generic method call. #[derive(Copy, Clone, PartialEq)] pub(crate) enum GenericArgPosition { Type, Value, // e.g., functions MethodCall, } /// A marker denoting that the generic arguments that were /// provided did not match the respective generic parameters. #[derive(Clone, Default, Debug)] pub struct GenericArgCountMismatch { /// Indicates whether a fatal error was reported (`Some`), or just a lint (`None`). pub reported: Option, /// A list of spans of arguments provided that were not valid. pub invalid_args: Vec, } /// Decorates the result of a generic argument count mismatch /// check with whether explicit late bounds were provided. #[derive(Clone, Debug)] pub struct GenericArgCountResult { pub explicit_late_bound: ExplicitLateBound, pub correct: Result<(), GenericArgCountMismatch>, } pub trait CreateSubstsForGenericArgsCtxt<'a, 'tcx> { fn args_for_def_id(&mut self, def_id: DefId) -> (Option<&'a GenericArgs<'a>>, bool); fn provided_kind( &mut self, param: &ty::GenericParamDef, arg: &GenericArg<'_>, ) -> subst::GenericArg<'tcx>; fn inferred_kind( &mut self, substs: Option<&[subst::GenericArg<'tcx>]>, param: &ty::GenericParamDef, infer_args: bool, ) -> subst::GenericArg<'tcx>; } impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { #[instrument(level = "debug", skip(self), ret)] pub fn ast_region_to_region( &self, lifetime: &hir::Lifetime, def: Option<&ty::GenericParamDef>, ) -> ty::Region<'tcx> { let tcx = self.tcx(); let lifetime_name = |def_id| tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id)); match tcx.named_bound_var(lifetime.hir_id) { Some(rbv::ResolvedArg::StaticLifetime) => tcx.lifetimes.re_static, Some(rbv::ResolvedArg::LateBound(debruijn, index, def_id)) => { let name = lifetime_name(def_id.expect_local()); let br = ty::BoundRegion { var: ty::BoundVar::from_u32(index), kind: ty::BrNamed(def_id, name), }; ty::Region::new_late_bound(tcx, debruijn, br) } Some(rbv::ResolvedArg::EarlyBound(def_id)) => { let name = tcx.hir().ty_param_name(def_id.expect_local()); let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local()); let generics = tcx.generics_of(item_def_id); let index = generics.param_def_id_to_index[&def_id]; ty::Region::new_early_bound(tcx, ty::EarlyBoundRegion { def_id, index, name }) } Some(rbv::ResolvedArg::Free(scope, id)) => { let name = lifetime_name(id.expect_local()); ty::Region::new_free(tcx, scope, ty::BrNamed(id, name)) // (*) -- not late-bound, won't change } Some(rbv::ResolvedArg::Error(_)) => { bug!("only ty/ct should resolve as ResolvedArg::Error") } None => { self.re_infer(def, lifetime.ident.span).unwrap_or_else(|| { debug!(?lifetime, "unelided lifetime in signature"); // This indicates an illegal lifetime // elision. `resolve_lifetime` should have // reported an error in this case -- but if // not, let's error out. ty::Region::new_error_with_message( tcx, lifetime.ident.span, "unelided lifetime in signature", ) }) } } } /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`, /// returns an appropriate set of substitutions for this particular reference to `I`. pub fn ast_path_substs_for_ty( &self, span: Span, def_id: DefId, item_segment: &hir::PathSegment<'_>, ) -> SubstsRef<'tcx> { let (substs, _) = self.create_substs_for_ast_path( span, def_id, &[], item_segment, item_segment.args(), item_segment.infer_args, None, ty::BoundConstness::NotConst, ); if let Some(b) = item_segment.args().bindings.first() { prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span))); } substs } /// Given the type/lifetime/const arguments provided to some path (along with /// an implicit `Self`, if this is a trait reference), returns the complete /// set of substitutions. This may involve applying defaulted type parameters. /// Constraints on associated types are created from `create_assoc_bindings_for_generic_args`. /// /// Example: /// /// ```ignore (illustrative) /// T: std::ops::Index /// // ^1 ^^^^^^^^^^^^^^2 ^^^^3 ^^^^^^^^^^^4 /// ``` /// /// 1. The `self_ty` here would refer to the type `T`. /// 2. The path in question is the path to the trait `std::ops::Index`, /// which will have been resolved to a `def_id` /// 3. The `generic_args` contains info on the `<...>` contents. The `usize` type /// parameters are returned in the `SubstsRef`, the associated type bindings like /// `Output = u32` are returned from `create_assoc_bindings_for_generic_args`. /// /// Note that the type listing given here is *exactly* what the user provided. /// /// For (generic) associated types /// /// ```ignore (illustrative) /// as Iterable>::Iter::<'a> /// ``` /// /// We have the parent substs are the substs for the parent trait: /// `[Vec, u8]` and `generic_args` are the arguments for the associated /// type itself: `['a]`. The returned `SubstsRef` concatenates these two /// lists: `[Vec, u8, 'a]`. #[instrument(level = "debug", skip(self, span), ret)] fn create_substs_for_ast_path<'a>( &self, span: Span, def_id: DefId, parent_substs: &[subst::GenericArg<'tcx>], seg: &hir::PathSegment<'_>, generic_args: &'a hir::GenericArgs<'_>, infer_args: bool, self_ty: Option>, constness: ty::BoundConstness, ) -> (SubstsRef<'tcx>, GenericArgCountResult) { // If the type is parameterized by this region, then replace this // region with the current anon region binding (in other words, // whatever & would get replaced with). let tcx = self.tcx(); let generics = tcx.generics_of(def_id); debug!("generics: {:?}", generics); if generics.has_self { if generics.parent.is_some() { // The parent is a trait so it should have at least one subst // for the `Self` type. assert!(!parent_substs.is_empty()) } else { // This item (presumably a trait) needs a self-type. assert!(self_ty.is_some()); } } else { assert!(self_ty.is_none()); } let arg_count = check_generic_arg_count( tcx, span, def_id, seg, generics, generic_args, GenericArgPosition::Type, self_ty.is_some(), infer_args, ); // Skip processing if type has no generic parameters. // Traits always have `Self` as a generic parameter, which means they will not return early // here and so associated type bindings will be handled regardless of whether there are any // non-`Self` generic parameters. if generics.params.is_empty() { return (tcx.mk_substs(parent_substs), arg_count); } struct SubstsForAstPathCtxt<'a, 'tcx> { astconv: &'a (dyn AstConv<'tcx> + 'a), def_id: DefId, generic_args: &'a GenericArgs<'a>, span: Span, inferred_params: Vec, infer_args: bool, } impl<'a, 'tcx> CreateSubstsForGenericArgsCtxt<'a, 'tcx> for SubstsForAstPathCtxt<'a, 'tcx> { fn args_for_def_id(&mut self, did: DefId) -> (Option<&'a GenericArgs<'a>>, bool) { if did == self.def_id { (Some(self.generic_args), self.infer_args) } else { // The last component of this tuple is unimportant. (None, false) } } fn provided_kind( &mut self, param: &ty::GenericParamDef, arg: &GenericArg<'_>, ) -> subst::GenericArg<'tcx> { let tcx = self.astconv.tcx(); let mut handle_ty_args = |has_default, ty: &hir::Ty<'_>| { if has_default { tcx.check_optional_stability( param.def_id, Some(arg.hir_id()), arg.span(), None, AllowUnstable::No, |_, _| { // Default generic parameters may not be marked // with stability attributes, i.e. when the // default parameter was defined at the same time // as the rest of the type. As such, we ignore missing // stability attributes. }, ); } if let (hir::TyKind::Infer, false) = (&ty.kind, self.astconv.allow_ty_infer()) { self.inferred_params.push(ty.span); Ty::new_misc_error(tcx).into() } else { self.astconv.ast_ty_to_ty(ty).into() } }; match (¶m.kind, arg) { (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => { self.astconv.ast_region_to_region(lt, Some(param)).into() } (&GenericParamDefKind::Type { has_default, .. }, GenericArg::Type(ty)) => { handle_ty_args(has_default, ty) } (&GenericParamDefKind::Type { has_default, .. }, GenericArg::Infer(inf)) => { handle_ty_args(has_default, &inf.to_ty()) } (GenericParamDefKind::Const { .. }, GenericArg::Const(ct)) => { let did = ct.value.def_id; tcx.feed_anon_const_type(did, tcx.type_of(param.def_id)); ty::Const::from_anon_const(tcx, did).into() } (&GenericParamDefKind::Const { .. }, hir::GenericArg::Infer(inf)) => { let ty = tcx .at(self.span) .type_of(param.def_id) .no_bound_vars() .expect("const parameter types cannot be generic"); if self.astconv.allow_ty_infer() { self.astconv.ct_infer(ty, Some(param), inf.span).into() } else { self.inferred_params.push(inf.span); ty::Const::new_misc_error(tcx, ty).into() } } _ => unreachable!(), } } fn inferred_kind( &mut self, substs: Option<&[subst::GenericArg<'tcx>]>, param: &ty::GenericParamDef, infer_args: bool, ) -> subst::GenericArg<'tcx> { let tcx = self.astconv.tcx(); match param.kind { GenericParamDefKind::Lifetime => self .astconv .re_infer(Some(param), self.span) .unwrap_or_else(|| { debug!(?param, "unelided lifetime in signature"); // This indicates an illegal lifetime in a non-assoc-trait position ty::Region::new_error_with_message( tcx, self.span, "unelided lifetime in signature", ) }) .into(), GenericParamDefKind::Type { has_default, .. } => { if !infer_args && has_default { // No type parameter provided, but a default exists. let substs = substs.unwrap(); if substs.iter().any(|arg| match arg.unpack() { GenericArgKind::Type(ty) => ty.references_error(), _ => false, }) { // Avoid ICE #86756 when type error recovery goes awry. return Ty::new_misc_error(tcx).into(); } tcx.at(self.span).type_of(param.def_id).subst(tcx, substs).into() } else if infer_args { self.astconv.ty_infer(Some(param), self.span).into() } else { // We've already errored above about the mismatch. Ty::new_misc_error(tcx).into() } } GenericParamDefKind::Const { has_default } => { let ty = tcx .at(self.span) .type_of(param.def_id) .no_bound_vars() .expect("const parameter types cannot be generic"); if let Err(guar) = ty.error_reported() { return ty::Const::new_error(tcx, guar, ty).into(); } if !infer_args && has_default { tcx.const_param_default(param.def_id).subst(tcx, substs.unwrap()).into() } else { if infer_args { self.astconv.ct_infer(ty, Some(param), self.span).into() } else { // We've already errored above about the mismatch. ty::Const::new_misc_error(tcx, ty).into() } } } } } } let mut substs_ctx = SubstsForAstPathCtxt { astconv: self, def_id, span, generic_args, inferred_params: vec![], infer_args, }; let substs = create_substs_for_generic_args( tcx, def_id, parent_substs, self_ty.is_some(), self_ty, &arg_count, &mut substs_ctx, ); if let ty::BoundConstness::ConstIfConst = constness && generics.has_self && !tcx.has_attr(def_id, sym::const_trait) { tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span } ); } (substs, arg_count) } fn create_assoc_bindings_for_generic_args<'a>( &self, generic_args: &'a hir::GenericArgs<'_>, ) -> Vec> { // Convert associated-type bindings or constraints into a separate vector. // Example: Given this: // // T: Iterator // // The `T` is passed in as a self-type; the `Item = u32` is // not a "type parameter" of the `Iterator` trait, but rather // a restriction on `::Item`, so it is passed // back separately. let assoc_bindings = generic_args .bindings .iter() .map(|binding| { let kind = match &binding.kind { hir::TypeBindingKind::Equality { term } => match term { hir::Term::Ty(ty) => { ConvertedBindingKind::Equality(self.ast_ty_to_ty(ty).into()) } hir::Term::Const(c) => { let c = Const::from_anon_const(self.tcx(), c.def_id); ConvertedBindingKind::Equality(c.into()) } }, hir::TypeBindingKind::Constraint { bounds } => { ConvertedBindingKind::Constraint(bounds) } }; ConvertedBinding { hir_id: binding.hir_id, item_name: binding.ident, kind, gen_args: binding.gen_args, span: binding.span, } }) .collect(); assoc_bindings } pub fn create_substs_for_associated_item( &self, span: Span, item_def_id: DefId, item_segment: &hir::PathSegment<'_>, parent_substs: SubstsRef<'tcx>, ) -> SubstsRef<'tcx> { debug!( "create_substs_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}", span, item_def_id, item_segment ); let (args, _) = self.create_substs_for_ast_path( span, item_def_id, parent_substs, item_segment, item_segment.args(), item_segment.infer_args, None, ty::BoundConstness::NotConst, ); if let Some(b) = item_segment.args().bindings.first() { prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span))); } args } /// Instantiates the path for the given trait reference, assuming that it's /// bound to a valid trait type. Returns the `DefId` of the defining trait. /// The type _cannot_ be a type other than a trait type. /// /// If the `projections` argument is `None`, then assoc type bindings like `Foo` /// are disallowed. Otherwise, they are pushed onto the vector given. pub fn instantiate_mono_trait_ref( &self, trait_ref: &hir::TraitRef<'_>, self_ty: Ty<'tcx>, constness: ty::BoundConstness, ) -> ty::TraitRef<'tcx> { self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {}); self.ast_path_to_mono_trait_ref( trait_ref.path.span, trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()), self_ty, trait_ref.path.segments.last().unwrap(), true, constness, ) } fn instantiate_poly_trait_ref_inner( &self, hir_id: hir::HirId, span: Span, binding_span: Option, constness: ty::BoundConstness, polarity: ty::ImplPolarity, bounds: &mut Bounds<'tcx>, speculative: bool, trait_ref_span: Span, trait_def_id: DefId, trait_segment: &hir::PathSegment<'_>, args: &GenericArgs<'_>, infer_args: bool, self_ty: Ty<'tcx>, only_self_bounds: OnlySelfBounds, ) -> GenericArgCountResult { let (substs, arg_count) = self.create_substs_for_ast_path( trait_ref_span, trait_def_id, &[], trait_segment, args, infer_args, Some(self_ty), constness, ); let tcx = self.tcx(); let bound_vars = tcx.late_bound_vars(hir_id); debug!(?bound_vars); let assoc_bindings = self.create_assoc_bindings_for_generic_args(args); let poly_trait_ref = ty::Binder::bind_with_vars(ty::TraitRef::new(tcx, trait_def_id, substs), bound_vars); debug!(?poly_trait_ref, ?assoc_bindings); bounds.push_trait_bound(tcx, poly_trait_ref, span, constness, polarity); let mut dup_bindings = FxHashMap::default(); for binding in &assoc_bindings { // Don't register additional associated type bounds for negative bounds, // since we should have emitten an error for them earlier, and they will // not be well-formed! if polarity == ty::ImplPolarity::Negative { self.tcx() .sess .delay_span_bug(binding.span, "negative trait bounds should not have bindings"); continue; } // Specify type to assert that error was already reported in `Err` case. let _: Result<_, ErrorGuaranteed> = self.add_predicates_for_ast_type_binding( hir_id, poly_trait_ref, binding, bounds, speculative, &mut dup_bindings, binding_span.unwrap_or(binding.span), constness, only_self_bounds, polarity, ); // Okay to ignore `Err` because of `ErrorGuaranteed` (see above). } arg_count } /// Given a trait bound like `Debug`, applies that trait bound the given self-type to construct /// a full trait reference. The resulting trait reference is returned. This may also generate /// auxiliary bounds, which are added to `bounds`. /// /// Example: /// /// ```ignore (illustrative) /// poly_trait_ref = Iterator /// self_ty = Foo /// ``` /// /// this would return `Foo: Iterator` and add `::Item = u32` into `bounds`. /// /// **A note on binders:** against our usual convention, there is an implied bounder around /// the `self_ty` and `poly_trait_ref` parameters here. So they may reference bound regions. /// If for example you had `for<'a> Foo<'a>: Bar<'a>`, then the `self_ty` would be `Foo<'a>` /// where `'a` is a bound region at depth 0. Similarly, the `poly_trait_ref` would be /// `Bar<'a>`. The returned poly-trait-ref will have this binder instantiated explicitly, /// however. #[instrument(level = "debug", skip(self, span, constness, bounds, speculative))] pub(crate) fn instantiate_poly_trait_ref( &self, trait_ref: &hir::TraitRef<'_>, span: Span, constness: ty::BoundConstness, polarity: ty::ImplPolarity, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, speculative: bool, only_self_bounds: OnlySelfBounds, ) -> GenericArgCountResult { let hir_id = trait_ref.hir_ref_id; let binding_span = None; let trait_ref_span = trait_ref.path.span; let trait_def_id = trait_ref.trait_def_id().unwrap_or_else(|| FatalError.raise()); let trait_segment = trait_ref.path.segments.last().unwrap(); let args = trait_segment.args(); let infer_args = trait_segment.infer_args; self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1.iter(), |_| {}); self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, false); self.instantiate_poly_trait_ref_inner( hir_id, span, binding_span, constness, polarity, bounds, speculative, trait_ref_span, trait_def_id, trait_segment, args, infer_args, self_ty, only_self_bounds, ) } pub(crate) fn instantiate_lang_item_trait_ref( &self, lang_item: hir::LangItem, span: Span, hir_id: hir::HirId, args: &GenericArgs<'_>, self_ty: Ty<'tcx>, bounds: &mut Bounds<'tcx>, only_self_bounds: OnlySelfBounds, ) { let binding_span = Some(span); let constness = ty::BoundConstness::NotConst; let speculative = false; let trait_ref_span = span; let trait_def_id = self.tcx().require_lang_item(lang_item, Some(span)); let trait_segment = &hir::PathSegment::invalid(); let infer_args = false; self.instantiate_poly_trait_ref_inner( hir_id, span, binding_span, constness, ty::ImplPolarity::Positive, bounds, speculative, trait_ref_span, trait_def_id, trait_segment, args, infer_args, self_ty, only_self_bounds, ); } fn ast_path_to_mono_trait_ref( &self, span: Span, trait_def_id: DefId, self_ty: Ty<'tcx>, trait_segment: &hir::PathSegment<'_>, is_impl: bool, constness: ty::BoundConstness, ) -> ty::TraitRef<'tcx> { let (substs, _) = self.create_substs_for_ast_trait_ref( span, trait_def_id, self_ty, trait_segment, is_impl, constness, ); if let Some(b) = trait_segment.args().bindings.first() { prohibit_assoc_ty_binding(self.tcx(), b.span, Some((trait_segment, span))); } ty::TraitRef::new(self.tcx(), trait_def_id, substs) } #[instrument(level = "debug", skip(self, span))] fn create_substs_for_ast_trait_ref<'a>( &self, span: Span, trait_def_id: DefId, self_ty: Ty<'tcx>, trait_segment: &'a hir::PathSegment<'a>, is_impl: bool, constness: ty::BoundConstness, ) -> (SubstsRef<'tcx>, GenericArgCountResult) { self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, is_impl); self.create_substs_for_ast_path( span, trait_def_id, &[], trait_segment, trait_segment.args(), trait_segment.infer_args, Some(self_ty), constness, ) } fn trait_defines_associated_item_named( &self, trait_def_id: DefId, assoc_kind: ty::AssocKind, assoc_name: Ident, ) -> bool { self.tcx() .associated_items(trait_def_id) .find_by_name_and_kind(self.tcx(), assoc_name, assoc_kind, trait_def_id) .is_some() } fn ast_path_to_ty( &self, span: Span, did: DefId, item_segment: &hir::PathSegment<'_>, ) -> Ty<'tcx> { let substs = self.ast_path_substs_for_ty(span, did, item_segment); let ty = self.tcx().at(span).type_of(did); if matches!(self.tcx().def_kind(did), DefKind::TyAlias) && (ty.skip_binder().has_opaque_types() || self.tcx().features().lazy_type_alias) { // Type aliases referring to types that contain opaque types (but aren't just directly // referencing a single opaque type) get encoded as a type alias that normalization will // then actually instantiate the where bounds of. let alias_ty = self.tcx().mk_alias_ty(did, substs); Ty::new_alias(self.tcx(), ty::Weak, alias_ty) } else { ty.subst(self.tcx(), substs) } } fn report_ambiguous_associated_type( &self, span: Span, types: &[String], traits: &[String], name: Symbol, ) -> ErrorGuaranteed { let mut err = struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type"); if self .tcx() .resolutions(()) .confused_type_with_std_module .keys() .any(|full_span| full_span.contains(span)) { err.span_suggestion_verbose( span.shrink_to_lo(), "you are looking for the module in `std`, not the primitive type", "std::", Applicability::MachineApplicable, ); } else { match (types, traits) { ([], []) => { err.span_suggestion_verbose( span, format!( "if there were a type named `Type` that implements a trait named \ `Trait` with associated type `{name}`, you could use the \ fully-qualified path", ), format!("::{name}"), Applicability::HasPlaceholders, ); } ([], [trait_str]) => { err.span_suggestion_verbose( span, format!( "if there were a type named `Example` that implemented `{trait_str}`, \ you could use the fully-qualified path", ), format!("::{name}"), Applicability::HasPlaceholders, ); } ([], traits) => { err.span_suggestions( span, format!( "if there were a type named `Example` that implemented one of the \ traits with associated type `{name}`, you could use the \ fully-qualified path", ), traits .iter() .map(|trait_str| format!("::{name}")) .collect::>(), Applicability::HasPlaceholders, ); } ([type_str], []) => { err.span_suggestion_verbose( span, format!( "if there were a trait named `Example` with associated type `{name}` \ implemented for `{type_str}`, you could use the fully-qualified path", ), format!("<{type_str} as Example>::{name}"), Applicability::HasPlaceholders, ); } (types, []) => { err.span_suggestions( span, format!( "if there were a trait named `Example` with associated type `{name}` \ implemented for one of the types, you could use the fully-qualified \ path", ), types .into_iter() .map(|type_str| format!("<{type_str} as Example>::{name}")), Applicability::HasPlaceholders, ); } (types, traits) => { let mut suggestions = vec![]; for type_str in types { for trait_str in traits { suggestions.push(format!("<{type_str} as {trait_str}>::{name}")); } } err.span_suggestions( span, "use the fully-qualified path", suggestions, Applicability::MachineApplicable, ); } } } err.emit() } // Search for a bound on a type parameter which includes the associated item // given by `assoc_name`. `ty_param_def_id` is the `DefId` of the type parameter // This function will fail if there are no suitable bounds or there is // any ambiguity. fn find_bound_for_assoc_item( &self, ty_param_def_id: LocalDefId, assoc_name: Ident, span: Span, ) -> Result, ErrorGuaranteed> { let tcx = self.tcx(); debug!( "find_bound_for_assoc_item(ty_param_def_id={:?}, assoc_name={:?}, span={:?})", ty_param_def_id, assoc_name, span, ); let predicates = &self.get_type_parameter_bounds(span, ty_param_def_id, assoc_name).predicates; debug!("find_bound_for_assoc_item: predicates={:#?}", predicates); let param_name = tcx.hir().ty_param_name(ty_param_def_id); self.one_bound_for_assoc_type( || { traits::transitive_bounds_that_define_assoc_item( tcx, predicates .iter() .filter_map(|(p, _)| Some(p.as_trait_clause()?.map_bound(|t| t.trait_ref))), assoc_name, ) }, param_name, assoc_name, span, None, ) } // Checks that `bounds` contains exactly one element and reports appropriate // errors otherwise. #[instrument(level = "debug", skip(self, all_candidates, ty_param_name, is_equality), ret)] fn one_bound_for_assoc_type( &self, all_candidates: impl Fn() -> I, ty_param_name: impl Display, assoc_name: Ident, span: Span, is_equality: Option>, ) -> Result, ErrorGuaranteed> where I: Iterator>, { let mut matching_candidates = all_candidates().filter(|r| { self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Type, assoc_name) }); let mut const_candidates = all_candidates().filter(|r| { self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Const, assoc_name) }); let (bound, next_cand) = match (matching_candidates.next(), const_candidates.next()) { (Some(bound), _) => (bound, matching_candidates.next()), (None, Some(bound)) => (bound, const_candidates.next()), (None, None) => { let reported = self.complain_about_assoc_type_not_found( all_candidates, &ty_param_name.to_string(), assoc_name, span, ); return Err(reported); } }; debug!(?bound); if let Some(bound2) = next_cand { debug!(?bound2); let bounds = IntoIterator::into_iter([bound, bound2]).chain(matching_candidates); let mut err = if is_equality.is_some() { // More specific Error Index entry. struct_span_err!( self.tcx().sess, span, E0222, "ambiguous associated type `{}` in bounds of `{}`", assoc_name, ty_param_name ) } else { struct_span_err!( self.tcx().sess, span, E0221, "ambiguous associated type `{}` in bounds of `{}`", assoc_name, ty_param_name ) }; err.span_label(span, format!("ambiguous associated type `{}`", assoc_name)); let mut where_bounds = vec![]; for bound in bounds { let bound_id = bound.def_id(); let bound_span = self .tcx() .associated_items(bound_id) .find_by_name_and_kind(self.tcx(), assoc_name, ty::AssocKind::Type, bound_id) .and_then(|item| self.tcx().hir().span_if_local(item.def_id)); if let Some(bound_span) = bound_span { err.span_label( bound_span, format!( "ambiguous `{}` from `{}`", assoc_name, bound.print_only_trait_path(), ), ); if let Some(constraint) = &is_equality { where_bounds.push(format!( " T: {trait}::{assoc} = {constraint}", trait=bound.print_only_trait_path(), assoc=assoc_name, constraint=constraint, )); } else { err.span_suggestion_verbose( span.with_hi(assoc_name.span.lo()), "use fully qualified syntax to disambiguate", format!("<{} as {}>::", ty_param_name, bound.print_only_trait_path()), Applicability::MaybeIncorrect, ); } } else { err.note(format!( "associated type `{}` could derive from `{}`", ty_param_name, bound.print_only_trait_path(), )); } } if !where_bounds.is_empty() { err.help(format!( "consider introducing a new type parameter `T` and adding `where` constraints:\ \n where\n T: {},\n{}", ty_param_name, where_bounds.join(",\n"), )); } let reported = err.emit(); if !where_bounds.is_empty() { return Err(reported); } } Ok(bound) } #[instrument(level = "debug", skip(self, all_candidates, ty_name), ret)] fn one_bound_for_assoc_method( &self, all_candidates: impl Iterator>, ty_name: impl Display, assoc_name: Ident, span: Span, ) -> Result, ErrorGuaranteed> { let mut matching_candidates = all_candidates.filter(|r| { self.trait_defines_associated_item_named(r.def_id(), ty::AssocKind::Fn, assoc_name) }); let candidate = match matching_candidates.next() { Some(candidate) => candidate, None => { return Err(self.tcx().sess.emit_err( crate::errors::ReturnTypeNotationMissingMethod { span, ty_name: ty_name.to_string(), assoc_name: assoc_name.name, }, )); } }; if let Some(conflicting_candidate) = matching_candidates.next() { return Err(self.tcx().sess.emit_err( crate::errors::ReturnTypeNotationConflictingBound { span, ty_name: ty_name.to_string(), assoc_name: assoc_name.name, first_bound: candidate.print_only_trait_path(), second_bound: conflicting_candidate.print_only_trait_path(), }, )); } Ok(candidate) } // Create a type from a path to an associated type or to an enum variant. // For a path `A::B::C::D`, `qself_ty` and `qself_def` are the type and def for `A::B::C` // and item_segment is the path segment for `D`. We return a type and a def for // the whole path. // Will fail except for `T::A` and `Self::A`; i.e., if `qself_ty`/`qself_def` are not a type // parameter or `Self`. // NOTE: When this function starts resolving `Trait::AssocTy` successfully // it should also start reporting the `BARE_TRAIT_OBJECTS` lint. #[instrument(level = "debug", skip(self, hir_ref_id, span, qself, assoc_segment), fields(assoc_ident=?assoc_segment.ident), ret)] pub fn associated_path_to_ty( &self, hir_ref_id: hir::HirId, span: Span, qself_ty: Ty<'tcx>, qself: &hir::Ty<'_>, assoc_segment: &hir::PathSegment<'_>, permit_variants: bool, ) -> Result<(Ty<'tcx>, DefKind, DefId), ErrorGuaranteed> { let tcx = self.tcx(); let assoc_ident = assoc_segment.ident; let qself_res = if let hir::TyKind::Path(hir::QPath::Resolved(_, path)) = &qself.kind { path.res } else { Res::Err }; // Check if we have an enum variant or an inherent associated type. let mut variant_resolution = None; if let Some(adt_def) = self.probe_adt(span, qself_ty) { if adt_def.is_enum() { let variant_def = adt_def .variants() .iter() .find(|vd| tcx.hygienic_eq(assoc_ident, vd.ident(tcx), adt_def.did())); if let Some(variant_def) = variant_def { if permit_variants { tcx.check_stability(variant_def.def_id, Some(hir_ref_id), span, None); self.prohibit_generics(slice::from_ref(assoc_segment).iter(), |err| { err.note("enum variants can't have type parameters"); let type_name = tcx.item_name(adt_def.did()); let msg = format!( "you might have meant to specify type parameters on enum \ `{type_name}`" ); let Some(args) = assoc_segment.args else { return; }; // Get the span of the generics args *including* the leading `::`. let args_span = assoc_segment.ident.span.shrink_to_hi().to(args.span_ext); if tcx.generics_of(adt_def.did()).count() == 0 { // FIXME(estebank): we could also verify that the arguments being // work for the `enum`, instead of just looking if it takes *any*. err.span_suggestion_verbose( args_span, format!("{type_name} doesn't have generic parameters"), "", Applicability::MachineApplicable, ); return; } let Ok(snippet) = tcx.sess.source_map().span_to_snippet(args_span) else { err.note(msg); return; }; let (qself_sugg_span, is_self) = if let hir::TyKind::Path( hir::QPath::Resolved(_, path) ) = &qself.kind { // If the path segment already has type params, we want to overwrite // them. match &path.segments { // `segment` is the previous to last element on the path, // which would normally be the `enum` itself, while the last // `_` `PathSegment` corresponds to the variant. [.., hir::PathSegment { ident, args, res: Res::Def(DefKind::Enum, _), .. }, _] => ( // We need to include the `::` in `Type::Variant::` // to point the span to `::`, not just ``. ident.span.shrink_to_hi().to(args.map_or( ident.span.shrink_to_hi(), |a| a.span_ext)), false, ), [segment] => ( // We need to include the `::` in `Type::Variant::` // to point the span to `::`, not just ``. segment.ident.span.shrink_to_hi().to(segment.args.map_or( segment.ident.span.shrink_to_hi(), |a| a.span_ext)), kw::SelfUpper == segment.ident.name, ), _ => { err.note(msg); return; } } } else { err.note(msg); return; }; let suggestion = vec![ if is_self { // Account for people writing `Self::Variant::`, where // `Self` is the enum, and suggest replacing `Self` with the // appropriate type: `Type::::Variant`. (qself.span, format!("{type_name}{snippet}")) } else { (qself_sugg_span, snippet) }, (args_span, String::new()), ]; err.multipart_suggestion_verbose( msg, suggestion, Applicability::MaybeIncorrect, ); }); return Ok((qself_ty, DefKind::Variant, variant_def.def_id)); } else { variant_resolution = Some(variant_def.def_id); } } } if let Some((ty, did)) = self.lookup_inherent_assoc_ty( assoc_ident, assoc_segment, adt_def.did(), qself_ty, hir_ref_id, span, )? { return Ok((ty, DefKind::AssocTy, did)); } } // Find the type of the associated item, and the trait where the associated // item is declared. let bound = match (&qself_ty.kind(), qself_res) { (_, Res::SelfTyAlias { alias_to: impl_def_id, is_trait_impl: true, .. }) => { // `Self` in an impl of a trait -- we have a concrete self type and a // trait reference. let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) else { // A cycle error occurred, most likely. let guar = tcx.sess.delay_span_bug(span, "expected cycle error"); return Err(guar); }; self.one_bound_for_assoc_type( || traits::supertraits(tcx, ty::Binder::dummy(trait_ref.subst_identity())), kw::SelfUpper, assoc_ident, span, None, )? } ( &ty::Param(_), Res::SelfTyParam { trait_: param_did } | Res::Def(DefKind::TyParam, param_did), ) => self.find_bound_for_assoc_item(param_did.expect_local(), assoc_ident, span)?, _ => { let reported = if variant_resolution.is_some() { // Variant in type position let msg = format!("expected type, found variant `{}`", assoc_ident); tcx.sess.span_err(span, msg) } else if qself_ty.is_enum() { let mut err = struct_span_err!( tcx.sess, assoc_ident.span, E0599, "no variant named `{}` found for enum `{}`", assoc_ident, qself_ty, ); let adt_def = qself_ty.ty_adt_def().expect("enum is not an ADT"); if let Some(suggested_name) = find_best_match_for_name( &adt_def .variants() .iter() .map(|variant| variant.name) .collect::>(), assoc_ident.name, None, ) { err.span_suggestion( assoc_ident.span, "there is a variant with a similar name", suggested_name, Applicability::MaybeIncorrect, ); } else { err.span_label( assoc_ident.span, format!("variant not found in `{}`", qself_ty), ); } if let Some(sp) = tcx.hir().span_if_local(adt_def.did()) { err.span_label(sp, format!("variant `{}` not found here", assoc_ident)); } err.emit() } else if let Err(reported) = qself_ty.error_reported() { reported } else if let ty::Alias(ty::Opaque, alias_ty) = qself_ty.kind() { // `::Assoc` makes no sense. struct_span_err!( tcx.sess, tcx.def_span(alias_ty.def_id), E0667, "`impl Trait` is not allowed in path parameters" ) .emit() // Already reported in an earlier stage. } else { let traits: Vec<_> = self.probe_traits_that_match_assoc_ty(qself_ty, assoc_ident); // Don't print `TyErr` to the user. self.report_ambiguous_associated_type( span, &[qself_ty.to_string()], &traits, assoc_ident.name, ) }; return Err(reported); } }; let trait_did = bound.def_id(); let Some(assoc_ty_did) = self.lookup_assoc_ty(assoc_ident, hir_ref_id, span, trait_did) else { // Assume that if it's not matched, there must be a const defined with the same name // but it was used in a type position. let msg = format!("found associated const `{assoc_ident}` when type was expected"); let guar = tcx.sess.struct_span_err(span, msg).emit(); return Err(guar); }; let ty = self.projected_ty_from_poly_trait_ref(span, assoc_ty_did, assoc_segment, bound); if let Some(variant_def_id) = variant_resolution { tcx.struct_span_lint_hir( AMBIGUOUS_ASSOCIATED_ITEMS, hir_ref_id, span, "ambiguous associated item", |lint| { let mut could_refer_to = |kind: DefKind, def_id, also| { let note_msg = format!( "`{}` could{} refer to the {} defined here", assoc_ident, also, tcx.def_kind_descr(kind, def_id) ); lint.span_note(tcx.def_span(def_id), note_msg); }; could_refer_to(DefKind::Variant, variant_def_id, ""); could_refer_to(DefKind::AssocTy, assoc_ty_did, " also"); lint.span_suggestion( span, "use fully-qualified syntax", format!("<{} as {}>::{}", qself_ty, tcx.item_name(trait_did), assoc_ident), Applicability::MachineApplicable, ); lint }, ); } Ok((ty, DefKind::AssocTy, assoc_ty_did)) } fn lookup_inherent_assoc_ty( &self, name: Ident, segment: &hir::PathSegment<'_>, adt_did: DefId, self_ty: Ty<'tcx>, block: hir::HirId, span: Span, ) -> Result, DefId)>, ErrorGuaranteed> { let tcx = self.tcx(); // Don't attempt to look up inherent associated types when the feature is not enabled. // Theoretically it'd be fine to do so since we feature-gate their definition site. // However, due to current limitations of the implementation (caused by us performing // selection in AstConv), IATs can lead to cycle errors (#108491, #110106) which mask the // feature-gate error, needlessly confusing users that use IATs by accident (#113265). if !tcx.features().inherent_associated_types { return Ok(None); } let candidates: Vec<_> = tcx .inherent_impls(adt_did) .iter() .filter_map(|&impl_| Some((impl_, self.lookup_assoc_ty_unchecked(name, block, impl_)?))) .collect(); if candidates.is_empty() { return Ok(None); } // // Select applicable inherent associated type candidates modulo regions. // // In contexts that have no inference context, just make a new one. // We do need a local variable to store it, though. let infcx_; let infcx = match self.infcx() { Some(infcx) => infcx, None => { assert!(!self_ty.has_infer()); infcx_ = tcx.infer_ctxt().ignoring_regions().build(); &infcx_ } }; // FIXME(inherent_associated_types): Acquiring the ParamEnv this early leads to cycle errors // when inside of an ADT (#108491) or where clause. let param_env = tcx.param_env(block.owner); let cause = ObligationCause::misc(span, block.owner.def_id); let mut fulfillment_errors = Vec::new(); let mut applicable_candidates: Vec<_> = infcx.probe(|_| { // Regions are not considered during selection. let self_ty = self_ty .fold_with(&mut BoundVarEraser { tcx, universe: infcx.create_next_universe() }); struct BoundVarEraser<'tcx> { tcx: TyCtxt<'tcx>, universe: ty::UniverseIndex, } // FIXME(non_lifetime_binders): Don't assign the same universe to each placeholder. impl<'tcx> TypeFolder> for BoundVarEraser<'tcx> { fn interner(&self) -> TyCtxt<'tcx> { self.tcx } fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { if r.is_late_bound() { self.tcx.lifetimes.re_erased } else { r } } fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { match *ty.kind() { ty::Bound(_, bv) => Ty::new_placeholder( self.tcx, ty::PlaceholderType { universe: self.universe, bound: bv }, ), _ => ty.super_fold_with(self), } } fn fold_const( &mut self, ct: ty::Const<'tcx>, ) -> as rustc_type_ir::Interner>::Const { assert!(!ct.ty().has_escaping_bound_vars()); match ct.kind() { ty::ConstKind::Bound(_, bv) => ty::Const::new_placeholder( self.tcx, ty::PlaceholderConst { universe: self.universe, bound: bv }, ct.ty(), ), _ => ct.super_fold_with(self), } } } let InferOk { value: self_ty, obligations } = infcx.at(&cause, param_env).normalize(self_ty); candidates .iter() .copied() .filter(|&(impl_, _)| { infcx.probe(|_| { let ocx = ObligationCtxt::new(&infcx); ocx.register_obligations(obligations.clone()); let impl_substs = infcx.fresh_substs_for_item(span, impl_); let impl_ty = tcx.type_of(impl_).subst(tcx, impl_substs); let impl_ty = ocx.normalize(&cause, param_env, impl_ty); // Check that the self types can be related. // FIXME(inherent_associated_types): Should we use `eq` here? Method probing uses // `sup` for this situtation, too. What for? To constrain inference variables? if ocx.sup(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err() { return false; } // Check whether the impl imposes obligations we have to worry about. let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_substs); let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds); let impl_obligations = traits::predicates_for_generics( |_, _| cause.clone(), param_env, impl_bounds, ); ocx.register_obligations(impl_obligations); let mut errors = ocx.select_where_possible(); if !errors.is_empty() { fulfillment_errors.append(&mut errors); return false; } true }) }) .collect() }); if applicable_candidates.len() > 1 { return Err(self.complain_about_ambiguous_inherent_assoc_type( name, applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(), span, )); } if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() { self.check_assoc_ty(assoc_item, name, def_scope, block, span); // FIXME(fmease): Currently creating throwaway `parent_substs` to please // `create_substs_for_associated_item`. Modify the latter instead (or sth. similar) to // not require the parent substs logic. let parent_substs = InternalSubsts::identity_for_item(tcx, impl_); let substs = self.create_substs_for_associated_item(span, assoc_item, segment, parent_substs); let substs = tcx.mk_substs_from_iter( std::iter::once(ty::GenericArg::from(self_ty)) .chain(substs.into_iter().skip(parent_substs.len())), ); let ty = Ty::new_alias(tcx, ty::Inherent, tcx.mk_alias_ty(assoc_item, substs)); return Ok(Some((ty, assoc_item))); } Err(self.complain_about_inherent_assoc_type_not_found( name, self_ty, candidates, fulfillment_errors, span, )) } fn lookup_assoc_ty( &self, name: Ident, block: hir::HirId, span: Span, scope: DefId, ) -> Option { let (item, def_scope) = self.lookup_assoc_ty_unchecked(name, block, scope)?; self.check_assoc_ty(item, name, def_scope, block, span); Some(item) } fn lookup_assoc_ty_unchecked( &self, name: Ident, block: hir::HirId, scope: DefId, ) -> Option<(DefId, DefId)> { let tcx = self.tcx(); let (ident, def_scope) = tcx.adjust_ident_and_get_scope(name, scope, block); // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead // of calling `find_by_name_and_kind`. let item = tcx.associated_items(scope).in_definition_order().find(|i| { i.kind.namespace() == Namespace::TypeNS && i.ident(tcx).normalize_to_macros_2_0() == ident })?; Some((item.def_id, def_scope)) } fn check_assoc_ty( &self, item: DefId, name: Ident, def_scope: DefId, block: hir::HirId, span: Span, ) { let tcx = self.tcx(); let kind = DefKind::AssocTy; if !tcx.visibility(item).is_accessible_from(def_scope, tcx) { let kind = tcx.def_kind_descr(kind, item); let msg = format!("{kind} `{name}` is private"); let def_span = tcx.def_span(item); tcx.sess .struct_span_err_with_code(span, msg, rustc_errors::error_code!(E0624)) .span_label(span, format!("private {kind}")) .span_label(def_span, format!("{kind} defined here")) .emit(); } tcx.check_stability(item, Some(block), span, None); } fn probe_traits_that_match_assoc_ty( &self, qself_ty: Ty<'tcx>, assoc_ident: Ident, ) -> Vec { let tcx = self.tcx(); // In contexts that have no inference context, just make a new one. // We do need a local variable to store it, though. let infcx_; let infcx = if let Some(infcx) = self.infcx() { infcx } else { assert!(!qself_ty.has_infer()); infcx_ = tcx.infer_ctxt().build(); &infcx_ }; tcx.all_traits() .filter(|trait_def_id| { // Consider only traits with the associated type tcx.associated_items(*trait_def_id) .in_definition_order() .any(|i| { i.kind.namespace() == Namespace::TypeNS && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident && matches!(i.kind, ty::AssocKind::Type) }) // Consider only accessible traits && tcx.visibility(*trait_def_id) .is_accessible_from(self.item_def_id(), tcx) && tcx.all_impls(*trait_def_id) .any(|impl_def_id| { let trait_ref = tcx.impl_trait_ref(impl_def_id); trait_ref.is_some_and(|trait_ref| { let impl_ = trait_ref.subst( tcx, infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id), ); let value = tcx.fold_regions(qself_ty, |_, _| tcx.lifetimes.re_erased); // FIXME: Don't bother dealing with non-lifetime binders here... if value.has_escaping_bound_vars() { return false; } infcx .can_eq( ty::ParamEnv::empty(), impl_.self_ty(), value, ) }) && tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative }) }) .map(|trait_def_id| tcx.def_path_str(trait_def_id)) .collect() } fn qpath_to_ty( &self, span: Span, opt_self_ty: Option>, item_def_id: DefId, trait_segment: &hir::PathSegment<'_>, item_segment: &hir::PathSegment<'_>, constness: ty::BoundConstness, ) -> Ty<'tcx> { let tcx = self.tcx(); let trait_def_id = tcx.parent(item_def_id); debug!("qpath_to_ty: trait_def_id={:?}", trait_def_id); let Some(self_ty) = opt_self_ty else { let path_str = tcx.def_path_str(trait_def_id); let def_id = self.item_def_id(); debug!("qpath_to_ty: self.item_def_id()={:?}", def_id); let parent_def_id = def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id)) .map(|hir_id| tcx.hir().get_parent_item(hir_id).to_def_id()); debug!("qpath_to_ty: parent_def_id={:?}", parent_def_id); // If the trait in segment is the same as the trait defining the item, // use the `` syntax in the error. let is_part_of_self_trait_constraints = def_id == trait_def_id; let is_part_of_fn_in_self_trait = parent_def_id == Some(trait_def_id); let type_names = if is_part_of_self_trait_constraints || is_part_of_fn_in_self_trait { vec!["Self".to_string()] } else { // Find all the types that have an `impl` for the trait. tcx.all_impls(trait_def_id) .filter(|impl_def_id| { // Consider only accessible traits tcx.visibility(trait_def_id).is_accessible_from(self.item_def_id(), tcx) && tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative }) .filter_map(|impl_def_id| tcx.impl_trait_ref(impl_def_id)) .map(|impl_| impl_.subst_identity().self_ty()) // We don't care about blanket impls. .filter(|self_ty| !self_ty.has_non_region_param()) .map(|self_ty| tcx.erase_regions(self_ty).to_string()) .collect() }; // FIXME: also look at `tcx.generics_of(self.item_def_id()).params` any that // references the trait. Relevant for the first case in // `src/test/ui/associated-types/associated-types-in-ambiguous-context.rs` let reported = self.report_ambiguous_associated_type( span, &type_names, &[path_str], item_segment.ident.name, ); return Ty::new_error(tcx,reported) }; debug!("qpath_to_ty: self_type={:?}", self_ty); let trait_ref = self.ast_path_to_mono_trait_ref( span, trait_def_id, self_ty, trait_segment, false, constness, ); let item_substs = self.create_substs_for_associated_item( span, item_def_id, item_segment, trait_ref.substs, ); debug!("qpath_to_ty: trait_ref={:?}", trait_ref); Ty::new_projection(tcx, item_def_id, item_substs) } pub fn prohibit_generics<'a>( &self, segments: impl Iterator> + Clone, extend: impl Fn(&mut Diagnostic), ) -> bool { let args = segments.clone().flat_map(|segment| segment.args().args); let (lt, ty, ct, inf) = args.clone().fold((false, false, false, false), |(lt, ty, ct, inf), arg| match arg { hir::GenericArg::Lifetime(_) => (true, ty, ct, inf), hir::GenericArg::Type(_) => (lt, true, ct, inf), hir::GenericArg::Const(_) => (lt, ty, true, inf), hir::GenericArg::Infer(_) => (lt, ty, ct, true), }); let mut emitted = false; if lt || ty || ct || inf { let types_and_spans: Vec<_> = segments .clone() .flat_map(|segment| { if segment.args().args.is_empty() { None } else { Some(( match segment.res { Res::PrimTy(ty) => format!("{} `{}`", segment.res.descr(), ty.name()), Res::Def(_, def_id) if let Some(name) = self.tcx().opt_item_name(def_id) => { format!("{} `{name}`", segment.res.descr()) } Res::Err => "this type".to_string(), _ => segment.res.descr().to_string(), }, segment.ident.span, )) } }) .collect(); let this_type = match &types_and_spans[..] { [.., _, (last, _)] => format!( "{} and {last}", types_and_spans[..types_and_spans.len() - 1] .iter() .map(|(x, _)| x.as_str()) .intersperse(&", ") .collect::() ), [(only, _)] => only.to_string(), [] => "this type".to_string(), }; let arg_spans: Vec = args.map(|arg| arg.span()).collect(); let mut kinds = Vec::with_capacity(4); if lt { kinds.push("lifetime"); } if ty { kinds.push("type"); } if ct { kinds.push("const"); } if inf { kinds.push("generic"); } let (kind, s) = match kinds[..] { [.., _, last] => ( format!( "{} and {last}", kinds[..kinds.len() - 1] .iter() .map(|&x| x) .intersperse(", ") .collect::() ), "s", ), [only] => (only.to_string(), ""), [] => unreachable!(), }; let last_span = *arg_spans.last().unwrap(); let span: MultiSpan = arg_spans.into(); let mut err = struct_span_err!( self.tcx().sess, span, E0109, "{kind} arguments are not allowed on {this_type}", ); err.span_label(last_span, format!("{kind} argument{s} not allowed")); for (what, span) in types_and_spans { err.span_label(span, format!("not allowed on {what}")); } extend(&mut err); err.emit(); emitted = true; } for segment in segments { // Only emit the first error to avoid overloading the user with error messages. if let Some(b) = segment.args().bindings.first() { prohibit_assoc_ty_binding(self.tcx(), b.span, None); return true; } } emitted } // FIXME(eddyb, varkor) handle type paths here too, not just value ones. pub fn def_ids_for_value_path_segments( &self, segments: &[hir::PathSegment<'_>], self_ty: Option>, kind: DefKind, def_id: DefId, span: Span, ) -> Vec { // We need to extract the type parameters supplied by the user in // the path `path`. Due to the current setup, this is a bit of a // tricky-process; the problem is that resolve only tells us the // end-point of the path resolution, and not the intermediate steps. // Luckily, we can (at least for now) deduce the intermediate steps // just from the end-point. // // There are basically five cases to consider: // // 1. Reference to a constructor of a struct: // // struct Foo(...) // // In this case, the parameters are declared in the type space. // // 2. Reference to a constructor of an enum variant: // // enum E { Foo(...) } // // In this case, the parameters are defined in the type space, // but may be specified either on the type or the variant. // // 3. Reference to a fn item or a free constant: // // fn foo() { } // // In this case, the path will again always have the form // `a::b::foo::` where only the final segment should have // type parameters. However, in this case, those parameters are // declared on a value, and hence are in the `FnSpace`. // // 4. Reference to a method or an associated constant: // // impl SomeStruct { // fn foo(...) // } // // Here we can have a path like // `a::b::SomeStruct::::foo::`, in which case parameters // may appear in two places. The penultimate segment, // `SomeStruct::`, contains parameters in TypeSpace, and the // final segment, `foo::` contains parameters in fn space. // // The first step then is to categorize the segments appropriately. let tcx = self.tcx(); assert!(!segments.is_empty()); let last = segments.len() - 1; let mut path_segs = vec![]; match kind { // Case 1. Reference to a struct constructor. DefKind::Ctor(CtorOf::Struct, ..) => { // Everything but the final segment should have no // parameters at all. let generics = tcx.generics_of(def_id); // Variant and struct constructors use the // generics of their parent type definition. let generics_def_id = generics.parent.unwrap_or(def_id); path_segs.push(PathSeg(generics_def_id, last)); } // Case 2. Reference to a variant constructor. DefKind::Ctor(CtorOf::Variant, ..) | DefKind::Variant => { let (generics_def_id, index) = if let Some(self_ty) = self_ty { let adt_def = self.probe_adt(span, self_ty).unwrap(); debug_assert!(adt_def.is_enum()); (adt_def.did(), last) } else if last >= 1 && segments[last - 1].args.is_some() { // Everything but the penultimate segment should have no // parameters at all. let mut def_id = def_id; // `DefKind::Ctor` -> `DefKind::Variant` if let DefKind::Ctor(..) = kind { def_id = tcx.parent(def_id); } // `DefKind::Variant` -> `DefKind::Enum` let enum_def_id = tcx.parent(def_id); (enum_def_id, last - 1) } else { // FIXME: lint here recommending `Enum::<...>::Variant` form // instead of `Enum::Variant::<...>` form. // Everything but the final segment should have no // parameters at all. let generics = tcx.generics_of(def_id); // Variant and struct constructors use the // generics of their parent type definition. (generics.parent.unwrap_or(def_id), last) }; path_segs.push(PathSeg(generics_def_id, index)); } // Case 3. Reference to a top-level value. DefKind::Fn | DefKind::Const | DefKind::ConstParam | DefKind::Static(_) => { path_segs.push(PathSeg(def_id, last)); } // Case 4. Reference to a method or associated const. DefKind::AssocFn | DefKind::AssocConst => { if segments.len() >= 2 { let generics = tcx.generics_of(def_id); path_segs.push(PathSeg(generics.parent.unwrap(), last - 1)); } path_segs.push(PathSeg(def_id, last)); } kind => bug!("unexpected definition kind {:?} for {:?}", kind, def_id), } debug!("path_segs = {:?}", path_segs); path_segs } /// Check a type `Path` and convert it to a `Ty`. pub fn res_to_ty( &self, opt_self_ty: Option>, path: &hir::Path<'_>, hir_id: hir::HirId, permit_variants: bool, ) -> Ty<'tcx> { let tcx = self.tcx(); debug!( "res_to_ty(res={:?}, opt_self_ty={:?}, path_segments={:?})", path.res, opt_self_ty, path.segments ); let span = path.span; match path.res { Res::Def(DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder, did) => { // Check for desugared `impl Trait`. assert!(tcx.is_type_alias_impl_trait(did)); let item_segment = path.segments.split_last().unwrap(); self.prohibit_generics(item_segment.1.iter(), |err| { err.note("`impl Trait` types can't have type parameters"); }); let substs = self.ast_path_substs_for_ty(span, did, item_segment.0); Ty::new_opaque(tcx, did, substs) } Res::Def( DefKind::Enum | DefKind::TyAlias | DefKind::Struct | DefKind::Union | DefKind::ForeignTy, did, ) => { assert_eq!(opt_self_ty, None); self.prohibit_generics(path.segments.split_last().unwrap().1.iter(), |_| {}); self.ast_path_to_ty(span, did, path.segments.last().unwrap()) } Res::Def(kind @ DefKind::Variant, def_id) if permit_variants => { // Convert "variant type" as if it were a real type. // The resulting `Ty` is type of the variant's enum for now. assert_eq!(opt_self_ty, None); let path_segs = self.def_ids_for_value_path_segments(path.segments, None, kind, def_id, span); let generic_segs: FxHashSet<_> = path_segs.iter().map(|PathSeg(_, index)| index).collect(); self.prohibit_generics( path.segments.iter().enumerate().filter_map(|(index, seg)| { if !generic_segs.contains(&index) { Some(seg) } else { None } }), |err| { err.note("enum variants can't have type parameters"); }, ); let PathSeg(def_id, index) = path_segs.last().unwrap(); self.ast_path_to_ty(span, *def_id, &path.segments[*index]) } Res::Def(DefKind::TyParam, def_id) => { assert_eq!(opt_self_ty, None); self.prohibit_generics(path.segments.iter(), |err| { if let Some(span) = tcx.def_ident_span(def_id) { let name = tcx.item_name(def_id); err.span_note(span, format!("type parameter `{name}` defined here")); } }); match tcx.named_bound_var(hir_id) { Some(rbv::ResolvedArg::LateBound(debruijn, index, _)) => { let name = tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local())); let br = ty::BoundTy { var: ty::BoundVar::from_u32(index), kind: ty::BoundTyKind::Param(def_id, name), }; Ty::new_bound(tcx, debruijn, br) } Some(rbv::ResolvedArg::EarlyBound(_)) => { let def_id = def_id.expect_local(); let item_def_id = tcx.hir().ty_param_owner(def_id); let generics = tcx.generics_of(item_def_id); let index = generics.param_def_id_to_index[&def_id.to_def_id()]; Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id)) } Some(rbv::ResolvedArg::Error(guar)) => Ty::new_error(tcx, guar), arg => bug!("unexpected bound var resolution for {hir_id:?}: {arg:?}"), } } Res::SelfTyParam { .. } => { // `Self` in trait or type alias. assert_eq!(opt_self_ty, None); self.prohibit_generics(path.segments.iter(), |err| { if let [hir::PathSegment { args: Some(args), ident, .. }] = &path.segments { err.span_suggestion_verbose( ident.span.shrink_to_hi().to(args.span_ext), "the `Self` type doesn't accept type parameters", "", Applicability::MaybeIncorrect, ); } }); tcx.types.self_param } Res::SelfTyAlias { alias_to: def_id, forbid_generic, .. } => { // `Self` in impl (we know the concrete type). assert_eq!(opt_self_ty, None); // Try to evaluate any array length constants. let ty = tcx.at(span).type_of(def_id).subst_identity(); let span_of_impl = tcx.span_of_impl(def_id); self.prohibit_generics(path.segments.iter(), |err| { let def_id = match *ty.kind() { ty::Adt(self_def, _) => self_def.did(), _ => return, }; let type_name = tcx.item_name(def_id); let span_of_ty = tcx.def_ident_span(def_id); let generics = tcx.generics_of(def_id).count(); let msg = format!("`Self` is of type `{ty}`"); if let (Ok(i_sp), Some(t_sp)) = (span_of_impl, span_of_ty) { let mut span: MultiSpan = vec![t_sp].into(); span.push_span_label( i_sp, format!("`Self` is on type `{type_name}` in this `impl`"), ); let mut postfix = ""; if generics == 0 { postfix = ", which doesn't have generic parameters"; } span.push_span_label( t_sp, format!("`Self` corresponds to this type{postfix}"), ); err.span_note(span, msg); } else { err.note(msg); } for segment in path.segments { if let Some(args) = segment.args && segment.ident.name == kw::SelfUpper { if generics == 0 { // FIXME(estebank): we could also verify that the arguments being // work for the `enum`, instead of just looking if it takes *any*. err.span_suggestion_verbose( segment.ident.span.shrink_to_hi().to(args.span_ext), "the `Self` type doesn't accept type parameters", "", Applicability::MachineApplicable, ); return; } else { err.span_suggestion_verbose( segment.ident.span, format!( "the `Self` type doesn't accept type parameters, use the \ concrete type's name `{type_name}` instead if you want to \ specify its type parameters" ), type_name, Applicability::MaybeIncorrect, ); } } } }); // HACK(min_const_generics): Forbid generic `Self` types // here as we can't easily do that during nameres. // // We do this before normalization as we otherwise allow // ```rust // trait AlwaysApplicable { type Assoc; } // impl AlwaysApplicable for T { type Assoc = usize; } // // trait BindsParam { // type ArrayTy; // } // impl BindsParam for ::Assoc { // type ArrayTy = [u8; Self::MAX]; // } // ``` // Note that the normalization happens in the param env of // the anon const, which is empty. This is why the // `AlwaysApplicable` impl needs a `T: ?Sized` bound for // this to compile if we were to normalize here. if forbid_generic && ty.has_param() { let mut err = tcx.sess.struct_span_err( path.span, "generic `Self` types are currently not permitted in anonymous constants", ); if let Some(hir::Node::Item(&hir::Item { kind: hir::ItemKind::Impl(impl_), .. })) = tcx.hir().get_if_local(def_id) { err.span_note(impl_.self_ty.span, "not a concrete type"); } Ty::new_error(tcx, err.emit()) } else { ty } } Res::Def(DefKind::AssocTy, def_id) => { debug_assert!(path.segments.len() >= 2); self.prohibit_generics(path.segments[..path.segments.len() - 2].iter(), |_| {}); // HACK: until we support ``, assume all of them are. let constness = if tcx.has_attr(tcx.parent(def_id), sym::const_trait) { ty::BoundConstness::ConstIfConst } else { ty::BoundConstness::NotConst }; self.qpath_to_ty( span, opt_self_ty, def_id, &path.segments[path.segments.len() - 2], path.segments.last().unwrap(), constness, ) } Res::PrimTy(prim_ty) => { assert_eq!(opt_self_ty, None); self.prohibit_generics(path.segments.iter(), |err| { let name = prim_ty.name_str(); for segment in path.segments { if let Some(args) = segment.args { err.span_suggestion_verbose( segment.ident.span.shrink_to_hi().to(args.span_ext), format!("primitive type `{name}` doesn't have generic parameters"), "", Applicability::MaybeIncorrect, ); } } }); match prim_ty { hir::PrimTy::Bool => tcx.types.bool, hir::PrimTy::Char => tcx.types.char, hir::PrimTy::Int(it) => Ty::new_int(tcx, ty::int_ty(it)), hir::PrimTy::Uint(uit) => Ty::new_uint(tcx, ty::uint_ty(uit)), hir::PrimTy::Float(ft) => Ty::new_float(tcx, ty::float_ty(ft)), hir::PrimTy::Str => tcx.types.str_, } } Res::Err => { let e = self .tcx() .sess .delay_span_bug(path.span, "path with `Res::Err` but no error emitted"); self.set_tainted_by_errors(e); Ty::new_error(self.tcx(), e) } _ => span_bug!(span, "unexpected resolution: {:?}", path.res), } } /// Parses the programmer's textual representation of a type into our /// internal notion of a type. pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> { self.ast_ty_to_ty_inner(ast_ty, false, false) } /// Parses the programmer's textual representation of a type into our /// internal notion of a type. This is meant to be used within a path. pub fn ast_ty_to_ty_in_path(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> { self.ast_ty_to_ty_inner(ast_ty, false, true) } /// Turns a `hir::Ty` into a `Ty`. For diagnostics' purposes we keep track of whether trait /// objects are borrowed like `&dyn Trait` to avoid emitting redundant errors. #[instrument(level = "debug", skip(self), ret)] fn ast_ty_to_ty_inner(&self, ast_ty: &hir::Ty<'_>, borrowed: bool, in_path: bool) -> Ty<'tcx> { let tcx = self.tcx(); let result_ty = match &ast_ty.kind { hir::TyKind::Slice(ty) => Ty::new_slice(tcx, self.ast_ty_to_ty(ty)), hir::TyKind::Ptr(mt) => { Ty::new_ptr(tcx, ty::TypeAndMut { ty: self.ast_ty_to_ty(mt.ty), mutbl: mt.mutbl }) } hir::TyKind::Ref(region, mt) => { let r = self.ast_region_to_region(region, None); debug!(?r); let t = self.ast_ty_to_ty_inner(mt.ty, true, false); Ty::new_ref(tcx, r, ty::TypeAndMut { ty: t, mutbl: mt.mutbl }) } hir::TyKind::Never => tcx.types.never, hir::TyKind::Tup(fields) => { Ty::new_tup_from_iter(tcx, fields.iter().map(|t| self.ast_ty_to_ty(t))) } hir::TyKind::BareFn(bf) => { require_c_abi_if_c_variadic(tcx, bf.decl, bf.abi, ast_ty.span); Ty::new_fn_ptr( tcx, self.ty_of_fn(ast_ty.hir_id, bf.unsafety, bf.abi, bf.decl, None, Some(ast_ty)), ) } hir::TyKind::TraitObject(bounds, lifetime, repr) => { self.maybe_lint_bare_trait(ast_ty, in_path); let repr = match repr { TraitObjectSyntax::Dyn | TraitObjectSyntax::None => ty::Dyn, TraitObjectSyntax::DynStar => ty::DynStar, }; self.conv_object_ty_poly_trait_ref( ast_ty.span, ast_ty.hir_id, bounds, lifetime, borrowed, repr, ) } hir::TyKind::Path(hir::QPath::Resolved(maybe_qself, path)) => { debug!(?maybe_qself, ?path); let opt_self_ty = maybe_qself.as_ref().map(|qself| self.ast_ty_to_ty(qself)); self.res_to_ty(opt_self_ty, path, ast_ty.hir_id, false) } &hir::TyKind::OpaqueDef(item_id, lifetimes, in_trait) => { let opaque_ty = tcx.hir().item(item_id); match opaque_ty.kind { hir::ItemKind::OpaqueTy(&hir::OpaqueTy { origin, .. }) => { let local_def_id = item_id.owner_id.def_id; // If this is an RPITIT and we are using the new RPITIT lowering scheme, we // generate the def_id of an associated type for the trait and return as // type a projection. let def_id = if in_trait && tcx.lower_impl_trait_in_trait_to_assoc_ty() { tcx.associated_type_for_impl_trait_in_trait(local_def_id).to_def_id() } else { local_def_id.to_def_id() }; self.impl_trait_ty_to_ty(def_id, lifetimes, origin, in_trait) } ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i), } } hir::TyKind::Path(hir::QPath::TypeRelative(qself, segment)) => { debug!(?qself, ?segment); let ty = self.ast_ty_to_ty_inner(qself, false, true); self.associated_path_to_ty(ast_ty.hir_id, ast_ty.span, ty, qself, segment, false) .map(|(ty, _, _)| ty) .unwrap_or_else(|guar| Ty::new_error(tcx, guar)) } &hir::TyKind::Path(hir::QPath::LangItem(lang_item, span, _)) => { let def_id = tcx.require_lang_item(lang_item, Some(span)); let (substs, _) = self.create_substs_for_ast_path( span, def_id, &[], &hir::PathSegment::invalid(), &GenericArgs::none(), true, None, ty::BoundConstness::NotConst, ); tcx.at(span).type_of(def_id).subst(tcx, substs) } hir::TyKind::Array(ty, length) => { let length = match length { &hir::ArrayLen::Infer(_, span) => self.ct_infer(tcx.types.usize, None, span), hir::ArrayLen::Body(constant) => { ty::Const::from_anon_const(tcx, constant.def_id) } }; Ty::new_array_with_const_len(tcx, self.ast_ty_to_ty(ty), length) } hir::TyKind::Typeof(e) => { let ty_erased = tcx.type_of(e.def_id).subst_identity(); let ty = tcx.fold_regions(ty_erased, |r, _| { if r.is_erased() { tcx.lifetimes.re_static } else { r } }); let span = ast_ty.span; let (ty, opt_sugg) = if let Some(ty) = ty.make_suggestable(tcx, false) { (ty, Some((span, Applicability::MachineApplicable))) } else { (ty, None) }; tcx.sess.emit_err(TypeofReservedKeywordUsed { span, ty, opt_sugg }); ty } hir::TyKind::Infer => { // Infer also appears as the type of arguments or return // values in an ExprKind::Closure, or as // the type of local variables. Both of these cases are // handled specially and will not descend into this routine. self.ty_infer(None, ast_ty.span) } hir::TyKind::Err(guar) => Ty::new_error(tcx, *guar), }; self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span); result_ty } #[instrument(level = "debug", skip(self), ret)] fn impl_trait_ty_to_ty( &self, def_id: DefId, lifetimes: &[hir::GenericArg<'_>], origin: OpaqueTyOrigin, in_trait: bool, ) -> Ty<'tcx> { debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes); let tcx = self.tcx(); let generics = tcx.generics_of(def_id); debug!("impl_trait_ty_to_ty: generics={:?}", generics); let substs = InternalSubsts::for_item(tcx, def_id, |param, _| { // We use `generics.count() - lifetimes.len()` here instead of `generics.parent_count` // since return-position impl trait in trait squashes all of the generics from its source fn // into its own generics, so the opaque's "own" params isn't always just lifetimes. if let Some(i) = (param.index as usize).checked_sub(generics.count() - lifetimes.len()) { // Resolve our own lifetime parameters. let GenericParamDefKind::Lifetime { .. } = param.kind else { bug!() }; let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] else { bug!() }; self.ast_region_to_region(lifetime, None).into() } else { tcx.mk_param_from_def(param) } }); debug!("impl_trait_ty_to_ty: substs={:?}", substs); if in_trait { Ty::new_projection(tcx, def_id, substs) } else { Ty::new_opaque(tcx, def_id, substs) } } pub fn ty_of_arg(&self, ty: &hir::Ty<'_>, expected_ty: Option>) -> Ty<'tcx> { match ty.kind { hir::TyKind::Infer if expected_ty.is_some() => { self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span); expected_ty.unwrap() } _ => self.ast_ty_to_ty(ty), } } #[instrument(level = "debug", skip(self, hir_id, unsafety, abi, decl, generics, hir_ty), ret)] pub fn ty_of_fn( &self, hir_id: hir::HirId, unsafety: hir::Unsafety, abi: abi::Abi, decl: &hir::FnDecl<'_>, generics: Option<&hir::Generics<'_>>, hir_ty: Option<&hir::Ty<'_>>, ) -> ty::PolyFnSig<'tcx> { let tcx = self.tcx(); let bound_vars = tcx.late_bound_vars(hir_id); debug!(?bound_vars); // We proactively collect all the inferred type params to emit a single error per fn def. let mut visitor = HirPlaceholderCollector::default(); let mut infer_replacements = vec![]; if let Some(generics) = generics { walk_generics(&mut visitor, generics); } let input_tys: Vec<_> = decl .inputs .iter() .enumerate() .map(|(i, a)| { if let hir::TyKind::Infer = a.kind && !self.allow_ty_infer() { if let Some(suggested_ty) = self.suggest_trait_fn_ty_for_impl_fn_infer(hir_id, Some(i)) { infer_replacements.push((a.span, suggested_ty.to_string())); return suggested_ty; } } // Only visit the type looking for `_` if we didn't fix the type above visitor.visit_ty(a); self.ty_of_arg(a, None) }) .collect(); let output_ty = match decl.output { hir::FnRetTy::Return(output) => { if let hir::TyKind::Infer = output.kind && !self.allow_ty_infer() && let Some(suggested_ty) = self.suggest_trait_fn_ty_for_impl_fn_infer(hir_id, None) { infer_replacements.push((output.span, suggested_ty.to_string())); suggested_ty } else { visitor.visit_ty(output); self.ast_ty_to_ty(output) } } hir::FnRetTy::DefaultReturn(..) => Ty::new_unit(tcx,), }; debug!(?output_ty); let fn_ty = tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi); let bare_fn_ty = ty::Binder::bind_with_vars(fn_ty, bound_vars); if !self.allow_ty_infer() && !(visitor.0.is_empty() && infer_replacements.is_empty()) { // We always collect the spans for placeholder types when evaluating `fn`s, but we // only want to emit an error complaining about them if infer types (`_`) are not // allowed. `allow_ty_infer` gates this behavior. We check for the presence of // `ident_span` to not emit an error twice when we have `fn foo(_: fn() -> _)`. let mut diag = crate::collect::placeholder_type_error_diag( tcx, generics, visitor.0, infer_replacements.iter().map(|(s, _)| *s).collect(), true, hir_ty, "function", ); if !infer_replacements.is_empty() { diag.multipart_suggestion( format!( "try replacing `_` with the type{} in the corresponding trait method signature", rustc_errors::pluralize!(infer_replacements.len()), ), infer_replacements, Applicability::MachineApplicable, ); } diag.emit(); } // Find any late-bound regions declared in return type that do // not appear in the arguments. These are not well-formed. // // Example: // for<'a> fn() -> &'a str <-- 'a is bad // for<'a> fn(&'a String) -> &'a str <-- 'a is ok let inputs = bare_fn_ty.inputs(); let late_bound_in_args = tcx.collect_constrained_late_bound_regions(&inputs.map_bound(|i| i.to_owned())); let output = bare_fn_ty.output(); let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output); self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| { struct_span_err!( tcx.sess, decl.output.span(), E0581, "return type references {}, which is not constrained by the fn input types", br_name ) }); bare_fn_ty } /// Given a fn_hir_id for a impl function, suggest the type that is found on the /// corresponding function in the trait that the impl implements, if it exists. /// If arg_idx is Some, then it corresponds to an input type index, otherwise it /// corresponds to the return type. fn suggest_trait_fn_ty_for_impl_fn_infer( &self, fn_hir_id: hir::HirId, arg_idx: Option, ) -> Option> { let tcx = self.tcx(); let hir = tcx.hir(); let hir::Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), ident, .. }) = hir.get(fn_hir_id) else { return None }; let i = hir.get_parent(fn_hir_id).expect_item().expect_impl(); let trait_ref = self.instantiate_mono_trait_ref( i.of_trait.as_ref()?, self.ast_ty_to_ty(i.self_ty), ty::BoundConstness::NotConst, ); let assoc = tcx.associated_items(trait_ref.def_id).find_by_name_and_kind( tcx, *ident, ty::AssocKind::Fn, trait_ref.def_id, )?; let fn_sig = tcx.fn_sig(assoc.def_id).subst( tcx, trait_ref.substs.extend_to(tcx, assoc.def_id, |param, _| tcx.mk_param_from_def(param)), ); let fn_sig = tcx.liberate_late_bound_regions(fn_hir_id.expect_owner().to_def_id(), fn_sig); Some(if let Some(arg_idx) = arg_idx { *fn_sig.inputs().get(arg_idx)? } else { fn_sig.output() }) } #[instrument(level = "trace", skip(self, generate_err))] fn validate_late_bound_regions( &self, constrained_regions: FxHashSet, referenced_regions: FxHashSet, generate_err: impl Fn(&str) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>, ) { for br in referenced_regions.difference(&constrained_regions) { let br_name = match *br { ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon(..) | ty::BrEnv => { "an anonymous lifetime".to_string() } ty::BrNamed(_, name) => format!("lifetime `{}`", name), }; let mut err = generate_err(&br_name); if let ty::BrNamed(_, kw::UnderscoreLifetime) | ty::BrAnon(..) = *br { // The only way for an anonymous lifetime to wind up // in the return type but **also** be unconstrained is // if it only appears in "associated types" in the // input. See #47511 and #62200 for examples. In this case, // though we can easily give a hint that ought to be // relevant. err.note( "lifetimes appearing in an associated or opaque type are not considered constrained", ); err.note("consider introducing a named lifetime parameter"); } err.emit(); } } /// Given the bounds on an object, determines what single region bound (if any) we can /// use to summarize this type. The basic idea is that we will use the bound the user /// provided, if they provided one, and otherwise search the supertypes of trait bounds /// for region bounds. It may be that we can derive no bound at all, in which case /// we return `None`. fn compute_object_lifetime_bound( &self, span: Span, existential_predicates: &'tcx ty::List>, ) -> Option> // if None, use the default { let tcx = self.tcx(); debug!("compute_opt_region_bound(existential_predicates={:?})", existential_predicates); // No explicit region bound specified. Therefore, examine trait // bounds and see if we can derive region bounds from those. let derived_region_bounds = object_region_bounds(tcx, existential_predicates); // If there are no derived region bounds, then report back that we // can find no region bound. The caller will use the default. if derived_region_bounds.is_empty() { return None; } // If any of the derived region bounds are 'static, that is always // the best choice. if derived_region_bounds.iter().any(|r| r.is_static()) { return Some(tcx.lifetimes.re_static); } // Determine whether there is exactly one unique region in the set // of derived region bounds. If so, use that. Otherwise, report an // error. let r = derived_region_bounds[0]; if derived_region_bounds[1..].iter().any(|r1| r != *r1) { tcx.sess.emit_err(AmbiguousLifetimeBound { span }); } Some(r) } }