use crate::check::intrinsicck::InlineAsmCtxt; use crate::errors::{self, LinkageType}; use super::compare_impl_item::check_type_bounds; use super::compare_impl_item::{compare_impl_method, compare_impl_ty}; use super::*; use rustc_attr as attr; use rustc_errors::{Applicability, ErrorGuaranteed, MultiSpan}; use rustc_hir as hir; use rustc_hir::def::{CtorKind, DefKind, Res}; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::Visitor; use rustc_hir::{ItemKind, Node, PathSegment}; use rustc_infer::infer::opaque_types::ConstrainOpaqueTypeRegionVisitor; use rustc_infer::infer::outlives::env::OutlivesEnvironment; use rustc_infer::infer::{DefiningAnchor, RegionVariableOrigin, TyCtxtInferExt}; use rustc_infer::traits::{Obligation, TraitEngineExt as _}; use rustc_lint::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS; use rustc_middle::hir::nested_filter; use rustc_middle::middle::stability::EvalResult; use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES}; use rustc_middle::ty::subst::GenericArgKind; use rustc_middle::ty::util::{Discr, IntTypeExt}; use rustc_middle::ty::{ self, AdtDef, ParamEnv, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, }; use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVENTIONS}; use rustc_span::symbol::sym; use rustc_span::{self, Span}; use rustc_target::abi::FieldIdx; use rustc_target::spec::abi::Abi; use rustc_trait_selection::traits::error_reporting::on_unimplemented::OnUnimplementedDirective; use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _; use rustc_trait_selection::traits::{self, ObligationCtxt, TraitEngine, TraitEngineExt as _}; use std::ops::ControlFlow; pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) { match tcx.sess.target.is_abi_supported(abi) { Some(true) => (), Some(false) => { struct_span_err!( tcx.sess, span, E0570, "`{abi}` is not a supported ABI for the current target", ) .emit(); } None => { tcx.struct_span_lint_hir( UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, "use of calling convention not supported on this target", |lint| lint, ); } } // This ABI is only allowed on function pointers if abi == Abi::CCmseNonSecureCall { struct_span_err!( tcx.sess, span, E0781, "the `\"C-cmse-nonsecure-call\"` ABI is only allowed on function pointers" ) .emit(); } } fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) { let def = tcx.adt_def(def_id); let span = tcx.def_span(def_id); def.destructor(tcx); // force the destructor to be evaluated if def.repr().simd() { check_simd(tcx, span, def_id); } check_transparent(tcx, def); check_packed(tcx, span, def); } fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) { let def = tcx.adt_def(def_id); let span = tcx.def_span(def_id); def.destructor(tcx); // force the destructor to be evaluated check_transparent(tcx, def); check_union_fields(tcx, span, def_id); check_packed(tcx, span, def); } /// Check that the fields of the `union` do not need dropping. fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool { let item_type = tcx.type_of(item_def_id).subst_identity(); if let ty::Adt(def, substs) = item_type.kind() { assert!(def.is_union()); fn allowed_union_field<'tcx>( ty: Ty<'tcx>, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, ) -> bool { // We don't just accept all !needs_drop fields, due to semver concerns. match ty.kind() { ty::Ref(..) => true, // references never drop (even mutable refs, which are non-Copy and hence fail the later check) ty::Tuple(tys) => { // allow tuples of allowed types tys.iter().all(|ty| allowed_union_field(ty, tcx, param_env)) } ty::Array(elem, _len) => { // Like `Copy`, we do *not* special-case length 0. allowed_union_field(*elem, tcx, param_env) } _ => { // Fallback case: allow `ManuallyDrop` and things that are `Copy`, // also no need to report an error if the type is unresolved. ty.ty_adt_def().is_some_and(|adt_def| adt_def.is_manually_drop()) || ty.is_copy_modulo_regions(tcx, param_env) || ty.references_error() } } } let param_env = tcx.param_env(item_def_id); for field in &def.non_enum_variant().fields { let field_ty = tcx.normalize_erasing_regions(param_env, field.ty(tcx, substs)); if !allowed_union_field(field_ty, tcx, param_env) { let (field_span, ty_span) = match tcx.hir().get_if_local(field.did) { // We are currently checking the type this field came from, so it must be local. Some(Node::Field(field)) => (field.span, field.ty.span), _ => unreachable!("mir field has to correspond to hir field"), }; tcx.sess.emit_err(errors::InvalidUnionField { field_span, sugg: errors::InvalidUnionFieldSuggestion { lo: ty_span.shrink_to_lo(), hi: ty_span.shrink_to_hi(), }, note: (), }); return false; } else if field_ty.needs_drop(tcx, param_env) { // This should never happen. But we can get here e.g. in case of name resolution errors. tcx.sess.delay_span_bug(span, "we should never accept maybe-dropping union fields"); } } } else { span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind()); } true } /// Check that a `static` is inhabited. fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) { // Make sure statics are inhabited. // Other parts of the compiler assume that there are no uninhabited places. In principle it // would be enough to check this for `extern` statics, as statics with an initializer will // have UB during initialization if they are uninhabited, but there also seems to be no good // reason to allow any statics to be uninhabited. let ty = tcx.type_of(def_id).subst_identity(); let span = tcx.def_span(def_id); let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) { Ok(l) => l, // Foreign statics that overflow their allowed size should emit an error Err(LayoutError::SizeOverflow(_)) if matches!(tcx.def_kind(def_id), DefKind::Static(_) if tcx.def_kind(tcx.local_parent(def_id)) == DefKind::ForeignMod) => { tcx.sess .struct_span_err(span, "extern static is too large for the current architecture") .emit(); return; } // Generic statics are rejected, but we still reach this case. Err(e) => { tcx.sess.delay_span_bug(span, &e.to_string()); return; } }; if layout.abi.is_uninhabited() { tcx.struct_span_lint_hir( UNINHABITED_STATIC, tcx.hir().local_def_id_to_hir_id(def_id), span, "static of uninhabited type", |lint| { lint .note("uninhabited statics cannot be initialized, and any access would be an immediate error") }, ); } } /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo` /// projections that would result in "inheriting lifetimes". fn check_opaque(tcx: TyCtxt<'_>, id: hir::ItemId) { let item = tcx.hir().item(id); let hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) = item.kind else { tcx.sess.delay_span_bug(item.span, "expected opaque item"); return; }; // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting // `async-std` (and `pub async fn` in general). // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it! // See https://github.com/rust-lang/rust/issues/75100 if tcx.sess.opts.actually_rustdoc { return; } let substs = InternalSubsts::identity_for_item(tcx, item.owner_id); let span = tcx.def_span(item.owner_id.def_id); if !tcx.features().impl_trait_projections { check_opaque_for_inheriting_lifetimes(tcx, item.owner_id.def_id, span); } if tcx.type_of(item.owner_id.def_id).subst_identity().references_error() { return; } if check_opaque_for_cycles(tcx, item.owner_id.def_id, substs, span, &origin).is_err() { return; } check_opaque_meets_bounds(tcx, item.owner_id.def_id, substs, span, &origin); } /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result /// in "inheriting lifetimes". #[instrument(level = "debug", skip(tcx, span))] pub(super) fn check_opaque_for_inheriting_lifetimes( tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span, ) { let item = tcx.hir().expect_item(def_id); debug!(?item, ?span); struct ProhibitOpaqueVisitor<'tcx> { tcx: TyCtxt<'tcx>, opaque_identity_ty: Ty<'tcx>, parent_count: u32, references_parent_regions: bool, selftys: Vec<(Span, Option)>, } impl<'tcx> ty::visit::TypeVisitor> for ProhibitOpaqueVisitor<'tcx> { type BreakTy = Ty<'tcx>; fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow { debug!(?t, "root_visit_ty"); if t == self.opaque_identity_ty { ControlFlow::Continue(()) } else { t.visit_with(&mut ConstrainOpaqueTypeRegionVisitor { tcx: self.tcx, op: |region| { if let ty::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = *region && index < self.parent_count { self.references_parent_regions= true; } }, }); if self.references_parent_regions { ControlFlow::Break(t) } else { ControlFlow::Continue(()) } } } } impl<'tcx> Visitor<'tcx> for ProhibitOpaqueVisitor<'tcx> { type NestedFilter = nested_filter::OnlyBodies; fn nested_visit_map(&mut self) -> Self::Map { self.tcx.hir() } fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) { match arg.kind { hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments { [PathSegment { res: Res::SelfTyParam { .. }, .. }] => { let impl_ty_name = None; self.selftys.push((path.span, impl_ty_name)); } [PathSegment { res: Res::SelfTyAlias { alias_to: def_id, .. }, .. }] => { let impl_ty_name = Some(self.tcx.def_path_str(*def_id)); self.selftys.push((path.span, impl_ty_name)); } _ => {} }, _ => {} } hir::intravisit::walk_ty(self, arg); } } if let ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..), in_trait, .. }) = item.kind { let substs = InternalSubsts::identity_for_item(tcx, def_id); let opaque_identity_ty = if in_trait && !tcx.lower_impl_trait_in_trait_to_assoc_ty() { tcx.mk_projection(def_id.to_def_id(), substs) } else { tcx.mk_opaque(def_id.to_def_id(), substs) }; let mut visitor = ProhibitOpaqueVisitor { opaque_identity_ty, parent_count: tcx.generics_of(def_id).parent_count as u32, references_parent_regions: false, tcx, selftys: vec![], }; let prohibit_opaque = tcx .explicit_item_bounds(def_id) .iter() .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor)); if let Some(ty) = prohibit_opaque.break_value() { visitor.visit_item(&item); let is_async = match item.kind { ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => { matches!(origin, hir::OpaqueTyOrigin::AsyncFn(..)) } _ => unreachable!(), }; let mut err = feature_err( &tcx.sess.parse_sess, sym::impl_trait_projections, span, &format!( "`{}` return type cannot contain a projection or `Self` that references \ lifetimes from a parent scope", if is_async { "async fn" } else { "impl Trait" }, ), ); for (span, name) in visitor.selftys { err.span_suggestion( span, "consider spelling out the type instead", name.unwrap_or_else(|| format!("{:?}", ty)), Applicability::MaybeIncorrect, ); } err.emit(); } } } /// Checks that an opaque type does not contain cycles. pub(super) fn check_opaque_for_cycles<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, substs: SubstsRef<'tcx>, span: Span, origin: &hir::OpaqueTyOrigin, ) -> Result<(), ErrorGuaranteed> { if tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs).is_err() { let reported = match origin { hir::OpaqueTyOrigin::AsyncFn(..) => async_opaque_type_cycle_error(tcx, span), _ => opaque_type_cycle_error(tcx, def_id, span), }; Err(reported) } else { Ok(()) } } /// Check that the concrete type behind `impl Trait` actually implements `Trait`. /// /// This is mostly checked at the places that specify the opaque type, but we /// check those cases in the `param_env` of that function, which may have /// bounds not on this opaque type: /// /// ```ignore (illustrative) /// type X = impl Clone; /// fn f(t: T) -> X { /// t /// } /// ``` /// /// Without this check the above code is incorrectly accepted: we would ICE if /// some tried, for example, to clone an `Option>`. #[instrument(level = "debug", skip(tcx))] fn check_opaque_meets_bounds<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, substs: SubstsRef<'tcx>, span: Span, origin: &hir::OpaqueTyOrigin, ) { let defining_use_anchor = match *origin { hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) => did, hir::OpaqueTyOrigin::TyAlias => def_id, }; let param_env = tcx.param_env(defining_use_anchor); let infcx = tcx .infer_ctxt() .with_opaque_type_inference(DefiningAnchor::Bind(defining_use_anchor)) .build(); let ocx = ObligationCtxt::new(&infcx); let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs); // `ReErased` regions appear in the "parent_substs" of closures/generators. // We're ignoring them here and replacing them with fresh region variables. // See tests in ui/type-alias-impl-trait/closure_{parent_substs,wf_outlives}.rs. // // FIXME: Consider wrapping the hidden type in an existential `Binder` and instantiating it // here rather than using ReErased. let hidden_ty = tcx.type_of(def_id.to_def_id()).subst(tcx, substs); let hidden_ty = tcx.fold_regions(hidden_ty, |re, _dbi| match re.kind() { ty::ReErased => infcx.next_region_var(RegionVariableOrigin::MiscVariable(span)), _ => re, }); let misc_cause = traits::ObligationCause::misc(span, def_id); match ocx.eq(&misc_cause, param_env, opaque_ty, hidden_ty) { Ok(()) => {} Err(ty_err) => { let ty_err = ty_err.to_string(tcx); tcx.sess.delay_span_bug( span, &format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"), ); } } // Additionally require the hidden type to be well-formed with only the generics of the opaque type. // Defining use functions may have more bounds than the opaque type, which is ok, as long as the // hidden type is well formed even without those bounds. let predicate = ty::Binder::dummy(ty::PredicateKind::WellFormed(hidden_ty.into())); ocx.register_obligation(Obligation::new(tcx, misc_cause, param_env, predicate)); // Check that all obligations are satisfied by the implementation's // version. let errors = ocx.select_all_or_error(); if !errors.is_empty() { infcx.err_ctxt().report_fulfillment_errors(&errors); } match origin { // Checked when type checking the function containing them. hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => {} // Can have different predicates to their defining use hir::OpaqueTyOrigin::TyAlias => { let outlives_env = OutlivesEnvironment::new(param_env); let _ = ocx.resolve_regions_and_report_errors(defining_use_anchor, &outlives_env); } } // Clean up after ourselves let _ = infcx.take_opaque_types(); } fn is_enum_of_nonnullable_ptr<'tcx>( tcx: TyCtxt<'tcx>, adt_def: AdtDef<'tcx>, substs: SubstsRef<'tcx>, ) -> bool { if adt_def.repr().inhibit_enum_layout_opt() { return false; } let [var_one, var_two] = &adt_def.variants().raw[..] else { return false; }; let (([], [field]) | ([field], [])) = (&var_one.fields.raw[..], &var_two.fields.raw[..]) else { return false; }; matches!(field.ty(tcx, substs).kind(), ty::FnPtr(..) | ty::Ref(..)) } fn check_static_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) { if tcx.codegen_fn_attrs(def_id).import_linkage.is_some() { if match tcx.type_of(def_id).subst_identity().kind() { ty::RawPtr(_) => false, ty::Adt(adt_def, substs) => !is_enum_of_nonnullable_ptr(tcx, *adt_def, *substs), _ => true, } { tcx.sess.emit_err(LinkageType { span: tcx.def_span(def_id) }); } } } fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) { debug!( "check_item_type(it.def_id={:?}, it.name={})", id.owner_id, tcx.def_path_str(id.owner_id.to_def_id()) ); let _indenter = indenter(); match tcx.def_kind(id.owner_id) { DefKind::Static(..) => { tcx.ensure().typeck(id.owner_id.def_id); maybe_check_static_with_link_section(tcx, id.owner_id.def_id); check_static_inhabited(tcx, id.owner_id.def_id); check_static_linkage(tcx, id.owner_id.def_id); } DefKind::Const => { tcx.ensure().typeck(id.owner_id.def_id); } DefKind::Enum => { check_enum(tcx, id.owner_id.def_id); } DefKind::Fn => {} // entirely within check_item_body DefKind::Impl { of_trait } => { if of_trait && let Some(impl_trait_ref) = tcx.impl_trait_ref(id.owner_id) { check_impl_items_against_trait( tcx, id.owner_id.def_id, impl_trait_ref.subst_identity(), ); check_on_unimplemented(tcx, id); } } DefKind::Trait => { let assoc_items = tcx.associated_items(id.owner_id); check_on_unimplemented(tcx, id); for &assoc_item in assoc_items.in_definition_order() { match assoc_item.kind { ty::AssocKind::Fn => { let abi = tcx.fn_sig(assoc_item.def_id).skip_binder().abi(); fn_maybe_err(tcx, assoc_item.ident(tcx).span, abi); } ty::AssocKind::Type if assoc_item.defaultness(tcx).has_value() => { let trait_substs = InternalSubsts::identity_for_item(tcx, id.owner_id); let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds( tcx, assoc_item, assoc_item, tcx.mk_trait_ref(id.owner_id.to_def_id(), trait_substs), ); } _ => {} } } } DefKind::Struct => { check_struct(tcx, id.owner_id.def_id); } DefKind::Union => { check_union(tcx, id.owner_id.def_id); } DefKind::OpaqueTy => { let opaque = tcx.hir().expect_item(id.owner_id.def_id).expect_opaque_ty(); if let hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id) = opaque.origin && let hir::Node::TraitItem(trait_item) = tcx.hir().get_by_def_id(fn_def_id) && let (_, hir::TraitFn::Required(..)) = trait_item.expect_fn() { // Skip opaques from RPIT in traits with no default body. } else { check_opaque(tcx, id); } } DefKind::ImplTraitPlaceholder => { let parent = tcx.impl_trait_in_trait_parent_fn(id.owner_id.to_def_id()); // Only check the validity of this opaque type if the function has a default body if let hir::Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)), .. }) = tcx.hir().get_by_def_id(parent.expect_local()) { check_opaque(tcx, id); } } DefKind::TyAlias => { let pty_ty = tcx.type_of(id.owner_id).subst_identity(); let generics = tcx.generics_of(id.owner_id); check_type_params_are_used(tcx, &generics, pty_ty); } DefKind::ForeignMod => { let it = tcx.hir().item(id); let hir::ItemKind::ForeignMod { abi, items } = it.kind else { return; }; check_abi(tcx, it.hir_id(), it.span, abi); match abi { Abi::RustIntrinsic => { for item in items { let item = tcx.hir().foreign_item(item.id); intrinsic::check_intrinsic_type(tcx, item); } } Abi::PlatformIntrinsic => { for item in items { let item = tcx.hir().foreign_item(item.id); intrinsic::check_platform_intrinsic_type(tcx, item); } } _ => { for item in items { let def_id = item.id.owner_id.def_id; let generics = tcx.generics_of(def_id); let own_counts = generics.own_counts(); if generics.params.len() - own_counts.lifetimes != 0 { let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) { (_, 0) => ("type", "types", Some("u32")), // We don't specify an example value, because we can't generate // a valid value for any type. (0, _) => ("const", "consts", None), _ => ("type or const", "types or consts", None), }; struct_span_err!( tcx.sess, item.span, E0044, "foreign items may not have {kinds} parameters", ) .span_label(item.span, &format!("can't have {kinds} parameters")) .help( // FIXME: once we start storing spans for type arguments, turn this // into a suggestion. &format!( "replace the {} parameters with concrete {}{}", kinds, kinds_pl, egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(), ), ) .emit(); } let item = tcx.hir().foreign_item(item.id); match &item.kind { hir::ForeignItemKind::Fn(fn_decl, _, _) => { require_c_abi_if_c_variadic(tcx, fn_decl, abi, item.span); } hir::ForeignItemKind::Static(..) => { check_static_inhabited(tcx, def_id); check_static_linkage(tcx, def_id); } _ => {} } } } } } DefKind::GlobalAsm => { let it = tcx.hir().item(id); let hir::ItemKind::GlobalAsm(asm) = it.kind else { span_bug!(it.span, "DefKind::GlobalAsm but got {:#?}", it) }; InlineAsmCtxt::new_global_asm(tcx).check_asm(asm, id.owner_id.def_id); } _ => {} } } pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, item: hir::ItemId) { // an error would be reported if this fails. let _ = OnUnimplementedDirective::of_item(tcx, item.owner_id.to_def_id()); } pub(super) fn check_specialization_validity<'tcx>( tcx: TyCtxt<'tcx>, trait_def: &ty::TraitDef, trait_item: ty::AssocItem, impl_id: DefId, impl_item: DefId, ) { let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) else { return }; let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| { if parent.is_from_trait() { None } else { Some((parent, parent.item(tcx, trait_item.def_id))) } }); let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| { match parent_item { // Parent impl exists, and contains the parent item we're trying to specialize, but // doesn't mark it `default`. Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => { Some(Err(parent_impl.def_id())) } // Parent impl contains item and makes it specializable. Some(_) => Some(Ok(())), // Parent impl doesn't mention the item. This means it's inherited from the // grandparent. In that case, if parent is a `default impl`, inherited items use the // "defaultness" from the grandparent, else they are final. None => { if tcx.impl_defaultness(parent_impl.def_id()).is_default() { None } else { Some(Err(parent_impl.def_id())) } } } }); // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the // item. This is allowed, the item isn't actually getting specialized here. let result = opt_result.unwrap_or(Ok(())); if let Err(parent_impl) = result { report_forbidden_specialization(tcx, impl_item, parent_impl); } } fn check_impl_items_against_trait<'tcx>( tcx: TyCtxt<'tcx>, impl_id: LocalDefId, impl_trait_ref: ty::TraitRef<'tcx>, ) { // If the trait reference itself is erroneous (so the compilation is going // to fail), skip checking the items here -- the `impl_item` table in `tcx` // isn't populated for such impls. if impl_trait_ref.references_error() { return; } let impl_item_refs = tcx.associated_item_def_ids(impl_id); // Negative impls are not expected to have any items match tcx.impl_polarity(impl_id) { ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {} ty::ImplPolarity::Negative => { if let [first_item_ref, ..] = impl_item_refs { let first_item_span = tcx.def_span(first_item_ref); struct_span_err!( tcx.sess, first_item_span, E0749, "negative impls cannot have any items" ) .emit(); } return; } } let trait_def = tcx.trait_def(impl_trait_ref.def_id); for &impl_item in impl_item_refs { let ty_impl_item = tcx.associated_item(impl_item); let ty_trait_item = if let Some(trait_item_id) = ty_impl_item.trait_item_def_id { tcx.associated_item(trait_item_id) } else { // Checked in `associated_item`. tcx.sess.delay_span_bug(tcx.def_span(impl_item), "missing associated item in trait"); continue; }; match ty_impl_item.kind { ty::AssocKind::Const => { let _ = tcx.compare_impl_const(( impl_item.expect_local(), ty_impl_item.trait_item_def_id.unwrap(), )); } ty::AssocKind::Fn => { compare_impl_method(tcx, ty_impl_item, ty_trait_item, impl_trait_ref); } ty::AssocKind::Type => { compare_impl_ty(tcx, ty_impl_item, ty_trait_item, impl_trait_ref); } } check_specialization_validity( tcx, trait_def, ty_trait_item, impl_id.to_def_id(), impl_item, ); } if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) { // Check for missing items from trait let mut missing_items = Vec::new(); let mut must_implement_one_of: Option<&[Ident]> = trait_def.must_implement_one_of.as_deref(); for &trait_item_id in tcx.associated_item_def_ids(impl_trait_ref.def_id) { let leaf_def = ancestors.leaf_def(tcx, trait_item_id); let is_implemented = leaf_def .as_ref() .map_or(false, |node_item| node_item.item.defaultness(tcx).has_value()); if !is_implemented && tcx.impl_defaultness(impl_id).is_final() { missing_items.push(tcx.associated_item(trait_item_id)); } // true if this item is specifically implemented in this impl let is_implemented_here = leaf_def .as_ref() .map_or(false, |node_item| !node_item.defining_node.is_from_trait()); if !is_implemented_here { let full_impl_span = tcx.hir().span_with_body(tcx.hir().local_def_id_to_hir_id(impl_id)); match tcx.eval_default_body_stability(trait_item_id, full_impl_span) { EvalResult::Deny { feature, reason, issue, .. } => default_body_is_unstable( tcx, full_impl_span, trait_item_id, feature, reason, issue, ), // Unmarked default bodies are considered stable (at least for now). EvalResult::Allow | EvalResult::Unmarked => {} } } if let Some(required_items) = &must_implement_one_of { if is_implemented_here { let trait_item = tcx.associated_item(trait_item_id); if required_items.contains(&trait_item.ident(tcx)) { must_implement_one_of = None; } } } if let Some(leaf_def) = &leaf_def && !leaf_def.is_final() && let def_id = leaf_def.item.def_id && tcx.impl_method_has_trait_impl_trait_tys(def_id) { let def_kind = tcx.def_kind(def_id); let descr = tcx.def_kind_descr(def_kind, def_id); let (msg, feature) = if tcx.asyncness(def_id).is_async() { ( format!("async {descr} in trait cannot be specialized"), sym::async_fn_in_trait, ) } else { ( format!( "{descr} with return-position `impl Trait` in trait cannot be specialized" ), sym::return_position_impl_trait_in_trait, ) }; tcx.sess .struct_span_err(tcx.def_span(def_id), msg) .note(format!( "specialization behaves in inconsistent and \ surprising ways with `#![feature({feature})]`, \ and for now is disallowed" )) .emit(); } } if !missing_items.is_empty() { let full_impl_span = tcx.hir().span_with_body(tcx.hir().local_def_id_to_hir_id(impl_id)); missing_items_err(tcx, tcx.def_span(impl_id), &missing_items, full_impl_span); } if let Some(missing_items) = must_implement_one_of { let attr_span = tcx .get_attr(impl_trait_ref.def_id, sym::rustc_must_implement_one_of) .map(|attr| attr.span); missing_items_must_implement_one_of_err( tcx, tcx.def_span(impl_id), missing_items, attr_span, ); } } } pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) { let t = tcx.type_of(def_id).subst_identity(); if let ty::Adt(def, substs) = t.kind() && def.is_struct() { let fields = &def.non_enum_variant().fields; if fields.is_empty() { struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit(); return; } let e = fields[FieldIdx::from_u32(0)].ty(tcx, substs); if !fields.iter().all(|f| f.ty(tcx, substs) == e) { struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous") .span_label(sp, "SIMD elements must have the same type") .emit(); return; } let len = if let ty::Array(_ty, c) = e.kind() { c.try_eval_target_usize(tcx, tcx.param_env(def.did())) } else { Some(fields.len() as u64) }; if let Some(len) = len { if len == 0 { struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit(); return; } else if len > MAX_SIMD_LANES { struct_span_err!( tcx.sess, sp, E0075, "SIMD vector cannot have more than {MAX_SIMD_LANES} elements", ) .emit(); return; } } // Check that we use types valid for use in the lanes of a SIMD "vector register" // These are scalar types which directly match a "machine" type // Yes: Integers, floats, "thin" pointers // No: char, "fat" pointers, compound types match e.kind() { ty::Param(_) => (), // pass struct(T, T, T, T) through, let monomorphization catch errors ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) => (), // struct(u8, u8, u8, u8) is ok ty::Array(t, _) if matches!(t.kind(), ty::Param(_)) => (), // pass struct([T; N]) through, let monomorphization catch errors ty::Array(t, _clen) if matches!( t.kind(), ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) ) => { /* struct([f32; 4]) is ok */ } _ => { struct_span_err!( tcx.sess, sp, E0077, "SIMD vector element type should be a \ primitive scalar (integer/float/pointer) type" ) .emit(); return; } } } } pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: ty::AdtDef<'_>) { let repr = def.repr(); if repr.packed() { for attr in tcx.get_attrs(def.did(), sym::repr) { for r in attr::parse_repr_attr(&tcx.sess, attr) { if let attr::ReprPacked(pack) = r && let Some(repr_pack) = repr.pack && pack as u64 != repr_pack.bytes() { struct_span_err!( tcx.sess, sp, E0634, "type has conflicting packed representation hints" ) .emit(); } } } if repr.align.is_some() { struct_span_err!( tcx.sess, sp, E0587, "type has conflicting packed and align representation hints" ) .emit(); } else { if let Some(def_spans) = check_packed_inner(tcx, def.did(), &mut vec![]) { let mut err = struct_span_err!( tcx.sess, sp, E0588, "packed type cannot transitively contain a `#[repr(align)]` type" ); err.span_note( tcx.def_span(def_spans[0].0), &format!( "`{}` has a `#[repr(align)]` attribute", tcx.item_name(def_spans[0].0) ), ); if def_spans.len() > 2 { let mut first = true; for (adt_def, span) in def_spans.iter().skip(1).rev() { let ident = tcx.item_name(*adt_def); err.span_note( *span, &if first { format!( "`{}` contains a field of type `{}`", tcx.type_of(def.did()).subst_identity(), ident ) } else { format!("...which contains a field of type `{ident}`") }, ); first = false; } } err.emit(); } } } } pub(super) fn check_packed_inner( tcx: TyCtxt<'_>, def_id: DefId, stack: &mut Vec, ) -> Option> { if let ty::Adt(def, substs) = tcx.type_of(def_id).subst_identity().kind() { if def.is_struct() || def.is_union() { if def.repr().align.is_some() { return Some(vec![(def.did(), DUMMY_SP)]); } stack.push(def_id); for field in &def.non_enum_variant().fields { if let ty::Adt(def, _) = field.ty(tcx, substs).kind() && !stack.contains(&def.did()) && let Some(mut defs) = check_packed_inner(tcx, def.did(), stack) { defs.push((def.did(), field.ident(tcx).span)); return Some(defs); } } stack.pop(); } } None } pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) { if !adt.repr().transparent() { return; } if adt.is_union() && !tcx.features().transparent_unions { feature_err( &tcx.sess.parse_sess, sym::transparent_unions, tcx.def_span(adt.did()), "transparent unions are unstable", ) .emit(); } if adt.variants().len() != 1 { bad_variant_count(tcx, adt, tcx.def_span(adt.did()), adt.did()); // Don't bother checking the fields. return; } // For each field, figure out if it's known to be a ZST and align(1), with "known" // respecting #[non_exhaustive] attributes. let field_infos = adt.all_fields().map(|field| { let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did)); let param_env = tcx.param_env(field.did); let layout = tcx.layout_of(param_env.and(ty)); // We are currently checking the type this field came from, so it must be local let span = tcx.hir().span_if_local(field.did).unwrap(); let zst = layout.map_or(false, |layout| layout.is_zst()); let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1); if !zst { return (span, zst, align1, None); } fn check_non_exhaustive<'tcx>( tcx: TyCtxt<'tcx>, t: Ty<'tcx>, ) -> ControlFlow<(&'static str, DefId, SubstsRef<'tcx>, bool)> { match t.kind() { ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)), ty::Array(ty, _) => check_non_exhaustive(tcx, *ty), ty::Adt(def, subst) => { if !def.did().is_local() { let non_exhaustive = def.is_variant_list_non_exhaustive() || def .variants() .iter() .any(ty::VariantDef::is_field_list_non_exhaustive); let has_priv = def.all_fields().any(|f| !f.vis.is_public()); if non_exhaustive || has_priv { return ControlFlow::Break(( def.descr(), def.did(), subst, non_exhaustive, )); } } def.all_fields() .map(|field| field.ty(tcx, subst)) .try_for_each(|t| check_non_exhaustive(tcx, t)) } _ => ControlFlow::Continue(()), } } (span, zst, align1, check_non_exhaustive(tcx, ty).break_value()) }); let non_zst_fields = field_infos .clone() .filter_map(|(span, zst, _align1, _non_exhaustive)| if !zst { Some(span) } else { None }); let non_zst_count = non_zst_fields.clone().count(); if non_zst_count >= 2 { bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, tcx.def_span(adt.did())); } let incompatible_zst_fields = field_infos.clone().filter(|(_, _, _, opt)| opt.is_some()).count(); let incompat = incompatible_zst_fields + non_zst_count >= 2 && non_zst_count < 2; for (span, zst, align1, non_exhaustive) in field_infos { if zst && !align1 { struct_span_err!( tcx.sess, span, E0691, "zero-sized field in transparent {} has alignment larger than 1", adt.descr(), ) .span_label(span, "has alignment larger than 1") .emit(); } if incompat && let Some((descr, def_id, substs, non_exhaustive)) = non_exhaustive { tcx.struct_span_lint_hir( REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS, tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()), span, "zero-sized fields in `repr(transparent)` cannot contain external non-exhaustive types", |lint| { let note = if non_exhaustive { "is marked with `#[non_exhaustive]`" } else { "contains private fields" }; let field_ty = tcx.def_path_str_with_substs(def_id, substs); lint .note(format!("this {descr} contains `{field_ty}`, which {note}, \ and makes it not a breaking change to become non-zero-sized in the future.")) }, ) } } } #[allow(trivial_numeric_casts)] fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) { let def = tcx.adt_def(def_id); def.destructor(tcx); // force the destructor to be evaluated if def.variants().is_empty() { if let Some(attr) = tcx.get_attrs(def_id, sym::repr).next() { struct_span_err!( tcx.sess, attr.span, E0084, "unsupported representation for zero-variant enum" ) .span_label(tcx.def_span(def_id), "zero-variant enum") .emit(); } } let repr_type_ty = def.repr().discr_type().to_ty(tcx); if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 { if !tcx.features().repr128 { feature_err( &tcx.sess.parse_sess, sym::repr128, tcx.def_span(def_id), "repr with 128-bit type is unstable", ) .emit(); } } for v in def.variants() { if let ty::VariantDiscr::Explicit(discr_def_id) = v.discr { tcx.ensure().typeck(discr_def_id.expect_local()); } } if def.repr().int.is_none() { let is_unit = |var: &ty::VariantDef| matches!(var.ctor_kind(), Some(CtorKind::Const)); let has_disr = |var: &ty::VariantDef| matches!(var.discr, ty::VariantDiscr::Explicit(_)); let has_non_units = def.variants().iter().any(|var| !is_unit(var)); let disr_units = def.variants().iter().any(|var| is_unit(&var) && has_disr(&var)); let disr_non_unit = def.variants().iter().any(|var| !is_unit(&var) && has_disr(&var)); if disr_non_unit || (disr_units && has_non_units) { let mut err = struct_span_err!( tcx.sess, tcx.def_span(def_id), E0732, "`#[repr(inttype)]` must be specified" ); err.emit(); } } detect_discriminant_duplicate(tcx, def); check_transparent(tcx, def); } /// Part of enum check. Given the discriminants of an enum, errors if two or more discriminants are equal fn detect_discriminant_duplicate<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) { // Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate. // Here `idx` refers to the order of which the discriminant appears, and its index in `vs` let report = |dis: Discr<'tcx>, idx, err: &mut Diagnostic| { let var = adt.variant(idx); // HIR for the duplicate discriminant let (span, display_discr) = match var.discr { ty::VariantDiscr::Explicit(discr_def_id) => { // In the case the discriminant is both a duplicate and overflowed, let the user know if let hir::Node::AnonConst(expr) = tcx.hir().get_by_def_id(discr_def_id.expect_local()) && let hir::ExprKind::Lit(lit) = &tcx.hir().body(expr.body).value.kind && let rustc_ast::LitKind::Int(lit_value, _int_kind) = &lit.node && *lit_value != dis.val { (tcx.def_span(discr_def_id), format!("`{dis}` (overflowed from `{lit_value}`)")) } else { // Otherwise, format the value as-is (tcx.def_span(discr_def_id), format!("`{dis}`")) } } // This should not happen. ty::VariantDiscr::Relative(0) => (tcx.def_span(var.def_id), format!("`{dis}`")), ty::VariantDiscr::Relative(distance_to_explicit) => { // At this point we know this discriminant is a duplicate, and was not explicitly // assigned by the user. Here we iterate backwards to fetch the HIR for the last // explicitly assigned discriminant, and letting the user know that this was the // increment startpoint, and how many steps from there leading to the duplicate if let Some(explicit_idx) = idx.as_u32().checked_sub(distance_to_explicit).map(VariantIdx::from_u32) { let explicit_variant = adt.variant(explicit_idx); let ve_ident = var.name; let ex_ident = explicit_variant.name; let sp = if distance_to_explicit > 1 { "variants" } else { "variant" }; err.span_label( tcx.def_span(explicit_variant.def_id), format!( "discriminant for `{ve_ident}` incremented from this startpoint \ (`{ex_ident}` + {distance_to_explicit} {sp} later \ => `{ve_ident}` = {dis})" ), ); } (tcx.def_span(var.def_id), format!("`{dis}`")) } }; err.span_label(span, format!("{display_discr} assigned here")); }; let mut discrs = adt.discriminants(tcx).collect::>(); // Here we loop through the discriminants, comparing each discriminant to another. // When a duplicate is detected, we instantiate an error and point to both // initial and duplicate value. The duplicate discriminant is then discarded by swapping // it with the last element and decrementing the `vec.len` (which is why we have to evaluate // `discrs.len()` anew every iteration, and why this could be tricky to do in a functional // style as we are mutating `discrs` on the fly). let mut i = 0; while i < discrs.len() { let var_i_idx = discrs[i].0; let mut error: Option> = None; let mut o = i + 1; while o < discrs.len() { let var_o_idx = discrs[o].0; if discrs[i].1.val == discrs[o].1.val { let err = error.get_or_insert_with(|| { let mut ret = struct_span_err!( tcx.sess, tcx.def_span(adt.did()), E0081, "discriminant value `{}` assigned more than once", discrs[i].1, ); report(discrs[i].1, var_i_idx, &mut ret); ret }); report(discrs[o].1, var_o_idx, err); // Safe to unwrap here, as we wouldn't reach this point if `discrs` was empty discrs[o] = *discrs.last().unwrap(); discrs.pop(); } else { o += 1; } } if let Some(mut e) = error { e.emit(); } i += 1; } } pub(super) fn check_type_params_are_used<'tcx>( tcx: TyCtxt<'tcx>, generics: &ty::Generics, ty: Ty<'tcx>, ) { debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty); assert_eq!(generics.parent, None); if generics.own_counts().types == 0 { return; } let mut params_used = BitSet::new_empty(generics.params.len()); if ty.references_error() { // If there is already another error, do not emit // an error for not using a type parameter. assert!(tcx.sess.has_errors().is_some()); return; } for leaf in ty.walk() { if let GenericArgKind::Type(leaf_ty) = leaf.unpack() && let ty::Param(param) = leaf_ty.kind() { debug!("found use of ty param {:?}", param); params_used.insert(param.index); } } for param in &generics.params { if !params_used.contains(param.index) && let ty::GenericParamDefKind::Type { .. } = param.kind { let span = tcx.def_span(param.def_id); struct_span_err!( tcx.sess, span, E0091, "type parameter `{}` is unused", param.name, ) .span_label(span, "unused type parameter") .emit(); } } } pub(super) fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) { let module = tcx.hir_module_items(module_def_id); for id in module.items() { check_item_type(tcx, id); } } fn async_opaque_type_cycle_error(tcx: TyCtxt<'_>, span: Span) -> ErrorGuaranteed { struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing") .span_label(span, "recursive `async fn`") .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`") .note( "consider using the `async_recursion` crate: https://crates.io/crates/async_recursion", ) .emit() } /// Emit an error for recursive opaque types. /// /// If this is a return `impl Trait`, find the item's return expressions and point at them. For /// direct recursion this is enough, but for indirect recursion also point at the last intermediary /// `impl Trait`. /// /// If all the return expressions evaluate to `!`, then we explain that the error will go away /// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder. fn opaque_type_cycle_error( tcx: TyCtxt<'_>, opaque_def_id: LocalDefId, span: Span, ) -> ErrorGuaranteed { let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type"); let mut label = false; if let Some((def_id, visitor)) = get_owner_return_paths(tcx, opaque_def_id) { let typeck_results = tcx.typeck(def_id); if visitor .returns .iter() .filter_map(|expr| typeck_results.node_type_opt(expr.hir_id)) .all(|ty| matches!(ty.kind(), ty::Never)) { let spans = visitor .returns .iter() .filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some()) .map(|expr| expr.span) .collect::>(); let span_len = spans.len(); if span_len == 1 { err.span_label(spans[0], "this returned value is of `!` type"); } else { let mut multispan: MultiSpan = spans.clone().into(); for span in spans { multispan.push_span_label(span, "this returned value is of `!` type"); } err.span_note(multispan, "these returned values have a concrete \"never\" type"); } err.help("this error will resolve once the item's body returns a concrete type"); } else { let mut seen = FxHashSet::default(); seen.insert(span); err.span_label(span, "recursive opaque type"); label = true; for (sp, ty) in visitor .returns .iter() .filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t))) .filter(|(_, ty)| !matches!(ty.kind(), ty::Never)) { #[derive(Default)] struct OpaqueTypeCollector { opaques: Vec, closures: Vec, } impl<'tcx> ty::visit::TypeVisitor> for OpaqueTypeCollector { fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow { match *t.kind() { ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => { self.opaques.push(def); ControlFlow::Continue(()) } ty::Closure(def_id, ..) | ty::Generator(def_id, ..) => { self.closures.push(def_id); t.super_visit_with(self) } _ => t.super_visit_with(self), } } } let mut visitor = OpaqueTypeCollector::default(); ty.visit_with(&mut visitor); for def_id in visitor.opaques { let ty_span = tcx.def_span(def_id); if !seen.contains(&ty_span) { let descr = if ty.is_impl_trait() { "opaque " } else { "" }; err.span_label(ty_span, &format!("returning this {descr}type `{ty}`")); seen.insert(ty_span); } err.span_label(sp, &format!("returning here with type `{ty}`")); } for closure_def_id in visitor.closures { let Some(closure_local_did) = closure_def_id.as_local() else { continue; }; let typeck_results = tcx.typeck(closure_local_did); let mut label_match = |ty: Ty<'_>, span| { for arg in ty.walk() { if let ty::GenericArgKind::Type(ty) = arg.unpack() && let ty::Alias(ty::Opaque, ty::AliasTy { def_id: captured_def_id, .. }) = *ty.kind() && captured_def_id == opaque_def_id.to_def_id() { err.span_label( span, format!( "{} captures itself here", tcx.def_descr(closure_def_id) ), ); } } }; // Label any closure upvars that capture the opaque for capture in typeck_results.closure_min_captures_flattened(closure_local_did) { label_match(capture.place.ty(), capture.get_path_span(tcx)); } // Label any generator locals that capture the opaque for interior_ty in typeck_results.generator_interior_types.as_ref().skip_binder() { label_match(interior_ty.ty, interior_ty.span); } if tcx.sess.opts.unstable_opts.drop_tracking_mir && let DefKind::Generator = tcx.def_kind(closure_def_id) { let generator_layout = tcx.mir_generator_witnesses(closure_def_id); for interior_ty in &generator_layout.field_tys { label_match(interior_ty.ty, interior_ty.source_info.span); } } } } } } if !label { err.span_label(span, "cannot resolve opaque type"); } err.emit() } pub(super) fn check_generator_obligations(tcx: TyCtxt<'_>, def_id: LocalDefId) { debug_assert!(tcx.sess.opts.unstable_opts.drop_tracking_mir); debug_assert!(matches!(tcx.def_kind(def_id), DefKind::Generator)); let typeck = tcx.typeck(def_id); let param_env = tcx.param_env(def_id); let generator_interior_predicates = &typeck.generator_interior_predicates[&def_id]; debug!(?generator_interior_predicates); let infcx = tcx .infer_ctxt() // typeck writeback gives us predicates with their regions erased. // As borrowck already has checked lifetimes, we do not need to do it again. .ignoring_regions() // Bind opaque types to `def_id` as they should have been checked by borrowck. .with_opaque_type_inference(DefiningAnchor::Bind(def_id)) .build(); let mut fulfillment_cx = >::new(infcx.tcx); for (predicate, cause) in generator_interior_predicates { let obligation = Obligation::new(tcx, cause.clone(), param_env, *predicate); fulfillment_cx.register_predicate_obligation(&infcx, obligation); } let errors = fulfillment_cx.select_all_or_error(&infcx); debug!(?errors); if !errors.is_empty() { infcx.err_ctxt().report_fulfillment_errors(&errors); } }