//! "Collection" is the process of determining the type and other external //! details of each item in Rust. Collection is specifically concerned //! with *inter-procedural* things -- for example, for a function //! definition, collection will figure out the type and signature of the //! function, but it will not visit the *body* of the function in any way, //! nor examine type annotations on local variables (that's the job of //! type *checking*). //! //! Collecting is ultimately defined by a bundle of queries that //! inquire after various facts about the items in the crate (e.g., //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function //! for the full set. //! //! At present, however, we do run collection across all items in the //! crate as a kind of pass. This should eventually be factored away. use rustc_ast::Recovered; use rustc_data_structures::captures::Captures; use rustc_data_structures::fx::{FxHashSet, FxIndexMap}; use rustc_data_structures::unord::UnordMap; use rustc_errors::{struct_span_code_err, Applicability, Diag, ErrorGuaranteed, StashKey, E0228}; use rustc_hir::def::DefKind; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::{self, walk_generics, Visitor}; use rustc_hir::{self as hir}; use rustc_hir::{GenericParamKind, Node}; use rustc_infer::infer::{InferCtxt, TyCtxtInferExt}; use rustc_infer::traits::ObligationCause; use rustc_middle::hir::nested_filter; use rustc_middle::query::Providers; use rustc_middle::ty::util::{Discr, IntTypeExt}; use rustc_middle::ty::{self, AdtKind, Const, IsSuggestable, Ty, TyCtxt, Upcast}; use rustc_middle::{bug, span_bug}; use rustc_span::symbol::{kw, sym, Ident, Symbol}; use rustc_span::{Span, DUMMY_SP}; use rustc_target::abi::FieldIdx; use rustc_target::spec::abi; use rustc_trait_selection::infer::InferCtxtExt; use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName; use rustc_trait_selection::traits::ObligationCtxt; use std::cell::Cell; use std::iter; use std::ops::Bound; use crate::check::intrinsic::intrinsic_operation_unsafety; use crate::errors; use crate::hir_ty_lowering::{HirTyLowerer, RegionInferReason}; pub use type_of::test_opaque_hidden_types; mod generics_of; mod item_bounds; mod predicates_of; mod resolve_bound_vars; mod type_of; /////////////////////////////////////////////////////////////////////////// pub fn provide(providers: &mut Providers) { resolve_bound_vars::provide(providers); *providers = Providers { type_of: type_of::type_of, type_of_opaque: type_of::type_of_opaque, type_alias_is_lazy: type_of::type_alias_is_lazy, item_bounds: item_bounds::item_bounds, explicit_item_bounds: item_bounds::explicit_item_bounds, item_super_predicates: item_bounds::item_super_predicates, explicit_item_super_predicates: item_bounds::explicit_item_super_predicates, item_non_self_assumptions: item_bounds::item_non_self_assumptions, generics_of: generics_of::generics_of, predicates_of: predicates_of::predicates_of, predicates_defined_on, explicit_predicates_of: predicates_of::explicit_predicates_of, super_predicates_of: predicates_of::super_predicates_of, implied_predicates_of: predicates_of::implied_predicates_of, super_predicates_that_define_assoc_item: predicates_of::super_predicates_that_define_assoc_item, trait_explicit_predicates_and_bounds: predicates_of::trait_explicit_predicates_and_bounds, type_param_predicates: predicates_of::type_param_predicates, trait_def, adt_def, fn_sig, impl_trait_header, coroutine_kind, coroutine_for_closure, is_type_alias_impl_trait, find_field, ..*providers }; } /////////////////////////////////////////////////////////////////////////// /// Context specific to some particular item. This is what implements [`HirTyLowerer`]. /// /// # `ItemCtxt` vs `FnCtxt` /// /// `ItemCtxt` is primarily used to type-check item signatures and lower them /// from HIR to their [`ty::Ty`] representation, which is exposed using [`HirTyLowerer`]. /// It's also used for the bodies of items like structs where the body (the fields) /// are just signatures. /// /// This is in contrast to `FnCtxt`, which is used to type-check bodies of /// functions, closures, and `const`s -- anywhere that expressions and statements show up. /// /// An important thing to note is that `ItemCtxt` does no inference -- it has no [`InferCtxt`] -- /// while `FnCtxt` does do inference. /// /// [`InferCtxt`]: rustc_infer::infer::InferCtxt /// /// # Trait predicates /// /// `ItemCtxt` has information about the predicates that are defined /// on the trait. Unfortunately, this predicate information is /// available in various different forms at various points in the /// process. So we can't just store a pointer to e.g., the HIR or the /// parsed ty form, we have to be more flexible. To this end, the /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy /// `probe_ty_param_bounds` requests, drawing the information from /// the HIR (`hir::Generics`), recursively. pub struct ItemCtxt<'tcx> { tcx: TyCtxt<'tcx>, item_def_id: LocalDefId, tainted_by_errors: Cell>, } /////////////////////////////////////////////////////////////////////////// #[derive(Default)] pub(crate) struct HirPlaceholderCollector(pub(crate) Vec); impl<'v> Visitor<'v> for HirPlaceholderCollector { fn visit_ty(&mut self, t: &'v hir::Ty<'v>) { if let hir::TyKind::Infer = t.kind { self.0.push(t.span); } intravisit::walk_ty(self, t) } fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) { match generic_arg { hir::GenericArg::Infer(inf) => { self.0.push(inf.span); intravisit::walk_inf(self, inf); } hir::GenericArg::Type(t) => self.visit_ty(t), _ => {} } } fn visit_array_length(&mut self, length: &'v hir::ArrayLen<'v>) { if let hir::ArrayLen::Infer(inf) = length { self.0.push(inf.span); } intravisit::walk_array_len(self, length) } } pub struct CollectItemTypesVisitor<'tcx> { pub tcx: TyCtxt<'tcx>, } /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed /// and suggest adding type parameters in the appropriate place, taking into consideration any and /// all already existing generic type parameters to avoid suggesting a name that is already in use. pub(crate) fn placeholder_type_error<'tcx>( tcx: TyCtxt<'tcx>, generics: Option<&hir::Generics<'_>>, placeholder_types: Vec, suggest: bool, hir_ty: Option<&hir::Ty<'_>>, kind: &'static str, ) { if placeholder_types.is_empty() { return; } placeholder_type_error_diag(tcx, generics, placeholder_types, vec![], suggest, hir_ty, kind) .emit(); } pub(crate) fn placeholder_type_error_diag<'tcx>( tcx: TyCtxt<'tcx>, generics: Option<&hir::Generics<'_>>, placeholder_types: Vec, additional_spans: Vec, suggest: bool, hir_ty: Option<&hir::Ty<'_>>, kind: &'static str, ) -> Diag<'tcx> { if placeholder_types.is_empty() { return bad_placeholder(tcx, additional_spans, kind); } let params = generics.map(|g| g.params).unwrap_or_default(); let type_name = params.next_type_param_name(None); let mut sugg: Vec<_> = placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect(); if let Some(generics) = generics { if let Some(arg) = params.iter().find(|arg| { matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. })) }) { // Account for `_` already present in cases like `struct S<_>(_);` and suggest // `struct S(T);` instead of `struct S<_, T>(T);`. sugg.push((arg.span, (*type_name).to_string())); } else if let Some(span) = generics.span_for_param_suggestion() { // Account for bounds, we want `fn foo(_: K)` not `fn foo(_: K)`. sugg.push((span, format!(", {type_name}"))); } else { sugg.push((generics.span, format!("<{type_name}>"))); } } let mut err = bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind); // Suggest, but only if it is not a function in const or static if suggest { let mut is_fn = false; let mut is_const_or_static = false; if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind { is_fn = true; // Check if parent is const or static is_const_or_static = matches!( tcx.parent_hir_node(hir_ty.hir_id), Node::Item(&hir::Item { kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..), .. }) | Node::TraitItem(&hir::TraitItem { kind: hir::TraitItemKind::Const(..), .. }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. }) ); } // if function is wrapped around a const or static, // then don't show the suggestion if !(is_fn && is_const_or_static) { err.multipart_suggestion( "use type parameters instead", sugg, Applicability::HasPlaceholders, ); } } err } fn reject_placeholder_type_signatures_in_item<'tcx>( tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>, ) { let (generics, suggest) = match &item.kind { hir::ItemKind::Union(_, generics) | hir::ItemKind::Enum(_, generics) | hir::ItemKind::TraitAlias(generics, _) | hir::ItemKind::Trait(_, _, generics, ..) | hir::ItemKind::Impl(hir::Impl { generics, .. }) | hir::ItemKind::Struct(_, generics) => (generics, true), hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. }) | hir::ItemKind::TyAlias(_, generics) => (generics, false), // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type. _ => return, }; let mut visitor = HirPlaceholderCollector::default(); visitor.visit_item(item); placeholder_type_error(tcx, Some(generics), visitor.0, suggest, None, item.kind.descr()); } impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> { type NestedFilter = nested_filter::OnlyBodies; fn nested_visit_map(&mut self) -> Self::Map { self.tcx.hir() } fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) { lower_item(self.tcx, item.item_id()); reject_placeholder_type_signatures_in_item(self.tcx, item); intravisit::walk_item(self, item); } fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) { for param in generics.params { match param.kind { hir::GenericParamKind::Lifetime { .. } => {} hir::GenericParamKind::Type { default: Some(_), .. } => { self.tcx.ensure().type_of(param.def_id); } hir::GenericParamKind::Type { .. } => {} hir::GenericParamKind::Const { default, .. } => { self.tcx.ensure().type_of(param.def_id); if let Some(default) = default { // need to store default and type of default self.tcx.ensure().type_of(default.def_id); self.tcx.ensure().const_param_default(param.def_id); } } } } intravisit::walk_generics(self, generics); } fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) { if let hir::ExprKind::Closure(closure) = expr.kind { self.tcx.ensure().generics_of(closure.def_id); self.tcx.ensure().codegen_fn_attrs(closure.def_id); // We do not call `type_of` for closures here as that // depends on typecheck and would therefore hide // any further errors in case one typeck fails. } intravisit::walk_expr(self, expr); } fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) { lower_trait_item(self.tcx, trait_item.trait_item_id()); intravisit::walk_trait_item(self, trait_item); } fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) { lower_impl_item(self.tcx, impl_item.impl_item_id()); intravisit::walk_impl_item(self, impl_item); } } /////////////////////////////////////////////////////////////////////////// // Utility types and common code for the above passes. fn bad_placeholder<'tcx>( tcx: TyCtxt<'tcx>, mut spans: Vec, kind: &'static str, ) -> Diag<'tcx> { let kind = if kind.ends_with('s') { format!("{kind}es") } else { format!("{kind}s") }; spans.sort(); tcx.dcx().create_err(errors::PlaceholderNotAllowedItemSignatures { spans, kind }) } impl<'tcx> ItemCtxt<'tcx> { pub fn new(tcx: TyCtxt<'tcx>, item_def_id: LocalDefId) -> ItemCtxt<'tcx> { ItemCtxt { tcx, item_def_id, tainted_by_errors: Cell::new(None) } } pub fn lower_ty(&self, hir_ty: &hir::Ty<'tcx>) -> Ty<'tcx> { self.lowerer().lower_ty(hir_ty) } pub fn hir_id(&self) -> hir::HirId { self.tcx.local_def_id_to_hir_id(self.item_def_id) } pub fn node(&self) -> hir::Node<'tcx> { self.tcx.hir_node(self.hir_id()) } fn check_tainted_by_errors(&self) -> Result<(), ErrorGuaranteed> { match self.tainted_by_errors.get() { Some(err) => Err(err), None => Ok(()), } } } impl<'tcx> HirTyLowerer<'tcx> for ItemCtxt<'tcx> { fn tcx(&self) -> TyCtxt<'tcx> { self.tcx } fn item_def_id(&self) -> LocalDefId { self.item_def_id } fn re_infer(&self, span: Span, reason: RegionInferReason<'_>) -> ty::Region<'tcx> { if let RegionInferReason::BorrowedObjectLifetimeDefault = reason { let e = struct_span_code_err!( self.tcx().dcx(), span, E0228, "the lifetime bound for this object type cannot be deduced \ from context; please supply an explicit bound" ) .emit(); self.set_tainted_by_errors(e); ty::Region::new_error(self.tcx(), e) } else { // This indicates an illegal lifetime in a non-assoc-trait position ty::Region::new_error_with_message(self.tcx(), span, "unelided lifetime in signature") } } fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> { Ty::new_error_with_message(self.tcx(), span, "bad placeholder type") } fn ct_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> { ty::Const::new_error_with_message(self.tcx(), span, "bad placeholder constant") } fn probe_ty_param_bounds( &self, span: Span, def_id: LocalDefId, assoc_name: Ident, ) -> ty::GenericPredicates<'tcx> { self.tcx.at(span).type_param_predicates((self.item_def_id, def_id, assoc_name)) } fn lower_assoc_ty( &self, span: Span, item_def_id: DefId, item_segment: &hir::PathSegment<'tcx>, poly_trait_ref: ty::PolyTraitRef<'tcx>, ) -> Ty<'tcx> { if let Some(trait_ref) = poly_trait_ref.no_bound_vars() { let item_args = self.lowerer().lower_generic_args_of_assoc_item( span, item_def_id, item_segment, trait_ref.args, ); Ty::new_projection(self.tcx(), item_def_id, item_args) } else { // There are no late-bound regions; we can just ignore the binder. let (mut mpart_sugg, mut inferred_sugg) = (None, None); let mut bound = String::new(); match self.node() { hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => { let item = self .tcx .hir() .expect_item(self.tcx.hir().get_parent_item(self.hir_id()).def_id); match &item.kind { hir::ItemKind::Enum(_, generics) | hir::ItemKind::Struct(_, generics) | hir::ItemKind::Union(_, generics) => { let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics); let (lt_sp, sugg) = match generics.params { [] => (generics.span, format!("<{lt_name}>")), [bound, ..] => (bound.span.shrink_to_lo(), format!("{lt_name}, ")), }; mpart_sugg = Some(errors::AssociatedTypeTraitUninferredGenericParamsMultipartSuggestion { fspan: lt_sp, first: sugg, sspan: span.with_hi(item_segment.ident.span.lo()), second: format!( "{}::", // Replace the existing lifetimes with a new named lifetime. self.tcx.instantiate_bound_regions_uncached( poly_trait_ref, |_| { ty::Region::new_early_param(self.tcx, ty::EarlyParamRegion { index: 0, name: Symbol::intern(<_name), }) } ), ), }); } _ => {} } } hir::Node::Item(hir::Item { kind: hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..), .. }) => {} hir::Node::Item(_) | hir::Node::ForeignItem(_) | hir::Node::TraitItem(_) | hir::Node::ImplItem(_) => { inferred_sugg = Some(span.with_hi(item_segment.ident.span.lo())); bound = format!( "{}::", // Erase named lt, we want `::C`, not `::C`. self.tcx.anonymize_bound_vars(poly_trait_ref).skip_binder(), ); } _ => {} } Ty::new_error( self.tcx(), self.tcx().dcx().emit_err(errors::AssociatedTypeTraitUninferredGenericParams { span, inferred_sugg, bound, mpart_sugg, }), ) } } fn probe_adt(&self, _span: Span, ty: Ty<'tcx>) -> Option> { // FIXME(#103640): Should we handle the case where `ty` is a projection? ty.ty_adt_def() } fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) { // There's no place to record types from signatures? } fn infcx(&self) -> Option<&InferCtxt<'tcx>> { None } fn set_tainted_by_errors(&self, err: ErrorGuaranteed) { self.tainted_by_errors.set(Some(err)); } fn lower_fn_sig( &self, decl: &hir::FnDecl<'tcx>, generics: Option<&hir::Generics<'_>>, hir_id: rustc_hir::HirId, hir_ty: Option<&hir::Ty<'_>>, ) -> (Vec>, Ty<'tcx>) { let tcx = self.tcx(); // 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 = decl .inputs .iter() .enumerate() .map(|(i, a)| { if let hir::TyKind::Infer = a.kind { if let Some(suggested_ty) = self.lowerer().suggest_trait_fn_ty_for_impl_fn_infer(hir_id, Some(i)) { infer_replacements.push((a.span, suggested_ty.to_string())); return Ty::new_error_with_message(tcx, a.span, suggested_ty.to_string()); } } // Only visit the type looking for `_` if we didn't fix the type above visitor.visit_ty(a); self.lowerer().lower_arg_ty(a, None) }) .collect(); let output_ty = match decl.output { hir::FnRetTy::Return(output) => { if let hir::TyKind::Infer = output.kind && let Some(suggested_ty) = self.lowerer().suggest_trait_fn_ty_for_impl_fn_infer(hir_id, None) { infer_replacements.push((output.span, suggested_ty.to_string())); Ty::new_error_with_message(tcx, output.span, suggested_ty.to_string()) } else { visitor.visit_ty(output); self.lower_ty(output) } } hir::FnRetTy::DefaultReturn(..) => tcx.types.unit, }; if !(visitor.0.is_empty() && infer_replacements.is_empty()) { // 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, ); } self.set_tainted_by_errors(diag.emit()); } (input_tys, output_ty) } } /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present. fn get_new_lifetime_name<'tcx>( tcx: TyCtxt<'tcx>, poly_trait_ref: ty::PolyTraitRef<'tcx>, generics: &hir::Generics<'tcx>, ) -> String { let existing_lifetimes = tcx .collect_referenced_late_bound_regions(poly_trait_ref) .into_iter() .filter_map(|lt| { if let ty::BoundRegionKind::BrNamed(_, name) = lt { Some(name.as_str().to_string()) } else { None } }) .chain(generics.params.iter().filter_map(|param| { if let hir::GenericParamKind::Lifetime { .. } = ¶m.kind { Some(param.name.ident().as_str().to_string()) } else { None } })) .collect::>(); let a_to_z_repeat_n = |n| { (b'a'..=b'z').map(move |c| { let mut s = '\''.to_string(); s.extend(std::iter::repeat(char::from(c)).take(n)); s }) }; // If all single char lifetime names are present, we wrap around and double the chars. (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap() } #[instrument(level = "debug", skip_all)] fn lower_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) { let it = tcx.hir().item(item_id); debug!(item = %it.ident, id = %it.hir_id()); let def_id = item_id.owner_id.def_id; match &it.kind { // These don't define types. hir::ItemKind::ExternCrate(_) | hir::ItemKind::Use(..) | hir::ItemKind::Macro(..) | hir::ItemKind::Mod(_) | hir::ItemKind::GlobalAsm(_) => {} hir::ItemKind::ForeignMod { items, .. } => { for item in *items { let item = tcx.hir().foreign_item(item.id); tcx.ensure().generics_of(item.owner_id); tcx.ensure().type_of(item.owner_id); tcx.ensure().predicates_of(item.owner_id); match item.kind { hir::ForeignItemKind::Fn(..) => { tcx.ensure().codegen_fn_attrs(item.owner_id); tcx.ensure().fn_sig(item.owner_id) } hir::ForeignItemKind::Static(..) => { tcx.ensure().codegen_fn_attrs(item.owner_id); let mut visitor = HirPlaceholderCollector::default(); visitor.visit_foreign_item(item); placeholder_type_error( tcx, None, visitor.0, false, None, "static variable", ); } _ => (), } } } hir::ItemKind::Enum(..) => { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); lower_enum_variant_types(tcx, def_id.to_def_id()); } hir::ItemKind::Impl { .. } => { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().impl_trait_header(def_id); tcx.ensure().predicates_of(def_id); tcx.ensure().associated_items(def_id); } hir::ItemKind::Trait(..) => { tcx.ensure().generics_of(def_id); tcx.ensure().trait_def(def_id); tcx.at(it.span).super_predicates_of(def_id); tcx.ensure().predicates_of(def_id); tcx.ensure().associated_items(def_id); } hir::ItemKind::TraitAlias(..) => { tcx.ensure().generics_of(def_id); tcx.at(it.span).implied_predicates_of(def_id); tcx.at(it.span).super_predicates_of(def_id); tcx.ensure().predicates_of(def_id); } hir::ItemKind::Struct(struct_def, _) | hir::ItemKind::Union(struct_def, _) => { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); for f in struct_def.fields() { tcx.ensure().generics_of(f.def_id); tcx.ensure().type_of(f.def_id); tcx.ensure().predicates_of(f.def_id); } if let Some(ctor_def_id) = struct_def.ctor_def_id() { lower_variant_ctor(tcx, ctor_def_id); } } // Don't call `type_of` on opaque types, since that depends on type // checking function bodies. `check_item_type` ensures that it's called // instead. hir::ItemKind::OpaqueTy(..) => { tcx.ensure().generics_of(def_id); tcx.ensure().predicates_of(def_id); tcx.ensure().explicit_item_bounds(def_id); tcx.ensure().explicit_item_super_predicates(def_id); tcx.ensure().item_bounds(def_id); tcx.ensure().item_super_predicates(def_id); } hir::ItemKind::TyAlias(..) => { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); } hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..) => { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); if !ty.is_suggestable_infer_ty() { let mut visitor = HirPlaceholderCollector::default(); visitor.visit_item(it); placeholder_type_error(tcx, None, visitor.0, false, None, it.kind.descr()); } } hir::ItemKind::Fn(..) => { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); tcx.ensure().fn_sig(def_id); tcx.ensure().codegen_fn_attrs(def_id); } } } fn lower_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) { let trait_item = tcx.hir().trait_item(trait_item_id); let def_id = trait_item_id.owner_id; tcx.ensure().generics_of(def_id); match trait_item.kind { hir::TraitItemKind::Fn(..) => { tcx.ensure().codegen_fn_attrs(def_id); tcx.ensure().type_of(def_id); tcx.ensure().fn_sig(def_id); } hir::TraitItemKind::Const(ty, body_id) => { tcx.ensure().type_of(def_id); if !tcx.dcx().has_stashed_diagnostic(ty.span, StashKey::ItemNoType) && !(ty.is_suggestable_infer_ty() && body_id.is_some()) { // Account for `const C: _;`. let mut visitor = HirPlaceholderCollector::default(); visitor.visit_trait_item(trait_item); placeholder_type_error(tcx, None, visitor.0, false, None, "associated constant"); } } hir::TraitItemKind::Type(_, Some(_)) => { tcx.ensure().item_bounds(def_id); tcx.ensure().item_super_predicates(def_id); tcx.ensure().type_of(def_id); // Account for `type T = _;`. let mut visitor = HirPlaceholderCollector::default(); visitor.visit_trait_item(trait_item); placeholder_type_error(tcx, None, visitor.0, false, None, "associated type"); } hir::TraitItemKind::Type(_, None) => { tcx.ensure().item_bounds(def_id); tcx.ensure().item_super_predicates(def_id); // #74612: Visit and try to find bad placeholders // even if there is no concrete type. let mut visitor = HirPlaceholderCollector::default(); visitor.visit_trait_item(trait_item); placeholder_type_error(tcx, None, visitor.0, false, None, "associated type"); } }; tcx.ensure().predicates_of(def_id); } fn lower_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) { let def_id = impl_item_id.owner_id; tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); let impl_item = tcx.hir().impl_item(impl_item_id); match impl_item.kind { hir::ImplItemKind::Fn(..) => { tcx.ensure().codegen_fn_attrs(def_id); tcx.ensure().fn_sig(def_id); } hir::ImplItemKind::Type(_) => { // Account for `type T = _;` let mut visitor = HirPlaceholderCollector::default(); visitor.visit_impl_item(impl_item); placeholder_type_error(tcx, None, visitor.0, false, None, "associated type"); } hir::ImplItemKind::Const(ty, _) => { // Account for `const T: _ = ..;` if !ty.is_suggestable_infer_ty() { let mut visitor = HirPlaceholderCollector::default(); visitor.visit_impl_item(impl_item); placeholder_type_error(tcx, None, visitor.0, false, None, "associated constant"); } } } } fn lower_variant_ctor(tcx: TyCtxt<'_>, def_id: LocalDefId) { tcx.ensure().generics_of(def_id); tcx.ensure().type_of(def_id); tcx.ensure().predicates_of(def_id); } fn lower_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId) { let def = tcx.adt_def(def_id); let repr_type = def.repr().discr_type(); let initial = repr_type.initial_discriminant(tcx); let mut prev_discr = None::>; // fill the discriminant values and field types for variant in def.variants() { let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx)); prev_discr = Some( if let ty::VariantDiscr::Explicit(const_def_id) = variant.discr { def.eval_explicit_discr(tcx, const_def_id).ok() } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) { Some(discr) } else { let span = tcx.def_span(variant.def_id); tcx.dcx().emit_err(errors::EnumDiscriminantOverflowed { span, discr: prev_discr.unwrap().to_string(), item_name: tcx.item_name(variant.def_id), wrapped_discr: wrapped_discr.to_string(), }); None } .unwrap_or(wrapped_discr), ); for f in &variant.fields { tcx.ensure().generics_of(f.did); tcx.ensure().type_of(f.did); tcx.ensure().predicates_of(f.did); } // Lower the ctor, if any. This also registers the variant as an item. if let Some(ctor_def_id) = variant.ctor_def_id() { lower_variant_ctor(tcx, ctor_def_id.expect_local()); } } } fn find_field(tcx: TyCtxt<'_>, (def_id, ident): (DefId, Ident)) -> Option { let adt = tcx.adt_def(def_id); if adt.is_enum() { return None; } adt.non_enum_variant().fields.iter_enumerated().find_map(|(idx, field)| { if field.is_unnamed() { let field_ty = tcx.type_of(field.did).instantiate_identity(); let adt_def = field_ty.ty_adt_def().expect("expect Adt for unnamed field"); tcx.find_field((adt_def.did(), ident)).map(|_| idx) } else { (field.ident(tcx).normalize_to_macros_2_0() == ident).then_some(idx) } }) } #[derive(Clone, Copy)] struct NestedSpan { span: Span, nested_field_span: Span, } impl NestedSpan { fn to_field_already_declared_nested_help(&self) -> errors::FieldAlreadyDeclaredNestedHelp { errors::FieldAlreadyDeclaredNestedHelp { span: self.span } } } #[derive(Clone, Copy)] enum FieldDeclSpan { NotNested(Span), Nested(NestedSpan), } impl From for FieldDeclSpan { fn from(span: Span) -> Self { Self::NotNested(span) } } impl From for FieldDeclSpan { fn from(span: NestedSpan) -> Self { Self::Nested(span) } } struct FieldUniquenessCheckContext<'tcx> { tcx: TyCtxt<'tcx>, seen_fields: FxIndexMap, } impl<'tcx> FieldUniquenessCheckContext<'tcx> { fn new(tcx: TyCtxt<'tcx>) -> Self { Self { tcx, seen_fields: FxIndexMap::default() } } /// Check if a given field `ident` declared at `field_decl` has been declared elsewhere before. fn check_field_decl(&mut self, ident: Ident, field_decl: FieldDeclSpan) { use FieldDeclSpan::*; let field_name = ident.name; let ident = ident.normalize_to_macros_2_0(); match (field_decl, self.seen_fields.get(&ident).copied()) { (NotNested(span), Some(NotNested(prev_span))) => { self.tcx.dcx().emit_err(errors::FieldAlreadyDeclared::NotNested { field_name, span, prev_span, }); } (NotNested(span), Some(Nested(prev))) => { self.tcx.dcx().emit_err(errors::FieldAlreadyDeclared::PreviousNested { field_name, span, prev_span: prev.span, prev_nested_field_span: prev.nested_field_span, prev_help: prev.to_field_already_declared_nested_help(), }); } ( Nested(current @ NestedSpan { span, nested_field_span, .. }), Some(NotNested(prev_span)), ) => { self.tcx.dcx().emit_err(errors::FieldAlreadyDeclared::CurrentNested { field_name, span, nested_field_span, help: current.to_field_already_declared_nested_help(), prev_span, }); } (Nested(current @ NestedSpan { span, nested_field_span }), Some(Nested(prev))) => { self.tcx.dcx().emit_err(errors::FieldAlreadyDeclared::BothNested { field_name, span, nested_field_span, help: current.to_field_already_declared_nested_help(), prev_span: prev.span, prev_nested_field_span: prev.nested_field_span, prev_help: prev.to_field_already_declared_nested_help(), }); } (field_decl, None) => { self.seen_fields.insert(ident, field_decl); } } } /// Check the uniqueness of fields across adt where there are /// nested fields imported from an unnamed field. fn check_field_in_nested_adt(&mut self, adt_def: ty::AdtDef<'_>, unnamed_field_span: Span) { for field in adt_def.all_fields() { if field.is_unnamed() { // Here we don't care about the generic parameters, so `instantiate_identity` is enough. match self.tcx.type_of(field.did).instantiate_identity().kind() { ty::Adt(adt_def, _) => { self.check_field_in_nested_adt(*adt_def, unnamed_field_span); } ty_kind => span_bug!( self.tcx.def_span(field.did), "Unexpected TyKind in FieldUniquenessCheckContext::check_field_in_nested_adt(): {ty_kind:?}" ), } } else { self.check_field_decl( field.ident(self.tcx), NestedSpan { span: unnamed_field_span, nested_field_span: self.tcx.def_span(field.did), } .into(), ); } } } /// Check the uniqueness of fields in a struct variant, and recursively /// check the nested fields if it is an unnamed field with type of an /// annoymous adt. fn check_field(&mut self, field: &hir::FieldDef<'_>) { if field.ident.name != kw::Underscore { self.check_field_decl(field.ident, field.span.into()); return; } match &field.ty.kind { hir::TyKind::AnonAdt(item_id) => { match &self.tcx.hir_node(item_id.hir_id()).expect_item().kind { hir::ItemKind::Struct(variant_data, ..) | hir::ItemKind::Union(variant_data, ..) => { variant_data.fields().iter().for_each(|f| self.check_field(f)); } item_kind => span_bug!( field.ty.span, "Unexpected ItemKind in FieldUniquenessCheckContext::check_field(): {item_kind:?}" ), } } hir::TyKind::Path(hir::QPath::Resolved(_, hir::Path { res, .. })) => { // If this is a direct path to an ADT, we can check it // If this is a type alias or non-ADT, `check_unnamed_fields` should verify it if let Some(def_id) = res.opt_def_id() && let Some(local) = def_id.as_local() && let Node::Item(item) = self.tcx.hir_node_by_def_id(local) && item.is_adt() { self.check_field_in_nested_adt(self.tcx.adt_def(def_id), field.span); } } // Abort due to errors (there must be an error if an unnamed field // has any type kind other than an anonymous adt or a named adt) ty_kind => { self.tcx.dcx().span_delayed_bug( field.ty.span, format!("Unexpected TyKind in FieldUniquenessCheckContext::check_field(): {ty_kind:?}"), ); // FIXME: errors during AST validation should abort the compilation before reaching here. self.tcx.dcx().abort_if_errors(); } } } } fn lower_variant( tcx: TyCtxt<'_>, variant_did: Option, ident: Ident, discr: ty::VariantDiscr, def: &hir::VariantData<'_>, adt_kind: ty::AdtKind, parent_did: LocalDefId, is_anonymous: bool, ) -> ty::VariantDef { let mut has_unnamed_fields = false; let mut field_uniqueness_check_ctx = FieldUniquenessCheckContext::new(tcx); let fields = def .fields() .iter() .inspect(|f| { has_unnamed_fields |= f.ident.name == kw::Underscore; // We only check named ADT here because anonymous ADTs are checked inside // the named ADT in which they are defined. if !is_anonymous { field_uniqueness_check_ctx.check_field(f); } }) .map(|f| ty::FieldDef { did: f.def_id.to_def_id(), name: f.ident.name, vis: tcx.visibility(f.def_id), }) .collect(); let recovered = matches!(def, hir::VariantData::Struct { recovered: Recovered::Yes(_), .. }); ty::VariantDef::new( ident.name, variant_did.map(LocalDefId::to_def_id), def.ctor().map(|(kind, _, def_id)| (kind, def_id.to_def_id())), discr, fields, adt_kind, parent_did.to_def_id(), recovered, adt_kind == AdtKind::Struct && tcx.has_attr(parent_did, sym::non_exhaustive) || variant_did .is_some_and(|variant_did| tcx.has_attr(variant_did, sym::non_exhaustive)), has_unnamed_fields, ) } fn adt_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::AdtDef<'_> { use rustc_hir::*; let Node::Item(item) = tcx.hir_node_by_def_id(def_id) else { bug!("expected ADT to be an item"); }; let is_anonymous = item.ident.name == kw::Empty; let repr = if is_anonymous { let parent = tcx.local_parent(def_id); if let Node::Item(item) = tcx.hir_node_by_def_id(parent) && item.is_struct_or_union() { tcx.adt_def(parent).repr() } else { tcx.dcx().span_delayed_bug(item.span, "anonymous field inside non struct/union"); ty::ReprOptions::default() } } else { tcx.repr_options_of_def(def_id) }; let (kind, variants) = match &item.kind { ItemKind::Enum(def, _) => { let mut distance_from_explicit = 0; let variants = def .variants .iter() .map(|v| { let discr = if let Some(e) = &v.disr_expr { distance_from_explicit = 0; ty::VariantDiscr::Explicit(e.def_id.to_def_id()) } else { ty::VariantDiscr::Relative(distance_from_explicit) }; distance_from_explicit += 1; lower_variant( tcx, Some(v.def_id), v.ident, discr, &v.data, AdtKind::Enum, def_id, is_anonymous, ) }) .collect(); (AdtKind::Enum, variants) } ItemKind::Struct(def, _) | ItemKind::Union(def, _) => { let adt_kind = match item.kind { ItemKind::Struct(..) => AdtKind::Struct, _ => AdtKind::Union, }; let variants = std::iter::once(lower_variant( tcx, None, item.ident, ty::VariantDiscr::Relative(0), def, adt_kind, def_id, is_anonymous, )) .collect(); (adt_kind, variants) } _ => bug!("{:?} is not an ADT", item.owner_id.def_id), }; tcx.mk_adt_def(def_id.to_def_id(), kind, variants, repr, is_anonymous) } fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef { let item = tcx.hir().expect_item(def_id); let (is_auto, safety, items) = match item.kind { hir::ItemKind::Trait(is_auto, safety, .., items) => { (is_auto == hir::IsAuto::Yes, safety, items) } hir::ItemKind::TraitAlias(..) => (false, hir::Safety::Safe, &[][..]), _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"), }; let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar); if paren_sugar && !tcx.features().unboxed_closures { tcx.dcx().emit_err(errors::ParenSugarAttribute { span: item.span }); } let is_marker = tcx.has_attr(def_id, sym::marker); let rustc_coinductive = tcx.has_attr(def_id, sym::rustc_coinductive); // FIXME: We could probably do way better attribute validation here. let mut skip_array_during_method_dispatch = false; let mut skip_boxed_slice_during_method_dispatch = false; for attr in tcx.get_attrs(def_id, sym::rustc_skip_during_method_dispatch) { if let Some(lst) = attr.meta_item_list() { for item in lst { if let Some(ident) = item.ident() { match ident.as_str() { "array" => skip_array_during_method_dispatch = true, "boxed_slice" => skip_boxed_slice_during_method_dispatch = true, _ => (), } } } } } let specialization_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) { ty::trait_def::TraitSpecializationKind::Marker } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) { ty::trait_def::TraitSpecializationKind::AlwaysApplicable } else { ty::trait_def::TraitSpecializationKind::None }; let must_implement_one_of = tcx .get_attr(def_id, sym::rustc_must_implement_one_of) // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]` // and that they are all identifiers .and_then(|attr| match attr.meta_item_list() { Some(items) if items.len() < 2 => { tcx.dcx().emit_err(errors::MustImplementOneOfAttribute { span: attr.span }); None } Some(items) => items .into_iter() .map(|item| item.ident().ok_or(item.span())) .collect::, _>>() .map_err(|span| { tcx.dcx().emit_err(errors::MustBeNameOfAssociatedFunction { span }); }) .ok() .zip(Some(attr.span)), // Error is reported by `rustc_attr!` None => None, }) // Check that all arguments of `#[rustc_must_implement_one_of]` reference // functions in the trait with default implementations .and_then(|(list, attr_span)| { let errors = list.iter().filter_map(|ident| { let item = items.iter().find(|item| item.ident == *ident); match item { Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => { if !tcx.defaultness(item.id.owner_id).has_value() { tcx.dcx().emit_err(errors::FunctionNotHaveDefaultImplementation { span: item.span, note_span: attr_span, }); return Some(()); } return None; } Some(item) => { tcx.dcx().emit_err(errors::MustImplementNotFunction { span: item.span, span_note: errors::MustImplementNotFunctionSpanNote { span: attr_span }, note: errors::MustImplementNotFunctionNote {}, }); } None => { tcx.dcx().emit_err(errors::FunctionNotFoundInTrait { span: ident.span }); } } Some(()) }); (errors.count() == 0).then_some(list) }) // Check for duplicates .and_then(|list| { let mut set: UnordMap = Default::default(); let mut no_dups = true; for ident in &*list { if let Some(dup) = set.insert(ident.name, ident.span) { tcx.dcx() .emit_err(errors::FunctionNamesDuplicated { spans: vec![dup, ident.span] }); no_dups = false; } } no_dups.then_some(list) }); let mut deny_explicit_impl = false; let mut implement_via_object = true; if let Some(attr) = tcx.get_attr(def_id, sym::rustc_deny_explicit_impl) { deny_explicit_impl = true; let mut seen_attr = false; for meta in attr.meta_item_list().iter().flatten() { if let Some(meta) = meta.meta_item() && meta.name_or_empty() == sym::implement_via_object && let Some(lit) = meta.name_value_literal() { if seen_attr { tcx.dcx().span_err(meta.span, "duplicated `implement_via_object` meta item"); } seen_attr = true; match lit.symbol { kw::True => { implement_via_object = true; } kw::False => { implement_via_object = false; } _ => { tcx.dcx().span_err( meta.span, format!( "unknown literal passed to `implement_via_object` attribute: {}", lit.symbol ), ); } } } else { tcx.dcx().span_err( meta.span(), format!("unknown meta item passed to `rustc_deny_explicit_impl` {meta:?}"), ); } } if !seen_attr { tcx.dcx().span_err(attr.span, "missing `implement_via_object` meta item"); } } ty::TraitDef { def_id: def_id.to_def_id(), safety, paren_sugar, has_auto_impl: is_auto, is_marker, is_coinductive: rustc_coinductive || is_auto, skip_array_during_method_dispatch, skip_boxed_slice_during_method_dispatch, specialization_kind, must_implement_one_of, implement_via_object, deny_explicit_impl, } } #[instrument(level = "debug", skip(tcx))] fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFnSig<'_>> { use rustc_hir::Node::*; use rustc_hir::*; let hir_id = tcx.local_def_id_to_hir_id(def_id); let icx = ItemCtxt::new(tcx, def_id); let output = match tcx.hir_node(hir_id) { TraitItem(hir::TraitItem { kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)), generics, .. }) | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => { infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx) } ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => { // Do not try to infer the return type for a impl method coming from a trait if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) = tcx.parent_hir_node(hir_id) && i.of_trait.is_some() { icx.lowerer().lower_fn_ty( hir_id, sig.header.safety, sig.header.abi, sig.decl, Some(generics), None, ) } else { infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx) } } TraitItem(hir::TraitItem { kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _), generics, .. }) => { icx.lowerer().lower_fn_ty(hir_id, header.safety, header.abi, decl, Some(generics), None) } ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _, safety), .. }) => { let abi = tcx.hir().get_foreign_abi(hir_id); compute_sig_of_foreign_fn_decl(tcx, def_id, fn_decl, abi, safety) } Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor().is_some() => { let adt_def_id = tcx.hir().get_parent_item(hir_id).def_id.to_def_id(); let ty = tcx.type_of(adt_def_id).instantiate_identity(); let inputs = data.fields().iter().map(|f| tcx.type_of(f.def_id).instantiate_identity()); // constructors for structs with `layout_scalar_valid_range` are unsafe to call let safety = match tcx.layout_scalar_valid_range(adt_def_id) { (Bound::Unbounded, Bound::Unbounded) => hir::Safety::Safe, _ => hir::Safety::Unsafe, }; ty::Binder::dummy(tcx.mk_fn_sig(inputs, ty, false, safety, abi::Abi::Rust)) } Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => { // Closure signatures are not like other function // signatures and cannot be accessed through `fn_sig`. For // example, a closure signature excludes the `self` // argument. In any case they are embedded within the // closure type as part of the `ClosureArgs`. // // To get the signature of a closure, you should use the // `sig` method on the `ClosureArgs`: // // args.as_closure().sig(def_id, tcx) bug!("to get the signature of a closure, use `args.as_closure().sig()` not `fn_sig()`",); } x => { bug!("unexpected sort of node in fn_sig(): {:?}", x); } }; ty::EarlyBinder::bind(output) } fn infer_return_ty_for_fn_sig<'tcx>( tcx: TyCtxt<'tcx>, sig: &hir::FnSig<'tcx>, generics: &hir::Generics<'_>, def_id: LocalDefId, icx: &ItemCtxt<'tcx>, ) -> ty::PolyFnSig<'tcx> { let hir_id = tcx.local_def_id_to_hir_id(def_id); match sig.decl.output.get_infer_ret_ty() { Some(ty) => { let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id]; // Typeck doesn't expect erased regions to be returned from `type_of`. let fn_sig = tcx.fold_regions(fn_sig, |r, _| match *r { ty::ReErased => tcx.lifetimes.re_static, _ => r, }); let mut visitor = HirPlaceholderCollector::default(); visitor.visit_ty(ty); let mut diag = bad_placeholder(tcx, visitor.0, "return type"); let ret_ty = fn_sig.output(); // Don't leak types into signatures unless they're nameable! // For example, if a function returns itself, we don't want that // recursive function definition to leak out into the fn sig. let mut recovered_ret_ty = None; if let Some(suggestable_ret_ty) = ret_ty.make_suggestable(tcx, false, None) { diag.span_suggestion( ty.span, "replace with the correct return type", suggestable_ret_ty, Applicability::MachineApplicable, ); recovered_ret_ty = Some(suggestable_ret_ty); } else if let Some(sugg) = suggest_impl_trait(&tcx.infer_ctxt().build(), tcx.param_env(def_id), ret_ty) { diag.span_suggestion( ty.span, "replace with an appropriate return type", sugg, Applicability::MachineApplicable, ); } else if ret_ty.is_closure() { diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound"); } // Also note how `Fn` traits work just in case! if ret_ty.is_closure() { diag.note( "for more information on `Fn` traits and closure types, see \ https://doc.rust-lang.org/book/ch13-01-closures.html", ); } let guar = diag.emit(); ty::Binder::dummy(tcx.mk_fn_sig( fn_sig.inputs().iter().copied(), recovered_ret_ty.unwrap_or_else(|| Ty::new_error(tcx, guar)), fn_sig.c_variadic, fn_sig.safety, fn_sig.abi, )) } None => icx.lowerer().lower_fn_ty( hir_id, sig.header.safety, sig.header.abi, sig.decl, Some(generics), None, ), } } pub fn suggest_impl_trait<'tcx>( infcx: &InferCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, ret_ty: Ty<'tcx>, ) -> Option { let format_as_assoc: fn(_, _, _, _, _) -> _ = |tcx: TyCtxt<'tcx>, _: ty::GenericArgsRef<'tcx>, trait_def_id: DefId, assoc_item_def_id: DefId, item_ty: Ty<'tcx>| { let trait_name = tcx.item_name(trait_def_id); let assoc_name = tcx.item_name(assoc_item_def_id); Some(format!("impl {trait_name}<{assoc_name} = {item_ty}>")) }; let format_as_parenthesized: fn(_, _, _, _, _) -> _ = |tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>, trait_def_id: DefId, _: DefId, item_ty: Ty<'tcx>| { let trait_name = tcx.item_name(trait_def_id); let args_tuple = args.type_at(1); let ty::Tuple(types) = *args_tuple.kind() else { return None; }; let types = types.make_suggestable(tcx, false, None)?; let maybe_ret = if item_ty.is_unit() { String::new() } else { format!(" -> {item_ty}") }; Some(format!( "impl {trait_name}({}){maybe_ret}", types.iter().map(|ty| ty.to_string()).collect::>().join(", ") )) }; for (trait_def_id, assoc_item_def_id, formatter) in [ ( infcx.tcx.get_diagnostic_item(sym::Iterator), infcx.tcx.get_diagnostic_item(sym::IteratorItem), format_as_assoc, ), ( infcx.tcx.lang_items().future_trait(), infcx.tcx.lang_items().future_output(), format_as_assoc, ), ( infcx.tcx.lang_items().fn_trait(), infcx.tcx.lang_items().fn_once_output(), format_as_parenthesized, ), ( infcx.tcx.lang_items().fn_mut_trait(), infcx.tcx.lang_items().fn_once_output(), format_as_parenthesized, ), ( infcx.tcx.lang_items().fn_once_trait(), infcx.tcx.lang_items().fn_once_output(), format_as_parenthesized, ), ] { let Some(trait_def_id) = trait_def_id else { continue; }; let Some(assoc_item_def_id) = assoc_item_def_id else { continue; }; if infcx.tcx.def_kind(assoc_item_def_id) != DefKind::AssocTy { continue; } let sugg = infcx.probe(|_| { let args = ty::GenericArgs::for_item(infcx.tcx, trait_def_id, |param, _| { if param.index == 0 { ret_ty.into() } else { infcx.var_for_def(DUMMY_SP, param) } }); if !infcx .type_implements_trait(trait_def_id, args, param_env) .must_apply_modulo_regions() { return None; } let ocx = ObligationCtxt::new(&infcx); let item_ty = ocx.normalize( &ObligationCause::dummy(), param_env, Ty::new_projection(infcx.tcx, assoc_item_def_id, args), ); // FIXME(compiler-errors): We may benefit from resolving regions here. if ocx.select_where_possible().is_empty() && let item_ty = infcx.resolve_vars_if_possible(item_ty) && let Some(item_ty) = item_ty.make_suggestable(infcx.tcx, false, None) && let Some(sugg) = formatter( infcx.tcx, infcx.resolve_vars_if_possible(args), trait_def_id, assoc_item_def_id, item_ty, ) { return Some(sugg); } None }); if sugg.is_some() { return sugg; } } None } fn impl_trait_header(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option> { let icx = ItemCtxt::new(tcx, def_id); let item = tcx.hir().expect_item(def_id); let impl_ = item.expect_impl(); impl_ .of_trait .as_ref() .map(|hir_trait_ref| { let self_ty = tcx.type_of(def_id).instantiate_identity(); let trait_ref = if let Some(ErrorGuaranteed { .. }) = check_impl_constness( tcx, tcx.is_const_trait_impl_raw(def_id.to_def_id()), hir_trait_ref, ) { // we have a const impl, but for a trait without `#[const_trait]`, so // without the host param. If we continue with the HIR trait ref, we get // ICEs for generic arg count mismatch. We do a little HIR editing to // make HIR ty lowering happy. let mut path_segments = hir_trait_ref.path.segments.to_vec(); let last_segment = path_segments.len() - 1; let mut args = *path_segments[last_segment].args(); let last_arg = args.args.len() - 1; assert!(matches!(args.args[last_arg], hir::GenericArg::Const(anon_const) if anon_const.is_desugared_from_effects)); args.args = &args.args[..args.args.len() - 1]; path_segments[last_segment].args = Some(tcx.hir_arena.alloc(args)); let path = hir::Path { span: hir_trait_ref.path.span, res: hir_trait_ref.path.res, segments: tcx.hir_arena.alloc_slice(&path_segments), }; let trait_ref = tcx.hir_arena.alloc(hir::TraitRef { path: tcx.hir_arena.alloc(path), hir_ref_id: hir_trait_ref.hir_ref_id }); icx.lowerer().lower_impl_trait_ref(trait_ref, self_ty) } else { icx.lowerer().lower_impl_trait_ref(hir_trait_ref, self_ty) }; ty::ImplTraitHeader { trait_ref: ty::EarlyBinder::bind(trait_ref), safety: impl_.safety, polarity: polarity_of_impl(tcx, def_id, impl_, item.span) } }) } fn check_impl_constness( tcx: TyCtxt<'_>, is_const: bool, hir_trait_ref: &hir::TraitRef<'_>, ) -> Option { if !is_const { return None; } let trait_def_id = hir_trait_ref.trait_def_id()?; if tcx.has_attr(trait_def_id, sym::const_trait) { return None; } let trait_name = tcx.item_name(trait_def_id).to_string(); Some(tcx.dcx().emit_err(errors::ConstImplForNonConstTrait { trait_ref_span: hir_trait_ref.path.span, trait_name, local_trait_span: trait_def_id.as_local().map(|_| tcx.def_span(trait_def_id).shrink_to_lo()), marking: (), adding: (), })) } fn polarity_of_impl( tcx: TyCtxt<'_>, def_id: LocalDefId, impl_: &hir::Impl<'_>, span: Span, ) -> ty::ImplPolarity { let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl); match &impl_ { hir::Impl { polarity: hir::ImplPolarity::Negative(span), of_trait, .. } => { if is_rustc_reservation { let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span)); tcx.dcx().span_err(span, "reservation impls can't be negative"); } ty::ImplPolarity::Negative } hir::Impl { polarity: hir::ImplPolarity::Positive, of_trait: None, .. } => { if is_rustc_reservation { tcx.dcx().span_err(span, "reservation impls can't be inherent"); } ty::ImplPolarity::Positive } hir::Impl { polarity: hir::ImplPolarity::Positive, of_trait: Some(_), .. } => { if is_rustc_reservation { ty::ImplPolarity::Reservation } else { ty::ImplPolarity::Positive } } } } /// Returns the early-bound lifetimes declared in this generics /// listing. For anything other than fns/methods, this is just all /// the lifetimes that are declared. For fns or methods, we have to /// screen out those that do not appear in any where-clauses etc using /// `resolve_lifetime::early_bound_lifetimes`. fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>( tcx: TyCtxt<'tcx>, generics: &'a hir::Generics<'a>, ) -> impl Iterator> + Captures<'tcx> { generics.params.iter().filter(move |param| match param.kind { GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id), _ => false, }) } /// Returns a list of type predicates for the definition with ID `def_id`, including inferred /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus /// inferred constraints concerning which regions outlive other regions. #[instrument(level = "debug", skip(tcx))] fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> { let mut result = tcx.explicit_predicates_of(def_id); debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result); let inferred_outlives = tcx.inferred_outlives_of(def_id); if !inferred_outlives.is_empty() { debug!( "predicates_defined_on: inferred_outlives_of({:?}) = {:?}", def_id, inferred_outlives, ); let inferred_outlives_iter = inferred_outlives.iter().map(|(clause, span)| ((*clause).upcast(tcx), *span)); if result.predicates.is_empty() { result.predicates = tcx.arena.alloc_from_iter(inferred_outlives_iter); } else { result.predicates = tcx.arena.alloc_from_iter( result.predicates.into_iter().copied().chain(inferred_outlives_iter), ); } } debug!("predicates_defined_on({:?}) = {:?}", def_id, result); result } fn compute_sig_of_foreign_fn_decl<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, decl: &'tcx hir::FnDecl<'tcx>, abi: abi::Abi, safety: hir::Safety, ) -> ty::PolyFnSig<'tcx> { let safety = if abi == abi::Abi::RustIntrinsic { intrinsic_operation_unsafety(tcx, def_id) } else { safety }; let hir_id = tcx.local_def_id_to_hir_id(def_id); let fty = ItemCtxt::new(tcx, def_id).lowerer().lower_fn_ty(hir_id, safety, abi, decl, None, None); // Feature gate SIMD types in FFI, since I am not sure that the // ABIs are handled at all correctly. -huonw if abi != abi::Abi::RustIntrinsic && !tcx.features().simd_ffi { let check = |hir_ty: &hir::Ty<'_>, ty: Ty<'_>| { if ty.is_simd() { let snip = tcx .sess .source_map() .span_to_snippet(hir_ty.span) .map_or_else(|_| String::new(), |s| format!(" `{s}`")); tcx.dcx().emit_err(errors::SIMDFFIHighlyExperimental { span: hir_ty.span, snip }); } }; for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) { check(input, *ty) } if let hir::FnRetTy::Return(ty) = decl.output { check(ty, fty.output().skip_binder()) } } fty } fn coroutine_kind(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option { match tcx.hir_node_by_def_id(def_id) { Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure(&rustc_hir::Closure { kind: hir::ClosureKind::Coroutine(kind), .. }), .. }) => Some(kind), _ => None, } } fn coroutine_for_closure(tcx: TyCtxt<'_>, def_id: LocalDefId) -> DefId { let &rustc_hir::Closure { kind: hir::ClosureKind::CoroutineClosure(_), body, .. } = tcx.hir_node_by_def_id(def_id).expect_closure() else { bug!() }; let &hir::Expr { kind: hir::ExprKind::Closure(&rustc_hir::Closure { def_id, kind: hir::ClosureKind::Coroutine(_), .. }), .. } = tcx.hir().body(body).value else { bug!() }; def_id.to_def_id() } fn is_type_alias_impl_trait<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> bool { match tcx.hir_node_by_def_id(def_id) { Node::Item(hir::Item { kind: hir::ItemKind::OpaqueTy(opaque), .. }) => { matches!(opaque.origin, hir::OpaqueTyOrigin::TyAlias { .. }) } _ => bug!("tried getting opaque_ty_origin for non-opaque: {:?}", def_id), } }