1 use crate::check::intrinsicck::InlineAsmCtxt;
2 use crate::errors::LinkageType;
4 use super::compare_impl_item::check_type_bounds;
5 use super::compare_impl_item::{compare_impl_method, compare_impl_ty};
7 use rustc_attr as attr;
8 use rustc_errors::{Applicability, ErrorGuaranteed, MultiSpan};
10 use rustc_hir::def::{CtorKind, DefKind, Res};
11 use rustc_hir::def_id::{DefId, LocalDefId};
12 use rustc_hir::intravisit::Visitor;
13 use rustc_hir::{ItemKind, Node, PathSegment};
14 use rustc_infer::infer::opaque_types::ConstrainOpaqueTypeRegionVisitor;
15 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
16 use rustc_infer::infer::{DefiningAnchor, RegionVariableOrigin, TyCtxtInferExt};
17 use rustc_infer::traits::Obligation;
18 use rustc_lint::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS;
19 use rustc_middle::hir::nested_filter;
20 use rustc_middle::middle::stability::EvalResult;
21 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
22 use rustc_middle::ty::subst::GenericArgKind;
23 use rustc_middle::ty::util::{Discr, IntTypeExt};
24 use rustc_middle::ty::{self, AdtDef, ParamEnv, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable};
25 use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVENTIONS};
26 use rustc_span::symbol::sym;
27 use rustc_span::{self, Span};
28 use rustc_target::spec::abi::Abi;
29 use rustc_trait_selection::traits::error_reporting::on_unimplemented::OnUnimplementedDirective;
30 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
31 use rustc_trait_selection::traits::{self, ObligationCtxt};
33 use std::ops::ControlFlow;
35 pub fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
36 match tcx.sess.target.is_abi_supported(abi) {
43 "`{abi}` is not a supported ABI for the current target",
48 tcx.struct_span_lint_hir(
49 UNSUPPORTED_CALLING_CONVENTIONS,
52 "use of calling convention not supported on this target",
58 // This ABI is only allowed on function pointers
59 if abi == Abi::CCmseNonSecureCall {
64 "the `\"C-cmse-nonsecure-call\"` ABI is only allowed on function pointers"
70 fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
71 let def = tcx.adt_def(def_id);
72 let span = tcx.def_span(def_id);
73 def.destructor(tcx); // force the destructor to be evaluated
75 if def.repr().simd() {
76 check_simd(tcx, span, def_id);
79 check_transparent(tcx, def);
80 check_packed(tcx, span, def);
83 fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
84 let def = tcx.adt_def(def_id);
85 let span = tcx.def_span(def_id);
86 def.destructor(tcx); // force the destructor to be evaluated
87 check_transparent(tcx, def);
88 check_union_fields(tcx, span, def_id);
89 check_packed(tcx, span, def);
92 /// Check that the fields of the `union` do not need dropping.
93 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
94 let item_type = tcx.type_of(item_def_id);
95 if let ty::Adt(def, substs) = item_type.kind() {
96 assert!(def.is_union());
98 fn allowed_union_field<'tcx>(
101 param_env: ty::ParamEnv<'tcx>,
103 // We don't just accept all !needs_drop fields, due to semver concerns.
105 ty::Ref(..) => true, // references never drop (even mutable refs, which are non-Copy and hence fail the later check)
107 // allow tuples of allowed types
108 tys.iter().all(|ty| allowed_union_field(ty, tcx, param_env))
110 ty::Array(elem, _len) => {
111 // Like `Copy`, we do *not* special-case length 0.
112 allowed_union_field(*elem, tcx, param_env)
115 // Fallback case: allow `ManuallyDrop` and things that are `Copy`.
116 ty.ty_adt_def().is_some_and(|adt_def| adt_def.is_manually_drop())
117 || ty.is_copy_modulo_regions(tcx, param_env)
122 let param_env = tcx.param_env(item_def_id);
123 for field in &def.non_enum_variant().fields {
124 let field_ty = field.ty(tcx, substs);
126 if !allowed_union_field(field_ty, tcx, param_env) {
127 let (field_span, ty_span) = match tcx.hir().get_if_local(field.did) {
128 // We are currently checking the type this field came from, so it must be local.
129 Some(Node::Field(field)) => (field.span, field.ty.span),
130 _ => unreachable!("mir field has to correspond to hir field"),
136 "unions cannot contain fields that may need dropping"
139 "a type is guaranteed not to need dropping \
140 when it implements `Copy`, or when it is the special `ManuallyDrop<_>` type",
142 .multipart_suggestion_verbose(
143 "when the type does not implement `Copy`, \
144 wrap it inside a `ManuallyDrop<_>` and ensure it is manually dropped",
146 (ty_span.shrink_to_lo(), "std::mem::ManuallyDrop<".into()),
147 (ty_span.shrink_to_hi(), ">".into()),
149 Applicability::MaybeIncorrect,
153 } else if field_ty.needs_drop(tcx, param_env) {
154 // This should never happen. But we can get here e.g. in case of name resolution errors.
155 tcx.sess.delay_span_bug(span, "we should never accept maybe-dropping union fields");
159 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind());
164 /// Check that a `static` is inhabited.
165 fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
166 // Make sure statics are inhabited.
167 // Other parts of the compiler assume that there are no uninhabited places. In principle it
168 // would be enough to check this for `extern` statics, as statics with an initializer will
169 // have UB during initialization if they are uninhabited, but there also seems to be no good
170 // reason to allow any statics to be uninhabited.
171 let ty = tcx.type_of(def_id);
172 let span = tcx.def_span(def_id);
173 let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
175 // Foreign statics that overflow their allowed size should emit an error
176 Err(LayoutError::SizeOverflow(_))
178 let node = tcx.hir().get_by_def_id(def_id);
181 hir::Node::ForeignItem(hir::ForeignItem {
182 kind: hir::ForeignItemKind::Static(..),
189 .struct_span_err(span, "extern static is too large for the current architecture")
193 // Generic statics are rejected, but we still reach this case.
195 tcx.sess.delay_span_bug(span, &e.to_string());
199 if layout.abi.is_uninhabited() {
200 tcx.struct_span_lint_hir(
202 tcx.hir().local_def_id_to_hir_id(def_id),
204 "static of uninhabited type",
207 .note("uninhabited statics cannot be initialized, and any access would be an immediate error")
213 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
214 /// projections that would result in "inheriting lifetimes".
215 fn check_opaque(tcx: TyCtxt<'_>, id: hir::ItemId) {
216 let item = tcx.hir().item(id);
217 let hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) = item.kind else {
218 tcx.sess.delay_span_bug(tcx.hir().span(id.hir_id()), "expected opaque item");
222 // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
223 // `async-std` (and `pub async fn` in general).
224 // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
225 // See https://github.com/rust-lang/rust/issues/75100
226 if tcx.sess.opts.actually_rustdoc {
230 let substs = InternalSubsts::identity_for_item(tcx, item.owner_id.to_def_id());
231 let span = tcx.def_span(item.owner_id.def_id);
233 if !tcx.features().impl_trait_projections {
234 check_opaque_for_inheriting_lifetimes(tcx, item.owner_id.def_id, span);
236 if tcx.type_of(item.owner_id.def_id).references_error() {
239 if check_opaque_for_cycles(tcx, item.owner_id.def_id, substs, span, &origin).is_err() {
242 check_opaque_meets_bounds(tcx, item.owner_id.def_id, substs, span, &origin);
245 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
246 /// in "inheriting lifetimes".
247 #[instrument(level = "debug", skip(tcx, span))]
248 pub(super) fn check_opaque_for_inheriting_lifetimes(
253 let item = tcx.hir().expect_item(def_id);
254 debug!(?item, ?span);
256 struct ProhibitOpaqueVisitor<'tcx> {
258 opaque_identity_ty: Ty<'tcx>,
260 references_parent_regions: bool,
261 selftys: Vec<(Span, Option<String>)>,
264 impl<'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
265 type BreakTy = Ty<'tcx>;
267 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
268 debug!(?t, "root_visit_ty");
269 if t == self.opaque_identity_ty {
270 ControlFlow::CONTINUE
272 t.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
275 if let ty::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = *region
276 && index < self.parent_count
278 self.references_parent_regions= true;
282 if self.references_parent_regions {
283 ControlFlow::Break(t)
285 ControlFlow::CONTINUE
291 impl<'tcx> Visitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
292 type NestedFilter = nested_filter::OnlyBodies;
294 fn nested_visit_map(&mut self) -> Self::Map {
298 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
300 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
301 [PathSegment { res: Res::SelfTyParam { .. }, .. }] => {
302 let impl_ty_name = None;
303 self.selftys.push((path.span, impl_ty_name));
305 [PathSegment { res: Res::SelfTyAlias { alias_to: def_id, .. }, .. }] => {
306 let impl_ty_name = Some(self.tcx.def_path_str(*def_id));
307 self.selftys.push((path.span, impl_ty_name));
313 hir::intravisit::walk_ty(self, arg);
317 if let ItemKind::OpaqueTy(hir::OpaqueTy {
318 origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
323 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
324 let opaque_identity_ty = if in_trait {
325 tcx.mk_projection(def_id.to_def_id(), substs)
327 tcx.mk_opaque(def_id.to_def_id(), substs)
329 let mut visitor = ProhibitOpaqueVisitor {
331 parent_count: tcx.generics_of(def_id).parent_count as u32,
332 references_parent_regions: false,
336 let prohibit_opaque = tcx
337 .explicit_item_bounds(def_id)
339 .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
341 if let Some(ty) = prohibit_opaque.break_value() {
342 visitor.visit_item(&item);
343 let is_async = match item.kind {
344 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
345 matches!(origin, hir::OpaqueTyOrigin::AsyncFn(..))
350 let mut err = feature_err(
351 &tcx.sess.parse_sess,
352 sym::impl_trait_projections,
355 "`{}` return type cannot contain a projection or `Self` that references \
356 lifetimes from a parent scope",
357 if is_async { "async fn" } else { "impl Trait" },
360 for (span, name) in visitor.selftys {
363 "consider spelling out the type instead",
364 name.unwrap_or_else(|| format!("{:?}", ty)),
365 Applicability::MaybeIncorrect,
373 /// Checks that an opaque type does not contain cycles.
374 pub(super) fn check_opaque_for_cycles<'tcx>(
377 substs: SubstsRef<'tcx>,
379 origin: &hir::OpaqueTyOrigin,
380 ) -> Result<(), ErrorGuaranteed> {
381 if tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs).is_err() {
382 let reported = match origin {
383 hir::OpaqueTyOrigin::AsyncFn(..) => async_opaque_type_cycle_error(tcx, span),
384 _ => opaque_type_cycle_error(tcx, def_id, span),
392 /// Check that the concrete type behind `impl Trait` actually implements `Trait`.
394 /// This is mostly checked at the places that specify the opaque type, but we
395 /// check those cases in the `param_env` of that function, which may have
396 /// bounds not on this opaque type:
398 /// ```ignore (illustrative)
399 /// type X<T> = impl Clone;
400 /// fn f<T: Clone>(t: T) -> X<T> {
405 /// Without this check the above code is incorrectly accepted: we would ICE if
406 /// some tried, for example, to clone an `Option<X<&mut ()>>`.
407 #[instrument(level = "debug", skip(tcx))]
408 fn check_opaque_meets_bounds<'tcx>(
411 substs: SubstsRef<'tcx>,
413 origin: &hir::OpaqueTyOrigin,
415 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
416 let defining_use_anchor = match *origin {
417 hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) => did,
418 hir::OpaqueTyOrigin::TyAlias => def_id,
420 let param_env = tcx.param_env(defining_use_anchor);
424 .with_opaque_type_inference(DefiningAnchor::Bind(defining_use_anchor))
426 let ocx = ObligationCtxt::new(&infcx);
427 let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
429 // `ReErased` regions appear in the "parent_substs" of closures/generators.
430 // We're ignoring them here and replacing them with fresh region variables.
431 // See tests in ui/type-alias-impl-trait/closure_{parent_substs,wf_outlives}.rs.
433 // FIXME: Consider wrapping the hidden type in an existential `Binder` and instantiating it
434 // here rather than using ReErased.
435 let hidden_ty = tcx.bound_type_of(def_id.to_def_id()).subst(tcx, substs);
436 let hidden_ty = tcx.fold_regions(hidden_ty, |re, _dbi| match re.kind() {
437 ty::ReErased => infcx.next_region_var(RegionVariableOrigin::MiscVariable(span)),
441 let misc_cause = traits::ObligationCause::misc(span, hir_id);
443 match ocx.eq(&misc_cause, param_env, opaque_ty, hidden_ty) {
446 tcx.sess.delay_span_bug(
448 &format!("could not unify `{hidden_ty}` with revealed type:\n{ty_err}"),
453 // Additionally require the hidden type to be well-formed with only the generics of the opaque type.
454 // Defining use functions may have more bounds than the opaque type, which is ok, as long as the
455 // hidden type is well formed even without those bounds.
456 let predicate = ty::Binder::dummy(ty::PredicateKind::WellFormed(hidden_ty.into()));
457 ocx.register_obligation(Obligation::new(tcx, misc_cause, param_env, predicate));
459 // Check that all obligations are satisfied by the implementation's
461 let errors = ocx.select_all_or_error();
462 if !errors.is_empty() {
463 infcx.err_ctxt().report_fulfillment_errors(&errors, None);
466 // Checked when type checking the function containing them.
467 hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => {}
468 // Can have different predicates to their defining use
469 hir::OpaqueTyOrigin::TyAlias => {
470 let outlives_environment = OutlivesEnvironment::new(param_env);
471 let _ = infcx.err_ctxt().check_region_obligations_and_report_errors(
473 &outlives_environment,
477 // Clean up after ourselves
478 let _ = infcx.take_opaque_types();
481 fn is_enum_of_nonnullable_ptr<'tcx>(
483 adt_def: AdtDef<'tcx>,
484 substs: SubstsRef<'tcx>,
486 if adt_def.repr().inhibit_enum_layout_opt() {
490 let [var_one, var_two] = &adt_def.variants().raw[..] else {
493 let (([], [field]) | ([field], [])) = (&var_one.fields[..], &var_two.fields[..]) else {
496 matches!(field.ty(tcx, substs).kind(), ty::FnPtr(..) | ty::Ref(..))
499 fn check_static_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) {
500 if tcx.codegen_fn_attrs(def_id).import_linkage.is_some() {
501 if match tcx.type_of(def_id).kind() {
502 ty::RawPtr(_) => false,
503 ty::Adt(adt_def, substs) => !is_enum_of_nonnullable_ptr(tcx, *adt_def, *substs),
506 tcx.sess.emit_err(LinkageType { span: tcx.def_span(def_id) });
511 fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
513 "check_item_type(it.def_id={:?}, it.name={})",
515 tcx.def_path_str(id.owner_id.to_def_id())
517 let _indenter = indenter();
518 match tcx.def_kind(id.owner_id) {
519 DefKind::Static(..) => {
520 tcx.ensure().typeck(id.owner_id.def_id);
521 maybe_check_static_with_link_section(tcx, id.owner_id.def_id);
522 check_static_inhabited(tcx, id.owner_id.def_id);
523 check_static_linkage(tcx, id.owner_id.def_id);
526 tcx.ensure().typeck(id.owner_id.def_id);
529 check_enum(tcx, id.owner_id.def_id);
531 DefKind::Fn => {} // entirely within check_item_body
533 let it = tcx.hir().item(id);
534 let hir::ItemKind::Impl(ref impl_) = it.kind else {
537 debug!("ItemKind::Impl {} with id {:?}", it.ident, it.owner_id);
538 if let Some(impl_trait_ref) = tcx.impl_trait_ref(it.owner_id) {
539 check_impl_items_against_trait(
543 impl_trait_ref.subst_identity(),
546 check_on_unimplemented(tcx, it);
550 let it = tcx.hir().item(id);
551 let hir::ItemKind::Trait(_, _, _, _, ref items) = it.kind else {
554 check_on_unimplemented(tcx, it);
556 for item in items.iter() {
557 let item = tcx.hir().trait_item(item.id);
559 hir::TraitItemKind::Fn(ref sig, _) => {
560 let abi = sig.header.abi;
561 fn_maybe_err(tcx, item.ident.span, abi);
563 hir::TraitItemKind::Type(.., Some(default)) => {
564 let assoc_item = tcx.associated_item(item.owner_id);
566 InternalSubsts::identity_for_item(tcx, it.owner_id.to_def_id());
567 let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds(
572 tcx.mk_trait_ref(it.owner_id.to_def_id(), trait_substs),
580 check_struct(tcx, id.owner_id.def_id);
583 check_union(tcx, id.owner_id.def_id);
585 DefKind::OpaqueTy => {
586 check_opaque(tcx, id);
588 DefKind::ImplTraitPlaceholder => {
589 let parent = tcx.impl_trait_in_trait_parent(id.owner_id.to_def_id());
590 // Only check the validity of this opaque type if the function has a default body
591 if let hir::Node::TraitItem(hir::TraitItem {
592 kind: hir::TraitItemKind::Fn(_, hir::TraitFn::Provided(_)),
594 }) = tcx.hir().get_by_def_id(parent.expect_local())
596 check_opaque(tcx, id);
599 DefKind::TyAlias => {
600 let pty_ty = tcx.type_of(id.owner_id);
601 let generics = tcx.generics_of(id.owner_id);
602 check_type_params_are_used(tcx, &generics, pty_ty);
604 DefKind::ForeignMod => {
605 let it = tcx.hir().item(id);
606 let hir::ItemKind::ForeignMod { abi, items } = it.kind else {
609 check_abi(tcx, it.hir_id(), it.span, abi);
611 if abi == Abi::RustIntrinsic {
613 let item = tcx.hir().foreign_item(item.id);
614 intrinsic::check_intrinsic_type(tcx, item);
616 } else if abi == Abi::PlatformIntrinsic {
618 let item = tcx.hir().foreign_item(item.id);
619 intrinsic::check_platform_intrinsic_type(tcx, item);
623 let def_id = item.id.owner_id.def_id;
624 let generics = tcx.generics_of(def_id);
625 let own_counts = generics.own_counts();
626 if generics.params.len() - own_counts.lifetimes != 0 {
627 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
628 (_, 0) => ("type", "types", Some("u32")),
629 // We don't specify an example value, because we can't generate
630 // a valid value for any type.
631 (0, _) => ("const", "consts", None),
632 _ => ("type or const", "types or consts", None),
638 "foreign items may not have {kinds} parameters",
640 .span_label(item.span, &format!("can't have {kinds} parameters"))
642 // FIXME: once we start storing spans for type arguments, turn this
643 // into a suggestion.
645 "replace the {} parameters with concrete {}{}",
648 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
654 let item = tcx.hir().foreign_item(item.id);
656 hir::ForeignItemKind::Fn(ref fn_decl, _, _) => {
657 require_c_abi_if_c_variadic(tcx, fn_decl, abi, item.span);
659 hir::ForeignItemKind::Static(..) => {
660 check_static_inhabited(tcx, def_id);
661 check_static_linkage(tcx, def_id);
668 DefKind::GlobalAsm => {
669 let it = tcx.hir().item(id);
670 let hir::ItemKind::GlobalAsm(asm) = it.kind else { span_bug!(it.span, "DefKind::GlobalAsm but got {:#?}", it) };
671 InlineAsmCtxt::new_global_asm(tcx).check_asm(asm, id.hir_id());
677 pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, item: &hir::Item<'_>) {
678 // an error would be reported if this fails.
679 let _ = OnUnimplementedDirective::of_item(tcx, item.owner_id.to_def_id());
682 pub(super) fn check_specialization_validity<'tcx>(
684 trait_def: &ty::TraitDef,
685 trait_item: &ty::AssocItem,
687 impl_item: &hir::ImplItemRef,
689 let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) else { return };
690 let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| {
691 if parent.is_from_trait() {
694 Some((parent, parent.item(tcx, trait_item.def_id)))
698 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
700 // Parent impl exists, and contains the parent item we're trying to specialize, but
701 // doesn't mark it `default`.
702 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
703 Some(Err(parent_impl.def_id()))
706 // Parent impl contains item and makes it specializable.
707 Some(_) => Some(Ok(())),
709 // Parent impl doesn't mention the item. This means it's inherited from the
710 // grandparent. In that case, if parent is a `default impl`, inherited items use the
711 // "defaultness" from the grandparent, else they are final.
713 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
716 Some(Err(parent_impl.def_id()))
722 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
723 // item. This is allowed, the item isn't actually getting specialized here.
724 let result = opt_result.unwrap_or(Ok(()));
726 if let Err(parent_impl) = result {
727 report_forbidden_specialization(tcx, impl_item, parent_impl);
731 fn check_impl_items_against_trait<'tcx>(
733 full_impl_span: Span,
735 impl_trait_ref: ty::TraitRef<'tcx>,
736 impl_item_refs: &[hir::ImplItemRef],
738 // If the trait reference itself is erroneous (so the compilation is going
739 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
740 // isn't populated for such impls.
741 if impl_trait_ref.references_error() {
745 // Negative impls are not expected to have any items
746 match tcx.impl_polarity(impl_id) {
747 ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
748 ty::ImplPolarity::Negative => {
749 if let [first_item_ref, ..] = impl_item_refs {
750 let first_item_span = tcx.hir().impl_item(first_item_ref.id).span;
755 "negative impls cannot have any items"
763 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
765 for impl_item in impl_item_refs {
766 let ty_impl_item = tcx.associated_item(impl_item.id.owner_id);
767 let ty_trait_item = if let Some(trait_item_id) = ty_impl_item.trait_item_def_id {
768 tcx.associated_item(trait_item_id)
770 // Checked in `associated_item`.
771 tcx.sess.delay_span_bug(impl_item.span, "missing associated item in trait");
774 let impl_item_full = tcx.hir().impl_item(impl_item.id);
775 match impl_item_full.kind {
776 hir::ImplItemKind::Const(..) => {
777 let _ = tcx.compare_impl_const((
778 impl_item.id.owner_id.def_id,
779 ty_impl_item.trait_item_def_id.unwrap(),
782 hir::ImplItemKind::Fn(..) => {
783 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
792 hir::ImplItemKind::Type(impl_ty) => {
793 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
805 check_specialization_validity(
814 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) {
815 // Check for missing items from trait
816 let mut missing_items = Vec::new();
818 let mut must_implement_one_of: Option<&[Ident]> =
819 trait_def.must_implement_one_of.as_deref();
821 for &trait_item_id in tcx.associated_item_def_ids(impl_trait_ref.def_id) {
822 let is_implemented = ancestors
823 .leaf_def(tcx, trait_item_id)
824 .map_or(false, |node_item| node_item.item.defaultness(tcx).has_value());
826 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
827 missing_items.push(tcx.associated_item(trait_item_id));
830 // true if this item is specifically implemented in this impl
831 let is_implemented_here = ancestors
832 .leaf_def(tcx, trait_item_id)
833 .map_or(false, |node_item| !node_item.defining_node.is_from_trait());
835 if !is_implemented_here {
836 match tcx.eval_default_body_stability(trait_item_id, full_impl_span) {
837 EvalResult::Deny { feature, reason, issue, .. } => default_body_is_unstable(
846 // Unmarked default bodies are considered stable (at least for now).
847 EvalResult::Allow | EvalResult::Unmarked => {}
851 if let Some(required_items) = &must_implement_one_of {
852 if is_implemented_here {
853 let trait_item = tcx.associated_item(trait_item_id);
854 if required_items.contains(&trait_item.ident(tcx)) {
855 must_implement_one_of = None;
861 if !missing_items.is_empty() {
862 missing_items_err(tcx, tcx.def_span(impl_id), &missing_items, full_impl_span);
865 if let Some(missing_items) = must_implement_one_of {
867 .get_attr(impl_trait_ref.def_id, sym::rustc_must_implement_one_of)
868 .map(|attr| attr.span);
870 missing_items_must_implement_one_of_err(
872 tcx.def_span(impl_id),
880 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
881 let t = tcx.type_of(def_id);
882 if let ty::Adt(def, substs) = t.kind()
885 let fields = &def.non_enum_variant().fields;
886 if fields.is_empty() {
887 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
890 let e = fields[0].ty(tcx, substs);
891 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
892 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
893 .span_label(sp, "SIMD elements must have the same type")
898 let len = if let ty::Array(_ty, c) = e.kind() {
899 c.try_eval_usize(tcx, tcx.param_env(def.did()))
901 Some(fields.len() as u64)
903 if let Some(len) = len {
905 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
907 } else if len > MAX_SIMD_LANES {
912 "SIMD vector cannot have more than {MAX_SIMD_LANES} elements",
919 // Check that we use types valid for use in the lanes of a SIMD "vector register"
920 // These are scalar types which directly match a "machine" type
921 // Yes: Integers, floats, "thin" pointers
922 // No: char, "fat" pointers, compound types
924 ty::Param(_) => (), // pass struct<T>(T, T, T, T) through, let monomorphization catch errors
925 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) => (), // struct(u8, u8, u8, u8) is ok
926 ty::Array(t, _) if matches!(t.kind(), ty::Param(_)) => (), // pass struct<T>([T; N]) through, let monomorphization catch errors
930 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_)
932 { /* struct([f32; 4]) is ok */ }
938 "SIMD vector element type should be a \
939 primitive scalar (integer/float/pointer) type"
948 pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: ty::AdtDef<'_>) {
949 let repr = def.repr();
951 for attr in tcx.get_attrs(def.did(), sym::repr) {
952 for r in attr::parse_repr_attr(&tcx.sess, attr) {
953 if let attr::ReprPacked(pack) = r
954 && let Some(repr_pack) = repr.pack
955 && pack as u64 != repr_pack.bytes()
961 "type has conflicting packed representation hints"
967 if repr.align.is_some() {
972 "type has conflicting packed and align representation hints"
976 if let Some(def_spans) = check_packed_inner(tcx, def.did(), &mut vec![]) {
977 let mut err = struct_span_err!(
981 "packed type cannot transitively contain a `#[repr(align)]` type"
985 tcx.def_span(def_spans[0].0),
987 "`{}` has a `#[repr(align)]` attribute",
988 tcx.item_name(def_spans[0].0)
992 if def_spans.len() > 2 {
993 let mut first = true;
994 for (adt_def, span) in def_spans.iter().skip(1).rev() {
995 let ident = tcx.item_name(*adt_def);
1000 "`{}` contains a field of type `{}`",
1001 tcx.type_of(def.did()),
1005 format!("...which contains a field of type `{ident}`")
1018 pub(super) fn check_packed_inner(
1021 stack: &mut Vec<DefId>,
1022 ) -> Option<Vec<(DefId, Span)>> {
1023 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind() {
1024 if def.is_struct() || def.is_union() {
1025 if def.repr().align.is_some() {
1026 return Some(vec![(def.did(), DUMMY_SP)]);
1030 for field in &def.non_enum_variant().fields {
1031 if let ty::Adt(def, _) = field.ty(tcx, substs).kind()
1032 && !stack.contains(&def.did())
1033 && let Some(mut defs) = check_packed_inner(tcx, def.did(), stack)
1035 defs.push((def.did(), field.ident(tcx).span));
1046 pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) {
1047 if !adt.repr().transparent() {
1051 if adt.is_union() && !tcx.features().transparent_unions {
1053 &tcx.sess.parse_sess,
1054 sym::transparent_unions,
1055 tcx.def_span(adt.did()),
1056 "transparent unions are unstable",
1061 if adt.variants().len() != 1 {
1062 bad_variant_count(tcx, adt, tcx.def_span(adt.did()), adt.did());
1063 // Don't bother checking the fields.
1067 // For each field, figure out if it's known to be a ZST and align(1), with "known"
1068 // respecting #[non_exhaustive] attributes.
1069 let field_infos = adt.all_fields().map(|field| {
1070 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1071 let param_env = tcx.param_env(field.did);
1072 let layout = tcx.layout_of(param_env.and(ty));
1073 // We are currently checking the type this field came from, so it must be local
1074 let span = tcx.hir().span_if_local(field.did).unwrap();
1075 let zst = layout.map_or(false, |layout| layout.is_zst());
1076 let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1);
1078 return (span, zst, align1, None);
1081 fn check_non_exhaustive<'tcx>(
1084 ) -> ControlFlow<(&'static str, DefId, SubstsRef<'tcx>, bool)> {
1086 ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)),
1087 ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
1088 ty::Adt(def, subst) => {
1089 if !def.did().is_local() {
1090 let non_exhaustive = def.is_variant_list_non_exhaustive()
1094 .any(ty::VariantDef::is_field_list_non_exhaustive);
1095 let has_priv = def.all_fields().any(|f| !f.vis.is_public());
1096 if non_exhaustive || has_priv {
1097 return ControlFlow::Break((
1106 .map(|field| field.ty(tcx, subst))
1107 .try_for_each(|t| check_non_exhaustive(tcx, t))
1109 _ => ControlFlow::Continue(()),
1113 (span, zst, align1, check_non_exhaustive(tcx, ty).break_value())
1116 let non_zst_fields = field_infos
1118 .filter_map(|(span, zst, _align1, _non_exhaustive)| if !zst { Some(span) } else { None });
1119 let non_zst_count = non_zst_fields.clone().count();
1120 if non_zst_count >= 2 {
1121 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, tcx.def_span(adt.did()));
1123 let incompatible_zst_fields =
1124 field_infos.clone().filter(|(_, _, _, opt)| opt.is_some()).count();
1125 let incompat = incompatible_zst_fields + non_zst_count >= 2 && non_zst_count < 2;
1126 for (span, zst, align1, non_exhaustive) in field_infos {
1132 "zero-sized field in transparent {} has alignment larger than 1",
1135 .span_label(span, "has alignment larger than 1")
1138 if incompat && let Some((descr, def_id, substs, non_exhaustive)) = non_exhaustive {
1139 tcx.struct_span_lint_hir(
1140 REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
1141 tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()),
1143 "zero-sized fields in `repr(transparent)` cannot contain external non-exhaustive types",
1145 let note = if non_exhaustive {
1146 "is marked with `#[non_exhaustive]`"
1148 "contains private fields"
1150 let field_ty = tcx.def_path_str_with_substs(def_id, substs);
1152 .note(format!("this {descr} contains `{field_ty}`, which {note}, \
1153 and makes it not a breaking change to become non-zero-sized in the future."))
1160 #[allow(trivial_numeric_casts)]
1161 fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1162 let def = tcx.adt_def(def_id);
1163 def.destructor(tcx); // force the destructor to be evaluated
1165 if def.variants().is_empty() {
1166 if let Some(attr) = tcx.get_attrs(def_id.to_def_id(), sym::repr).next() {
1171 "unsupported representation for zero-variant enum"
1173 .span_label(tcx.def_span(def_id), "zero-variant enum")
1178 let repr_type_ty = def.repr().discr_type().to_ty(tcx);
1179 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1180 if !tcx.features().repr128 {
1182 &tcx.sess.parse_sess,
1184 tcx.def_span(def_id),
1185 "repr with 128-bit type is unstable",
1191 for v in def.variants() {
1192 if let ty::VariantDiscr::Explicit(discr_def_id) = v.discr {
1193 tcx.ensure().typeck(discr_def_id.expect_local());
1197 if def.repr().int.is_none() {
1198 let is_unit = |var: &ty::VariantDef| matches!(var.ctor_kind(), Some(CtorKind::Const));
1199 let has_disr = |var: &ty::VariantDef| matches!(var.discr, ty::VariantDiscr::Explicit(_));
1201 let has_non_units = def.variants().iter().any(|var| !is_unit(var));
1202 let disr_units = def.variants().iter().any(|var| is_unit(&var) && has_disr(&var));
1203 let disr_non_unit = def.variants().iter().any(|var| !is_unit(&var) && has_disr(&var));
1205 if disr_non_unit || (disr_units && has_non_units) {
1206 let mut err = struct_span_err!(
1208 tcx.def_span(def_id),
1210 "`#[repr(inttype)]` must be specified"
1216 detect_discriminant_duplicate(tcx, def);
1217 check_transparent(tcx, def);
1220 /// Part of enum check. Given the discriminants of an enum, errors if two or more discriminants are equal
1221 fn detect_discriminant_duplicate<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>) {
1222 // Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate.
1223 // Here `idx` refers to the order of which the discriminant appears, and its index in `vs`
1224 let report = |dis: Discr<'tcx>, idx, err: &mut Diagnostic| {
1225 let var = adt.variant(idx); // HIR for the duplicate discriminant
1226 let (span, display_discr) = match var.discr {
1227 ty::VariantDiscr::Explicit(discr_def_id) => {
1228 // In the case the discriminant is both a duplicate and overflowed, let the user know
1229 if let hir::Node::AnonConst(expr) = tcx.hir().get_by_def_id(discr_def_id.expect_local())
1230 && let hir::ExprKind::Lit(lit) = &tcx.hir().body(expr.body).value.kind
1231 && let rustc_ast::LitKind::Int(lit_value, _int_kind) = &lit.node
1232 && *lit_value != dis.val
1234 (tcx.def_span(discr_def_id), format!("`{dis}` (overflowed from `{lit_value}`)"))
1236 // Otherwise, format the value as-is
1237 (tcx.def_span(discr_def_id), format!("`{dis}`"))
1240 // This should not happen.
1241 ty::VariantDiscr::Relative(0) => (tcx.def_span(var.def_id), format!("`{dis}`")),
1242 ty::VariantDiscr::Relative(distance_to_explicit) => {
1243 // At this point we know this discriminant is a duplicate, and was not explicitly
1244 // assigned by the user. Here we iterate backwards to fetch the HIR for the last
1245 // explicitly assigned discriminant, and letting the user know that this was the
1246 // increment startpoint, and how many steps from there leading to the duplicate
1247 if let Some(explicit_idx) =
1248 idx.as_u32().checked_sub(distance_to_explicit).map(VariantIdx::from_u32)
1250 let explicit_variant = adt.variant(explicit_idx);
1251 let ve_ident = var.name;
1252 let ex_ident = explicit_variant.name;
1253 let sp = if distance_to_explicit > 1 { "variants" } else { "variant" };
1256 tcx.def_span(explicit_variant.def_id),
1258 "discriminant for `{ve_ident}` incremented from this startpoint \
1259 (`{ex_ident}` + {distance_to_explicit} {sp} later \
1260 => `{ve_ident}` = {dis})"
1265 (tcx.def_span(var.def_id), format!("`{dis}`"))
1269 err.span_label(span, format!("{display_discr} assigned here"));
1272 let mut discrs = adt.discriminants(tcx).collect::<Vec<_>>();
1274 // Here we loop through the discriminants, comparing each discriminant to another.
1275 // When a duplicate is detected, we instantiate an error and point to both
1276 // initial and duplicate value. The duplicate discriminant is then discarded by swapping
1277 // it with the last element and decrementing the `vec.len` (which is why we have to evaluate
1278 // `discrs.len()` anew every iteration, and why this could be tricky to do in a functional
1279 // style as we are mutating `discrs` on the fly).
1281 while i < discrs.len() {
1282 let var_i_idx = discrs[i].0;
1283 let mut error: Option<DiagnosticBuilder<'_, _>> = None;
1286 while o < discrs.len() {
1287 let var_o_idx = discrs[o].0;
1289 if discrs[i].1.val == discrs[o].1.val {
1290 let err = error.get_or_insert_with(|| {
1291 let mut ret = struct_span_err!(
1293 tcx.def_span(adt.did()),
1295 "discriminant value `{}` assigned more than once",
1299 report(discrs[i].1, var_i_idx, &mut ret);
1304 report(discrs[o].1, var_o_idx, err);
1306 // Safe to unwrap here, as we wouldn't reach this point if `discrs` was empty
1307 discrs[o] = *discrs.last().unwrap();
1314 if let Some(mut e) = error {
1322 pub(super) fn check_type_params_are_used<'tcx>(
1324 generics: &ty::Generics,
1327 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
1329 assert_eq!(generics.parent, None);
1331 if generics.own_counts().types == 0 {
1335 let mut params_used = BitSet::new_empty(generics.params.len());
1337 if ty.references_error() {
1338 // If there is already another error, do not emit
1339 // an error for not using a type parameter.
1340 assert!(tcx.sess.has_errors().is_some());
1344 for leaf in ty.walk() {
1345 if let GenericArgKind::Type(leaf_ty) = leaf.unpack()
1346 && let ty::Param(param) = leaf_ty.kind()
1348 debug!("found use of ty param {:?}", param);
1349 params_used.insert(param.index);
1353 for param in &generics.params {
1354 if !params_used.contains(param.index)
1355 && let ty::GenericParamDefKind::Type { .. } = param.kind
1357 let span = tcx.def_span(param.def_id);
1362 "type parameter `{}` is unused",
1365 .span_label(span, "unused type parameter")
1371 pub(super) fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
1372 let module = tcx.hir_module_items(module_def_id);
1373 for id in module.items() {
1374 check_item_type(tcx, id);
1378 fn async_opaque_type_cycle_error(tcx: TyCtxt<'_>, span: Span) -> ErrorGuaranteed {
1379 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
1380 .span_label(span, "recursive `async fn`")
1381 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1383 "consider using the `async_recursion` crate: https://crates.io/crates/async_recursion",
1388 /// Emit an error for recursive opaque types.
1390 /// If this is a return `impl Trait`, find the item's return expressions and point at them. For
1391 /// direct recursion this is enough, but for indirect recursion also point at the last intermediary
1394 /// If all the return expressions evaluate to `!`, then we explain that the error will go away
1395 /// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
1396 fn opaque_type_cycle_error(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) -> ErrorGuaranteed {
1397 let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
1399 let mut label = false;
1400 if let Some((def_id, visitor)) = get_owner_return_paths(tcx, def_id) {
1401 let typeck_results = tcx.typeck(def_id);
1405 .filter_map(|expr| typeck_results.node_type_opt(expr.hir_id))
1406 .all(|ty| matches!(ty.kind(), ty::Never))
1411 .filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some())
1412 .map(|expr| expr.span)
1413 .collect::<Vec<Span>>();
1414 let span_len = spans.len();
1416 err.span_label(spans[0], "this returned value is of `!` type");
1418 let mut multispan: MultiSpan = spans.clone().into();
1420 multispan.push_span_label(span, "this returned value is of `!` type");
1422 err.span_note(multispan, "these returned values have a concrete \"never\" type");
1424 err.help("this error will resolve once the item's body returns a concrete type");
1426 let mut seen = FxHashSet::default();
1428 err.span_label(span, "recursive opaque type");
1430 for (sp, ty) in visitor
1433 .filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t)))
1434 .filter(|(_, ty)| !matches!(ty.kind(), ty::Never))
1436 struct OpaqueTypeCollector(Vec<DefId>);
1437 impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypeCollector {
1438 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1440 ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
1442 ControlFlow::CONTINUE
1444 _ => t.super_visit_with(self),
1448 let mut visitor = OpaqueTypeCollector(vec![]);
1449 ty.visit_with(&mut visitor);
1450 for def_id in visitor.0 {
1451 let ty_span = tcx.def_span(def_id);
1452 if !seen.contains(&ty_span) {
1453 err.span_label(ty_span, &format!("returning this opaque type `{ty}`"));
1454 seen.insert(ty_span);
1456 err.span_label(sp, &format!("returning here with type `{ty}`"));
1462 err.span_label(span, "cannot resolve opaque type");