use crate::check::intrinsicck::InlineAsmCtxt; 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_data_structures::unord::{UnordMap, UnordSet}; use rustc_errors::{codes::*, MultiSpan}; use rustc_hir as hir; use rustc_hir::def::{CtorKind, DefKind}; use rustc_hir::Node; use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt}; use rustc_infer::traits::Obligation; use rustc_lint_defs::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS; use rustc_middle::middle::resolve_bound_vars::ResolvedArg; use rustc_middle::middle::stability::EvalResult; use rustc_middle::span_bug; use rustc_middle::ty::error::TypeErrorToStringExt; use rustc_middle::ty::fold::BottomUpFolder; use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES}; use rustc_middle::ty::util::{Discr, InspectCoroutineFields, IntTypeExt}; use rustc_middle::ty::GenericArgKind; use rustc_middle::ty::{ AdtDef, ParamEnv, RegionKind, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, }; use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVENTIONS}; use rustc_target::abi::FieldIdx; use rustc_trait_selection::error_reporting::traits::on_unimplemented::OnUnimplementedDirective; use rustc_trait_selection::error_reporting::traits::TypeErrCtxtExt as _; use rustc_trait_selection::traits; use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _; use rustc_type_ir::fold::TypeFoldable; use std::cell::LazyCell; 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_code_err!( tcx.dcx(), span, E0570, "`{abi}` is not a supported ABI for the current target", ) .emit(); } None => { tcx.node_span_lint(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| { lint.primary_message("use of calling convention not supported on this target"); }); } } // This ABI is only allowed on function pointers if abi == Abi::CCmseNonSecureCall { struct_span_code_err!( tcx.dcx(), 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); check_unnamed_fields(tcx, 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_unnamed_fields(tcx, def); } /// Check the representation of adts with unnamed fields. fn check_unnamed_fields(tcx: TyCtxt<'_>, def: ty::AdtDef<'_>) { if def.is_enum() { return; } let variant = def.non_enum_variant(); if !variant.has_unnamed_fields() { return; } if !def.is_anonymous() { let adt_kind = def.descr(); let span = tcx.def_span(def.did()); let unnamed_fields = variant .fields .iter() .filter(|f| f.is_unnamed()) .map(|f| { let span = tcx.def_span(f.did); errors::UnnamedFieldsReprFieldDefined { span } }) .collect::>(); debug_assert_ne!(unnamed_fields.len(), 0, "expect unnamed fields in this adt"); let adt_name = tcx.item_name(def.did()); if !def.repr().c() { tcx.dcx().emit_err(errors::UnnamedFieldsRepr::MissingReprC { span, adt_kind, adt_name, unnamed_fields, sugg_span: span.shrink_to_lo(), }); } } for field in variant.fields.iter().filter(|f| f.is_unnamed()) { let field_ty = tcx.type_of(field.did).instantiate_identity(); if let Some(adt) = field_ty.ty_adt_def() && !adt.is_enum() { if !adt.is_anonymous() && !adt.repr().c() { let field_ty_span = tcx.def_span(adt.did()); tcx.dcx().emit_err(errors::UnnamedFieldsRepr::FieldMissingReprC { span: tcx.def_span(field.did), field_ty_span, field_ty, field_adt_kind: adt.descr(), sugg_span: field_ty_span.shrink_to_lo(), }); } } else { tcx.dcx().emit_err(errors::InvalidUnnamedFieldTy { span: tcx.def_span(field.did) }); } } } /// 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).instantiate_identity(); if let ty::Adt(def, args) = 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 Ok(field_ty) = tcx.try_normalize_erasing_regions(param_env, field.ty(tcx, args)) else { tcx.dcx().span_delayed_bug(span, "could not normalize field type"); continue; }; 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.dcx().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.dcx() .span_delayed_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).instantiate_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.dcx().emit_err(errors::TooLargeStatic { span }); return; } // Generic statics are rejected, but we still reach this case. Err(e) => { tcx.dcx().span_delayed_bug(span, format!("{e:?}")); return; } }; if layout.abi.is_uninhabited() { tcx.node_span_lint( UNINHABITED_STATIC, tcx.local_def_id_to_hir_id(def_id), span, |lint| { lint.primary_message("static of uninhabited type"); 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<'_>, def_id: LocalDefId) { let item = tcx.hir().expect_item(def_id); let hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) = item.kind else { tcx.dcx().span_bug(item.span, "expected opaque item"); }; // 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 span = tcx.def_span(item.owner_id.def_id); if tcx.type_of(item.owner_id.def_id).instantiate_identity().references_error() { return; } if check_opaque_for_cycles(tcx, item.owner_id.def_id, span).is_err() { return; } let _ = check_opaque_meets_bounds(tcx, item.owner_id.def_id, span, origin); } /// Checks that an opaque type does not contain cycles. pub(super) fn check_opaque_for_cycles<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span, ) -> Result<(), ErrorGuaranteed> { let args = GenericArgs::identity_for_item(tcx, def_id); // First, try to look at any opaque expansion cycles, considering coroutine fields // (even though these aren't necessarily true errors). if tcx .try_expand_impl_trait_type(def_id.to_def_id(), args, InspectCoroutineFields::Yes) .is_err() { // Look for true opaque expansion cycles, but ignore coroutines. // This will give us any true errors. Coroutines are only problematic // if they cause layout computation errors. if tcx .try_expand_impl_trait_type(def_id.to_def_id(), args, InspectCoroutineFields::No) .is_err() { let reported = opaque_type_cycle_error(tcx, def_id, span); return Err(reported); } // And also look for cycle errors in the layout of coroutines. if let Err(&LayoutError::Cycle(guar)) = tcx.layout_of(tcx.param_env(def_id).and(Ty::new_opaque(tcx, def_id.to_def_id(), args))) { return Err(guar); } } 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, span: Span, origin: &hir::OpaqueTyOrigin, ) -> Result<(), ErrorGuaranteed> { let defining_use_anchor = match *origin { hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) | hir::OpaqueTyOrigin::TyAlias { parent: did, .. } => did, }; let param_env = tcx.param_env(defining_use_anchor); let infcx = tcx.infer_ctxt().with_opaque_type_inference(defining_use_anchor).build(); let ocx = ObligationCtxt::new_with_diagnostics(&infcx); let args = match *origin { hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent) | hir::OpaqueTyOrigin::TyAlias { parent, .. } => GenericArgs::identity_for_item( tcx, parent, ) .extend_to(tcx, def_id.to_def_id(), |param, _| { tcx.map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local()).into() }), }; let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), args); // `ReErased` regions appear in the "parent_args" of closures/coroutines. // We're ignoring them here and replacing them with fresh region variables. // See tests in ui/type-alias-impl-trait/closure_{parent_args,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()).instantiate(tcx, args); 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) => { // Some types may be left "stranded" if they can't be reached // from a lowered rustc_middle bound but they're mentioned in the HIR. // This will happen, e.g., when a nested opaque is inside of a non- // existent associated type, like `impl Trait`. // See . let ty_err = ty_err.to_string(tcx); let guar = tcx.dcx().span_delayed_bug( span, format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"), ); return Err(guar); } } // 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::Clause(ty::ClauseKind::WellFormed(hidden_ty.into()))); ocx.register_obligation(Obligation::new(tcx, misc_cause.clone(), 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() { let guar = infcx.err_ctxt().report_fulfillment_errors(errors); return Err(guar); } let wf_tys = ocx.assumed_wf_types_and_report_errors(param_env, defining_use_anchor)?; let implied_bounds = infcx.implied_bounds_tys(param_env, def_id, &wf_tys); let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds); ocx.resolve_regions_and_report_errors(defining_use_anchor, &outlives_env)?; if let hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) = origin { // HACK: this should also fall through to the hidden type check below, but the original // implementation had a bug where equivalent lifetimes are not identical. This caused us // to reject existing stable code that is otherwise completely fine. The real fix is to // compare the hidden types via our type equivalence/relation infra instead of doing an // identity check. let _ = infcx.take_opaque_types(); Ok(()) } else { // Check that any hidden types found during wf checking match the hidden types that `type_of` sees. for (mut key, mut ty) in infcx.take_opaque_types() { ty.hidden_type.ty = infcx.resolve_vars_if_possible(ty.hidden_type.ty); key = infcx.resolve_vars_if_possible(key); sanity_check_found_hidden_type(tcx, key, ty.hidden_type)?; } Ok(()) } } fn sanity_check_found_hidden_type<'tcx>( tcx: TyCtxt<'tcx>, key: ty::OpaqueTypeKey<'tcx>, mut ty: ty::OpaqueHiddenType<'tcx>, ) -> Result<(), ErrorGuaranteed> { if ty.ty.is_ty_var() { // Nothing was actually constrained. return Ok(()); } if let ty::Alias(ty::Opaque, alias) = ty.ty.kind() { if alias.def_id == key.def_id.to_def_id() && alias.args == key.args { // Nothing was actually constrained, this is an opaque usage that was // only discovered to be opaque after inference vars resolved. return Ok(()); } } let strip_vars = |ty: Ty<'tcx>| { ty.fold_with(&mut BottomUpFolder { tcx, ty_op: |t| t, ct_op: |c| c, lt_op: |l| match l.kind() { RegionKind::ReVar(_) => tcx.lifetimes.re_erased, _ => l, }, }) }; // Closures frequently end up containing erased lifetimes in their final representation. // These correspond to lifetime variables that never got resolved, so we patch this up here. ty.ty = strip_vars(ty.ty); // Get the hidden type. let hidden_ty = tcx.type_of(key.def_id).instantiate(tcx, key.args); let hidden_ty = strip_vars(hidden_ty); // If the hidden types differ, emit a type mismatch diagnostic. if hidden_ty == ty.ty { Ok(()) } else { let span = tcx.def_span(key.def_id); let other = ty::OpaqueHiddenType { ty: hidden_ty, span }; Err(ty.build_mismatch_error(&other, key.def_id, tcx)?.emit()) } } /// Check that the opaque's precise captures list is valid (if present). /// We check this for regular `impl Trait`s and also RPITITs, even though the latter /// are technically GATs. /// /// This function is responsible for: /// 1. Checking that all type/const params are mention in the captures list. /// 2. Checking that all lifetimes that are implicitly captured are mentioned. /// 3. Asserting that all parameters mentioned in the captures list are invariant. fn check_opaque_precise_captures<'tcx>(tcx: TyCtxt<'tcx>, opaque_def_id: LocalDefId) { let hir::OpaqueTy { bounds, .. } = *tcx.hir_node_by_def_id(opaque_def_id).expect_item().expect_opaque_ty(); let Some(precise_capturing_args) = bounds.iter().find_map(|bound| match *bound { hir::GenericBound::Use(bounds, ..) => Some(bounds), _ => None, }) else { // No precise capturing args; nothing to validate return; }; let mut expected_captures = UnordSet::default(); let mut shadowed_captures = UnordSet::default(); let mut seen_params = UnordMap::default(); let mut prev_non_lifetime_param = None; for arg in precise_capturing_args { let (hir_id, ident) = match *arg { hir::PreciseCapturingArg::Param(hir::PreciseCapturingNonLifetimeArg { hir_id, ident, .. }) => { if prev_non_lifetime_param.is_none() { prev_non_lifetime_param = Some(ident); } (hir_id, ident) } hir::PreciseCapturingArg::Lifetime(&hir::Lifetime { hir_id, ident, .. }) => { if let Some(prev_non_lifetime_param) = prev_non_lifetime_param { tcx.dcx().emit_err(errors::LifetimesMustBeFirst { lifetime_span: ident.span, name: ident.name, other_span: prev_non_lifetime_param.span, }); } (hir_id, ident) } }; let ident = ident.normalize_to_macros_2_0(); if let Some(span) = seen_params.insert(ident, ident.span) { tcx.dcx().emit_err(errors::DuplicatePreciseCapture { name: ident.name, first_span: span, second_span: ident.span, }); } match tcx.named_bound_var(hir_id) { Some(ResolvedArg::EarlyBound(def_id)) => { expected_captures.insert(def_id); // Make sure we allow capturing these lifetimes through `Self` and // `T::Assoc` projection syntax, too. These will occur when we only // see lifetimes are captured after hir-lowering -- this aligns with // the cases that were stabilized with the `impl_trait_projection` // feature -- see . if let DefKind::LifetimeParam = tcx.def_kind(def_id) && let Some(def_id) = tcx .map_opaque_lifetime_to_parent_lifetime(def_id.expect_local()) .opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id())) { shadowed_captures.insert(def_id); } } _ => { tcx.dcx().span_delayed_bug( tcx.hir().span(hir_id), "parameter should have been resolved", ); } } } let variances = tcx.variances_of(opaque_def_id); let mut def_id = Some(opaque_def_id.to_def_id()); while let Some(generics) = def_id { let generics = tcx.generics_of(generics); def_id = generics.parent; for param in &generics.own_params { if expected_captures.contains(¶m.def_id) { assert_eq!( variances[param.index as usize], ty::Invariant, "precise captured param should be invariant" ); continue; } // If a param is shadowed by a early-bound (duplicated) lifetime, then // it may or may not be captured as invariant, depending on if it shows // up through `Self` or `T::Assoc` syntax. if shadowed_captures.contains(¶m.def_id) { continue; } match param.kind { ty::GenericParamDefKind::Lifetime => { let use_span = tcx.def_span(param.def_id); let opaque_span = tcx.def_span(opaque_def_id); // Check if the lifetime param was captured but isn't named in the precise captures list. if variances[param.index as usize] == ty::Invariant { if let DefKind::OpaqueTy = tcx.def_kind(tcx.parent(param.def_id)) && let Some(def_id) = tcx .map_opaque_lifetime_to_parent_lifetime(param.def_id.expect_local()) .opt_param_def_id(tcx, tcx.parent(opaque_def_id.to_def_id())) { tcx.dcx().emit_err(errors::LifetimeNotCaptured { opaque_span, use_span, param_span: tcx.def_span(def_id), }); } else { // If the `use_span` is actually just the param itself, then we must // have not duplicated the lifetime but captured the original. // The "effective" `use_span` will be the span of the opaque itself, // and the param span will be the def span of the param. tcx.dcx().emit_err(errors::LifetimeNotCaptured { opaque_span, use_span: opaque_span, param_span: use_span, }); } continue; } } ty::GenericParamDefKind::Type { .. } => { if matches!(tcx.def_kind(param.def_id), DefKind::Trait | DefKind::TraitAlias) { // FIXME(precise_capturing): Structured suggestion for this would be useful tcx.dcx().emit_err(errors::SelfTyNotCaptured { trait_span: tcx.def_span(param.def_id), opaque_span: tcx.def_span(opaque_def_id), }); } else { // FIXME(precise_capturing): Structured suggestion for this would be useful tcx.dcx().emit_err(errors::ParamNotCaptured { param_span: tcx.def_span(param.def_id), opaque_span: tcx.def_span(opaque_def_id), kind: "type", }); } } ty::GenericParamDefKind::Const { .. } => { // FIXME(precise_capturing): Structured suggestion for this would be useful tcx.dcx().emit_err(errors::ParamNotCaptured { param_span: tcx.def_span(param.def_id), opaque_span: tcx.def_span(opaque_def_id), kind: "const", }); } } } } } fn is_enum_of_nonnullable_ptr<'tcx>( tcx: TyCtxt<'tcx>, adt_def: AdtDef<'tcx>, args: GenericArgsRef<'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, args).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).instantiate_identity().kind() { ty::RawPtr(_, _) => false, ty::Adt(adt_def, args) => !is_enum_of_nonnullable_ptr(tcx, *adt_def, *args), _ => true, } { tcx.dcx().emit_err(errors::LinkageType { span: tcx.def_span(def_id) }); } } } pub(crate) fn check_item_type(tcx: TyCtxt<'_>, def_id: LocalDefId) { match tcx.def_kind(def_id) { DefKind::Static { .. } => { tcx.ensure().typeck(def_id); maybe_check_static_with_link_section(tcx, def_id); check_static_inhabited(tcx, def_id); check_static_linkage(tcx, def_id); } DefKind::Const => { tcx.ensure().typeck(def_id); } DefKind::Enum => { check_enum(tcx, def_id); } DefKind::Fn => { if let Some(i) = tcx.intrinsic(def_id) { intrinsic::check_intrinsic_type( tcx, def_id, tcx.def_ident_span(def_id).unwrap(), i.name, Abi::Rust, ) } // Everything else is checked entirely within check_item_body } DefKind::Impl { of_trait } => { if of_trait && let Some(impl_trait_header) = tcx.impl_trait_header(def_id) { if tcx .ensure() .coherent_trait(impl_trait_header.trait_ref.instantiate_identity().def_id) .is_ok() { check_impl_items_against_trait(tcx, def_id, impl_trait_header); check_on_unimplemented(tcx, def_id); } } } DefKind::Trait => { let assoc_items = tcx.associated_items(def_id); check_on_unimplemented(tcx, def_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(); forbid_intrinsic_abi(tcx, assoc_item.ident(tcx).span, abi); } ty::AssocKind::Type if assoc_item.defaultness(tcx).has_value() => { let trait_args = GenericArgs::identity_for_item(tcx, def_id); let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds( tcx, assoc_item, assoc_item, ty::TraitRef::new_from_args(tcx, def_id.to_def_id(), trait_args), ); } _ => {} } } } DefKind::Struct => { check_struct(tcx, def_id); } DefKind::Union => { check_union(tcx, def_id); } DefKind::OpaqueTy => { check_opaque_precise_captures(tcx, def_id); let origin = tcx.opaque_type_origin(def_id); if let hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id) = origin && let hir::Node::TraitItem(trait_item) = tcx.hir_node_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, def_id); } } DefKind::TyAlias => { check_type_alias_type_params_are_used(tcx, def_id); } DefKind::ForeignMod => { let it = tcx.hir().expect_item(def_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 { intrinsic::check_intrinsic_type( tcx, item.id.owner_id.def_id, item.span, item.ident.name, abi, ); } } _ => { 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.own_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_code_err!( tcx.dcx(), item.span, E0044, "foreign items may not have {kinds} parameters", ) .with_span_label(item.span, format!("can't have {kinds} parameters")) .with_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().expect_item(def_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, def_id); } _ => {} } } pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, def_id: LocalDefId) { // an error would be reported if this fails. let _ = OnUnimplementedDirective::of_item(tcx, def_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.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 { // FIXME(effects) the associated type from effects could be specialized if !tcx.is_impl_trait_in_trait(impl_item) && !tcx.is_effects_desugared_assoc_ty(impl_item) { report_forbidden_specialization(tcx, impl_item, parent_impl); } else { tcx.dcx().delayed_bug(format!("parent item: {parent_impl:?} not marked as default")); } } } fn check_impl_items_against_trait<'tcx>( tcx: TyCtxt<'tcx>, impl_id: LocalDefId, impl_trait_header: ty::ImplTraitHeader<'tcx>, ) { let trait_ref = impl_trait_header.trait_ref.instantiate_identity(); // 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 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 impl_trait_header.polarity { 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_code_err!( tcx.dcx(), first_item_span, E0749, "negative impls cannot have any items" ) .emit(); } return; } } let trait_def = tcx.trait_def(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.dcx().span_delayed_bug(tcx.def_span(impl_item), "missing associated item in trait"); continue; }; match ty_impl_item.kind { ty::AssocKind::Const => { tcx.ensure().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, trait_ref); } ty::AssocKind::Type => { compare_impl_ty(tcx, ty_impl_item, ty_trait_item, 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(trait_ref.def_id) { let leaf_def = ancestors.leaf_def(tcx, trait_item_id); let is_implemented = leaf_def .as_ref() .is_some_and(|node_item| node_item.item.defaultness(tcx).has_value()); if !is_implemented && tcx.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().is_some_and(|node_item| !node_item.defining_node.is_from_trait()); if !is_implemented_here { let full_impl_span = tcx.hir().span_with_body(tcx.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"), "async functions in traits", ) } else { ( format!( "{descr} with return-position `impl Trait` in trait cannot be specialized" ), "return position `impl Trait` in traits", ) }; tcx.dcx() .struct_span_err(tcx.def_span(def_id), msg) .with_note(format!( "specialization behaves in inconsistent and surprising ways with \ {feature}, and for now is disallowed" )) .emit(); } } if !missing_items.is_empty() { let full_impl_span = tcx.hir().span_with_body(tcx.local_def_id_to_hir_id(impl_id)); missing_items_err(tcx, impl_id, &missing_items, full_impl_span); } if let Some(missing_items) = must_implement_one_of { let attr_span = tcx .get_attr(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).instantiate_identity(); if let ty::Adt(def, args) = t.kind() && def.is_struct() { let fields = &def.non_enum_variant().fields; if fields.is_empty() { struct_span_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit(); return; } let e = fields[FieldIdx::ZERO].ty(tcx, args); if !fields.iter().all(|f| f.ty(tcx, args) == e) { struct_span_code_err!(tcx.dcx(), sp, E0076, "SIMD vector should be homogeneous") .with_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_code_err!(tcx.dcx(), sp, E0075, "SIMD vector cannot be empty").emit(); return; } else if len > MAX_SIMD_LANES { struct_span_code_err!( tcx.dcx(), 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_code_err!( tcx.dcx(), 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 != repr_pack { struct_span_code_err!( tcx.dcx(), sp, E0634, "type has conflicting packed representation hints" ) .emit(); } } } if repr.align.is_some() { struct_span_code_err!( tcx.dcx(), 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_code_err!( tcx.dcx(), 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()).instantiate_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, args) = tcx.type_of(def_id).instantiate_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, args).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, 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 have "trivial" layout (i.e., is a 1-ZST), with // "known" respecting #[non_exhaustive] attributes. let field_infos = adt.all_fields().map(|field| { let ty = field.ty(tcx, GenericArgs::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 trivial = layout.is_ok_and(|layout| layout.is_1zst()); if !trivial { return (span, trivial, None); } // Even some 1-ZST fields are not allowed though, if they have `non_exhaustive`. fn check_non_exhaustive<'tcx>( tcx: TyCtxt<'tcx>, t: Ty<'tcx>, ) -> ControlFlow<(&'static str, DefId, GenericArgsRef<'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, args) => { 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(), args, non_exhaustive, )); } } def.all_fields() .map(|field| field.ty(tcx, args)) .try_for_each(|t| check_non_exhaustive(tcx, t)) } _ => ControlFlow::Continue(()), } } (span, trivial, check_non_exhaustive(tcx, ty).break_value()) }); let non_trivial_fields = field_infos .clone() .filter_map(|(span, trivial, _non_exhaustive)| if !trivial { Some(span) } else { None }); let non_trivial_count = non_trivial_fields.clone().count(); if non_trivial_count >= 2 { bad_non_zero_sized_fields( tcx, adt, non_trivial_count, non_trivial_fields, tcx.def_span(adt.did()), ); return; } let mut prev_non_exhaustive_1zst = false; for (span, _trivial, non_exhaustive_1zst) in field_infos { if let Some((descr, def_id, args, non_exhaustive)) = non_exhaustive_1zst { // If there are any non-trivial fields, then there can be no non-exhaustive 1-zsts. // Otherwise, it's only an issue if there's >1 non-exhaustive 1-zst. if non_trivial_count > 0 || prev_non_exhaustive_1zst { tcx.node_span_lint( REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS, tcx.local_def_id_to_hir_id(adt.did().expect_local()), span, |lint| { lint.primary_message( "zero-sized fields in `repr(transparent)` cannot \ contain external non-exhaustive types", ); let note = if non_exhaustive { "is marked with `#[non_exhaustive]`" } else { "contains private fields" }; let field_ty = tcx.def_path_str_with_args(def_id, args); 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." )); }, ) } else { prev_non_exhaustive_1zst = true; } } } } #[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_code_err!( tcx.dcx(), attr.span, E0084, "unsupported representation for zero-variant enum" ) .with_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, 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) { struct_span_code_err!( tcx.dcx(), tcx.def_span(def_id), E0732, "`#[repr(inttype)]` must be specified" ) .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 Diag<'_>| { 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_node_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_code_err!( tcx.dcx(), 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(e) = error { e.emit(); } i += 1; } } fn check_type_alias_type_params_are_used<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) { if tcx.type_alias_is_lazy(def_id) { // Since we compute the variances for lazy type aliases and already reject bivariant // parameters as unused, we can and should skip this check for lazy type aliases. return; } let generics = tcx.generics_of(def_id); if generics.own_counts().types == 0 { return; } let ty = tcx.type_of(def_id).instantiate_identity(); if ty.references_error() { // If there is already another error, do not emit an error for not using a type parameter. assert!(tcx.dcx().has_errors().is_some()); return; } // Lazily calculated because it is only needed in case of an error. let bounded_params = LazyCell::new(|| { tcx.explicit_predicates_of(def_id) .predicates .iter() .filter_map(|(predicate, span)| { let bounded_ty = match predicate.kind().skip_binder() { ty::ClauseKind::Trait(pred) => pred.trait_ref.self_ty(), ty::ClauseKind::TypeOutlives(pred) => pred.0, _ => return None, }; if let ty::Param(param) = bounded_ty.kind() { Some((param.index, span)) } else { None } }) // FIXME: This assumes that elaborated `Sized` bounds come first (which does hold at the // time of writing). This is a bit fragile since we later use the span to detect elaborated // `Sized` bounds. If they came last for example, this would break `Trait + /*elab*/Sized` // since it would overwrite the span of the user-written bound. This could be fixed by // folding the spans with `Span::to` which requires a bit of effort I think. .collect::>() }); let mut params_used = BitSet::new_empty(generics.own_params.len()); 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.own_params { if !params_used.contains(param.index) && let ty::GenericParamDefKind::Type { .. } = param.kind { let span = tcx.def_span(param.def_id); let param_name = Ident::new(param.name, span); // The corresponding predicates are post-`Sized`-elaboration. Therefore we // * check for emptiness to detect lone user-written `?Sized` bounds // * compare the param span to the pred span to detect lone user-written `Sized` bounds let has_explicit_bounds = bounded_params.is_empty() || (*bounded_params).get(¶m.index).is_some_and(|&&pred_sp| pred_sp != span); let const_param_help = (!has_explicit_bounds).then_some(()); let mut diag = tcx.dcx().create_err(errors::UnusedGenericParameter { span, param_name, param_def_kind: tcx.def_descr(param.def_id), help: errors::UnusedGenericParameterHelp::TyAlias { param_name }, usage_spans: vec![], const_param_help, }); diag.code(E0091); diag.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_code_err!(tcx.dcx(), 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>) { match *t.kind() { ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => { self.opaques.push(def); } ty::Closure(def_id, ..) | ty::Coroutine(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 coroutine locals that capture the opaque if tcx.is_coroutine(closure_def_id) && let Some(coroutine_layout) = tcx.mir_coroutine_witnesses(closure_def_id) { for interior_ty in &coroutine_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_coroutine_obligations( tcx: TyCtxt<'_>, def_id: LocalDefId, ) -> Result<(), ErrorGuaranteed> { debug_assert!(!tcx.is_typeck_child(def_id.to_def_id())); let typeck_results = tcx.typeck(def_id); let param_env = tcx.param_env(def_id); debug!(?typeck_results.coroutine_stalled_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() .with_opaque_type_inference(def_id) .build(); let ocx = ObligationCtxt::new_with_diagnostics(&infcx); for (predicate, cause) in &typeck_results.coroutine_stalled_predicates { ocx.register_obligation(Obligation::new(tcx, cause.clone(), param_env, *predicate)); } let errors = ocx.select_all_or_error(); debug!(?errors); if !errors.is_empty() { return Err(infcx.err_ctxt().report_fulfillment_errors(errors)); } // Check that any hidden types found when checking these stalled coroutine obligations // are valid. for (key, ty) in infcx.take_opaque_types() { let hidden_type = infcx.resolve_vars_if_possible(ty.hidden_type); let key = infcx.resolve_vars_if_possible(key); sanity_check_found_hidden_type(tcx, key, hidden_type)?; } Ok(()) }