1 //! "Collection" is the process of determining the type and other external
2 //! details of each item in Rust. Collection is specifically concerned
3 //! with *inter-procedural* things -- for example, for a function
4 //! definition, collection will figure out the type and signature of the
5 //! function, but it will not visit the *body* of the function in any way,
6 //! nor examine type annotations on local variables (that's the job of
9 //! Collecting is ultimately defined by a bundle of queries that
10 //! inquire after various facts about the items in the crate (e.g.,
11 //! `type_of`, `generics_of`, `predicates_of`, etc). See the `provide` function
14 //! At present, however, we do run collection across all items in the
15 //! crate as a kind of pass. This should eventually be factored away.
17 use crate::astconv::AstConv;
18 use crate::check::intrinsic::intrinsic_operation_unsafety;
21 use rustc_ast::{MetaItemKind, NestedMetaItem};
22 use rustc_attr::{list_contains_name, InlineAttr, InstructionSetAttr, OptimizeAttr};
23 use rustc_data_structures::captures::Captures;
24 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
25 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, StashKey};
27 use rustc_hir::def::CtorKind;
28 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
29 use rustc_hir::intravisit::{self, Visitor};
30 use rustc_hir::weak_lang_items;
31 use rustc_hir::{GenericParamKind, Node};
32 use rustc_middle::hir::nested_filter;
33 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
34 use rustc_middle::mir::mono::Linkage;
35 use rustc_middle::ty::query::Providers;
36 use rustc_middle::ty::util::{Discr, IntTypeExt};
37 use rustc_middle::ty::ReprOptions;
38 use rustc_middle::ty::{self, AdtKind, Const, DefIdTree, IsSuggestable, Ty, TyCtxt};
39 use rustc_session::lint;
40 use rustc_session::parse::feature_err;
41 use rustc_span::symbol::{kw, sym, Ident, Symbol};
43 use rustc_target::spec::{abi, SanitizerSet};
44 use rustc_trait_selection::traits::error_reporting::suggestions::NextTypeParamName;
52 ///////////////////////////////////////////////////////////////////////////
55 fn collect_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
56 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CollectItemTypesVisitor { tcx });
59 pub fn provide(providers: &mut Providers) {
60 *providers = Providers {
61 opt_const_param_of: type_of::opt_const_param_of,
62 type_of: type_of::type_of,
63 item_bounds: item_bounds::item_bounds,
64 explicit_item_bounds: item_bounds::explicit_item_bounds,
65 generics_of: generics_of::generics_of,
66 predicates_of: predicates_of::predicates_of,
67 predicates_defined_on,
68 explicit_predicates_of: predicates_of::explicit_predicates_of,
69 super_predicates_of: predicates_of::super_predicates_of,
70 super_predicates_that_define_assoc_type:
71 predicates_of::super_predicates_that_define_assoc_type,
72 trait_explicit_predicates_and_bounds: predicates_of::trait_explicit_predicates_and_bounds,
73 type_param_predicates: predicates_of::type_param_predicates,
83 collect_mod_item_types,
84 should_inherit_track_caller,
89 ///////////////////////////////////////////////////////////////////////////
91 /// Context specific to some particular item. This is what implements
94 /// # `ItemCtxt` vs `FnCtxt`
96 /// `ItemCtxt` is primarily used to type-check item signatures and lower them
97 /// from HIR to their [`ty::Ty`] representation, which is exposed using [`AstConv`].
98 /// It's also used for the bodies of items like structs where the body (the fields)
99 /// are just signatures.
101 /// This is in contrast to [`FnCtxt`], which is used to type-check bodies of
102 /// functions, closures, and `const`s -- anywhere that expressions and statements show up.
104 /// An important thing to note is that `ItemCtxt` does no inference -- it has no [`InferCtxt`] --
105 /// while `FnCtxt` does do inference.
107 /// [`FnCtxt`]: crate::check::FnCtxt
108 /// [`InferCtxt`]: rustc_infer::infer::InferCtxt
110 /// # Trait predicates
112 /// `ItemCtxt` has information about the predicates that are defined
113 /// on the trait. Unfortunately, this predicate information is
114 /// available in various different forms at various points in the
115 /// process. So we can't just store a pointer to e.g., the AST or the
116 /// parsed ty form, we have to be more flexible. To this end, the
117 /// `ItemCtxt` is parameterized by a `DefId` that it uses to satisfy
118 /// `get_type_parameter_bounds` requests, drawing the information from
119 /// the AST (`hir::Generics`), recursively.
120 pub struct ItemCtxt<'tcx> {
125 ///////////////////////////////////////////////////////////////////////////
128 pub(crate) struct HirPlaceholderCollector(pub(crate) Vec<Span>);
130 impl<'v> Visitor<'v> for HirPlaceholderCollector {
131 fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
132 if let hir::TyKind::Infer = t.kind {
135 intravisit::walk_ty(self, t)
137 fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
139 hir::GenericArg::Infer(inf) => {
140 self.0.push(inf.span);
141 intravisit::walk_inf(self, inf);
143 hir::GenericArg::Type(t) => self.visit_ty(t),
147 fn visit_array_length(&mut self, length: &'v hir::ArrayLen) {
148 if let &hir::ArrayLen::Infer(_, span) = length {
151 intravisit::walk_array_len(self, length)
155 struct CollectItemTypesVisitor<'tcx> {
159 /// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
160 /// and suggest adding type parameters in the appropriate place, taking into consideration any and
161 /// all already existing generic type parameters to avoid suggesting a name that is already in use.
162 pub(crate) fn placeholder_type_error<'tcx>(
164 generics: Option<&hir::Generics<'_>>,
165 placeholder_types: Vec<Span>,
167 hir_ty: Option<&hir::Ty<'_>>,
170 if placeholder_types.is_empty() {
174 placeholder_type_error_diag(tcx, generics, placeholder_types, vec![], suggest, hir_ty, kind)
178 pub(crate) fn placeholder_type_error_diag<'tcx>(
180 generics: Option<&hir::Generics<'_>>,
181 placeholder_types: Vec<Span>,
182 additional_spans: Vec<Span>,
184 hir_ty: Option<&hir::Ty<'_>>,
186 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
187 if placeholder_types.is_empty() {
188 return bad_placeholder(tcx, additional_spans, kind);
191 let params = generics.map(|g| g.params).unwrap_or_default();
192 let type_name = params.next_type_param_name(None);
193 let mut sugg: Vec<_> =
194 placeholder_types.iter().map(|sp| (*sp, (*type_name).to_string())).collect();
196 if let Some(generics) = generics {
197 if let Some(arg) = params.iter().find(|arg| {
198 matches!(arg.name, hir::ParamName::Plain(Ident { name: kw::Underscore, .. }))
200 // Account for `_` already present in cases like `struct S<_>(_);` and suggest
201 // `struct S<T>(T);` instead of `struct S<_, T>(T);`.
202 sugg.push((arg.span, (*type_name).to_string()));
203 } else if let Some(span) = generics.span_for_param_suggestion() {
204 // Account for bounds, we want `fn foo<T: E, K>(_: K)` not `fn foo<T, K: E>(_: K)`.
205 sugg.push((span, format!(", {}", type_name)));
207 sugg.push((generics.span, format!("<{}>", type_name)));
212 bad_placeholder(tcx, placeholder_types.into_iter().chain(additional_spans).collect(), kind);
214 // Suggest, but only if it is not a function in const or static
216 let mut is_fn = false;
217 let mut is_const_or_static = false;
219 if let Some(hir_ty) = hir_ty && let hir::TyKind::BareFn(_) = hir_ty.kind {
222 // Check if parent is const or static
223 let parent_id = tcx.hir().get_parent_node(hir_ty.hir_id);
224 let parent_node = tcx.hir().get(parent_id);
226 is_const_or_static = matches!(
228 Node::Item(&hir::Item {
229 kind: hir::ItemKind::Const(..) | hir::ItemKind::Static(..),
231 }) | Node::TraitItem(&hir::TraitItem {
232 kind: hir::TraitItemKind::Const(..),
234 }) | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Const(..), .. })
238 // if function is wrapped around a const or static,
239 // then don't show the suggestion
240 if !(is_fn && is_const_or_static) {
241 err.multipart_suggestion(
242 "use type parameters instead",
244 Applicability::HasPlaceholders,
252 fn reject_placeholder_type_signatures_in_item<'tcx>(
254 item: &'tcx hir::Item<'tcx>,
256 let (generics, suggest) = match &item.kind {
257 hir::ItemKind::Union(_, generics)
258 | hir::ItemKind::Enum(_, generics)
259 | hir::ItemKind::TraitAlias(generics, _)
260 | hir::ItemKind::Trait(_, _, generics, ..)
261 | hir::ItemKind::Impl(hir::Impl { generics, .. })
262 | hir::ItemKind::Struct(_, generics) => (generics, true),
263 hir::ItemKind::OpaqueTy(hir::OpaqueTy { generics, .. })
264 | hir::ItemKind::TyAlias(_, generics) => (generics, false),
265 // `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
269 let mut visitor = HirPlaceholderCollector::default();
270 visitor.visit_item(item);
272 placeholder_type_error(tcx, Some(generics), visitor.0, suggest, None, item.kind.descr());
275 impl<'tcx> Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
276 type NestedFilter = nested_filter::OnlyBodies;
278 fn nested_visit_map(&mut self) -> Self::Map {
282 fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
283 convert_item(self.tcx, item.item_id());
284 reject_placeholder_type_signatures_in_item(self.tcx, item);
285 intravisit::walk_item(self, item);
288 fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
289 for param in generics.params {
291 hir::GenericParamKind::Lifetime { .. } => {}
292 hir::GenericParamKind::Type { default: Some(_), .. } => {
293 let def_id = self.tcx.hir().local_def_id(param.hir_id);
294 self.tcx.ensure().type_of(def_id);
296 hir::GenericParamKind::Type { .. } => {}
297 hir::GenericParamKind::Const { default, .. } => {
298 let def_id = self.tcx.hir().local_def_id(param.hir_id);
299 self.tcx.ensure().type_of(def_id);
300 if let Some(default) = default {
301 let default_def_id = self.tcx.hir().local_def_id(default.hir_id);
302 // need to store default and type of default
303 self.tcx.ensure().type_of(default_def_id);
304 self.tcx.ensure().const_param_default(def_id);
309 intravisit::walk_generics(self, generics);
312 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
313 if let hir::ExprKind::Closure { .. } = expr.kind {
314 let def_id = self.tcx.hir().local_def_id(expr.hir_id);
315 self.tcx.ensure().generics_of(def_id);
316 // We do not call `type_of` for closures here as that
317 // depends on typecheck and would therefore hide
318 // any further errors in case one typeck fails.
320 intravisit::walk_expr(self, expr);
323 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
324 convert_trait_item(self.tcx, trait_item.trait_item_id());
325 intravisit::walk_trait_item(self, trait_item);
328 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
329 convert_impl_item(self.tcx, impl_item.impl_item_id());
330 intravisit::walk_impl_item(self, impl_item);
334 ///////////////////////////////////////////////////////////////////////////
335 // Utility types and common code for the above passes.
337 fn bad_placeholder<'tcx>(
339 mut spans: Vec<Span>,
341 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
342 let kind = if kind.ends_with('s') { format!("{}es", kind) } else { format!("{}s", kind) };
345 let mut err = struct_span_err!(
349 "the placeholder `_` is not allowed within types on item signatures for {}",
353 err.span_label(span, "not allowed in type signatures");
358 impl<'tcx> ItemCtxt<'tcx> {
359 pub fn new(tcx: TyCtxt<'tcx>, item_def_id: DefId) -> ItemCtxt<'tcx> {
360 ItemCtxt { tcx, item_def_id }
363 pub fn to_ty(&self, ast_ty: &hir::Ty<'_>) -> Ty<'tcx> {
364 <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_ty)
367 pub fn hir_id(&self) -> hir::HirId {
368 self.tcx.hir().local_def_id_to_hir_id(self.item_def_id.expect_local())
371 pub fn node(&self) -> hir::Node<'tcx> {
372 self.tcx.hir().get(self.hir_id())
376 impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
377 fn tcx(&self) -> TyCtxt<'tcx> {
381 fn item_def_id(&self) -> Option<DefId> {
382 Some(self.item_def_id)
385 fn get_type_parameter_bounds(
390 ) -> ty::GenericPredicates<'tcx> {
391 self.tcx.at(span).type_param_predicates((
393 def_id.expect_local(),
398 fn re_infer(&self, _: Option<&ty::GenericParamDef>, _: Span) -> Option<ty::Region<'tcx>> {
402 fn allow_ty_infer(&self) -> bool {
406 fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
407 self.tcx().ty_error_with_message(span, "bad placeholder type")
410 fn ct_infer(&self, ty: Ty<'tcx>, _: Option<&ty::GenericParamDef>, span: Span) -> Const<'tcx> {
411 let ty = self.tcx.fold_regions(ty, |r, _| match *r {
412 ty::ReErased => self.tcx.lifetimes.re_static,
415 self.tcx().const_error_with_message(ty, span, "bad placeholder constant")
418 fn projected_ty_from_poly_trait_ref(
422 item_segment: &hir::PathSegment<'_>,
423 poly_trait_ref: ty::PolyTraitRef<'tcx>,
425 if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
426 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
433 self.tcx().mk_projection(item_def_id, item_substs)
435 // There are no late-bound regions; we can just ignore the binder.
436 let mut err = struct_span_err!(
440 "cannot use the associated type of a trait \
441 with uninferred generic parameters"
445 hir::Node::Field(_) | hir::Node::Ctor(_) | hir::Node::Variant(_) => {
449 .expect_item(self.tcx.hir().get_parent_item(self.hir_id()).def_id);
451 hir::ItemKind::Enum(_, generics)
452 | hir::ItemKind::Struct(_, generics)
453 | hir::ItemKind::Union(_, generics) => {
454 let lt_name = get_new_lifetime_name(self.tcx, poly_trait_ref, generics);
455 let (lt_sp, sugg) = match generics.params {
456 [] => (generics.span, format!("<{}>", lt_name)),
458 (bound.span.shrink_to_lo(), format!("{}, ", lt_name))
461 let suggestions = vec![
464 span.with_hi(item_segment.ident.span.lo()),
467 // Replace the existing lifetimes with a new named lifetime.
468 self.tcx.replace_late_bound_regions_uncached(
471 self.tcx.mk_region(ty::ReEarlyBound(
472 ty::EarlyBoundRegion {
475 name: Symbol::intern(<_name),
483 err.multipart_suggestion(
484 "use a fully qualified path with explicit lifetimes",
486 Applicability::MaybeIncorrect,
492 hir::Node::Item(hir::Item {
494 hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..),
498 | hir::Node::ForeignItem(_)
499 | hir::Node::TraitItem(_)
500 | hir::Node::ImplItem(_) => {
501 err.span_suggestion_verbose(
502 span.with_hi(item_segment.ident.span.lo()),
503 "use a fully qualified path with inferred lifetimes",
506 // Erase named lt, we want `<A as B<'_>::C`, not `<A as B<'a>::C`.
507 self.tcx.anonymize_late_bound_regions(poly_trait_ref).skip_binder(),
509 Applicability::MaybeIncorrect,
515 self.tcx().ty_error()
519 fn normalize_ty(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
520 // Types in item signatures are not normalized to avoid undue dependencies.
524 fn set_tainted_by_errors(&self) {
525 // There's no obvious place to track this, so just let it go.
528 fn record_ty(&self, _hir_id: hir::HirId, _ty: Ty<'tcx>, _span: Span) {
529 // There's no place to record types from signatures?
533 /// Synthesize a new lifetime name that doesn't clash with any of the lifetimes already present.
534 fn get_new_lifetime_name<'tcx>(
536 poly_trait_ref: ty::PolyTraitRef<'tcx>,
537 generics: &hir::Generics<'tcx>,
539 let existing_lifetimes = tcx
540 .collect_referenced_late_bound_regions(&poly_trait_ref)
543 if let ty::BoundRegionKind::BrNamed(_, name) = lt {
544 Some(name.as_str().to_string())
549 .chain(generics.params.iter().filter_map(|param| {
550 if let hir::GenericParamKind::Lifetime { .. } = ¶m.kind {
551 Some(param.name.ident().as_str().to_string())
556 .collect::<FxHashSet<String>>();
558 let a_to_z_repeat_n = |n| {
559 (b'a'..=b'z').map(move |c| {
560 let mut s = '\''.to_string();
561 s.extend(std::iter::repeat(char::from(c)).take(n));
566 // If all single char lifetime names are present, we wrap around and double the chars.
567 (1..).flat_map(a_to_z_repeat_n).find(|lt| !existing_lifetimes.contains(lt.as_str())).unwrap()
570 fn convert_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
571 let it = tcx.hir().item(item_id);
572 debug!("convert: item {} with id {}", it.ident, it.hir_id());
573 let def_id = item_id.def_id.def_id;
576 // These don't define types.
577 hir::ItemKind::ExternCrate(_)
578 | hir::ItemKind::Use(..)
579 | hir::ItemKind::Macro(..)
580 | hir::ItemKind::Mod(_)
581 | hir::ItemKind::GlobalAsm(_) => {}
582 hir::ItemKind::ForeignMod { items, .. } => {
584 let item = tcx.hir().foreign_item(item.id);
585 tcx.ensure().generics_of(item.def_id);
586 tcx.ensure().type_of(item.def_id);
587 tcx.ensure().predicates_of(item.def_id);
589 hir::ForeignItemKind::Fn(..) => tcx.ensure().fn_sig(item.def_id),
590 hir::ForeignItemKind::Static(..) => {
591 let mut visitor = HirPlaceholderCollector::default();
592 visitor.visit_foreign_item(item);
593 placeholder_type_error(
606 hir::ItemKind::Enum(ref enum_definition, _) => {
607 tcx.ensure().generics_of(def_id);
608 tcx.ensure().type_of(def_id);
609 tcx.ensure().predicates_of(def_id);
610 convert_enum_variant_types(tcx, def_id.to_def_id(), enum_definition.variants);
612 hir::ItemKind::Impl { .. } => {
613 tcx.ensure().generics_of(def_id);
614 tcx.ensure().type_of(def_id);
615 tcx.ensure().impl_trait_ref(def_id);
616 tcx.ensure().predicates_of(def_id);
618 hir::ItemKind::Trait(..) => {
619 tcx.ensure().generics_of(def_id);
620 tcx.ensure().trait_def(def_id);
621 tcx.at(it.span).super_predicates_of(def_id);
622 tcx.ensure().predicates_of(def_id);
624 hir::ItemKind::TraitAlias(..) => {
625 tcx.ensure().generics_of(def_id);
626 tcx.at(it.span).super_predicates_of(def_id);
627 tcx.ensure().predicates_of(def_id);
629 hir::ItemKind::Struct(ref struct_def, _) | hir::ItemKind::Union(ref struct_def, _) => {
630 tcx.ensure().generics_of(def_id);
631 tcx.ensure().type_of(def_id);
632 tcx.ensure().predicates_of(def_id);
634 for f in struct_def.fields() {
635 let def_id = tcx.hir().local_def_id(f.hir_id);
636 tcx.ensure().generics_of(def_id);
637 tcx.ensure().type_of(def_id);
638 tcx.ensure().predicates_of(def_id);
641 if let Some(ctor_hir_id) = struct_def.ctor_hir_id() {
642 convert_variant_ctor(tcx, ctor_hir_id);
646 // Desugared from `impl Trait`, so visited by the function's return type.
647 hir::ItemKind::OpaqueTy(hir::OpaqueTy {
648 origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
652 // Don't call `type_of` on opaque types, since that depends on type
653 // checking function bodies. `check_item_type` ensures that it's called
655 hir::ItemKind::OpaqueTy(..) => {
656 tcx.ensure().generics_of(def_id);
657 tcx.ensure().predicates_of(def_id);
658 tcx.ensure().explicit_item_bounds(def_id);
660 hir::ItemKind::TyAlias(..)
661 | hir::ItemKind::Static(..)
662 | hir::ItemKind::Const(..)
663 | hir::ItemKind::Fn(..) => {
664 tcx.ensure().generics_of(def_id);
665 tcx.ensure().type_of(def_id);
666 tcx.ensure().predicates_of(def_id);
668 hir::ItemKind::Fn(..) => tcx.ensure().fn_sig(def_id),
669 hir::ItemKind::OpaqueTy(..) => tcx.ensure().item_bounds(def_id),
670 hir::ItemKind::Const(ty, ..) | hir::ItemKind::Static(ty, ..) => {
671 if !is_suggestable_infer_ty(ty) {
672 let mut visitor = HirPlaceholderCollector::default();
673 visitor.visit_item(it);
674 placeholder_type_error(tcx, None, visitor.0, false, None, it.kind.descr());
683 fn convert_trait_item(tcx: TyCtxt<'_>, trait_item_id: hir::TraitItemId) {
684 let trait_item = tcx.hir().trait_item(trait_item_id);
685 let def_id = trait_item_id.def_id;
686 tcx.ensure().generics_of(def_id);
688 match trait_item.kind {
689 hir::TraitItemKind::Fn(..) => {
690 tcx.ensure().type_of(def_id);
691 tcx.ensure().fn_sig(def_id);
694 hir::TraitItemKind::Const(.., Some(_)) => {
695 tcx.ensure().type_of(def_id);
698 hir::TraitItemKind::Const(hir_ty, _) => {
699 tcx.ensure().type_of(def_id);
700 // Account for `const C: _;`.
701 let mut visitor = HirPlaceholderCollector::default();
702 visitor.visit_trait_item(trait_item);
703 if !tcx.sess.diagnostic().has_stashed_diagnostic(hir_ty.span, StashKey::ItemNoType) {
704 placeholder_type_error(tcx, None, visitor.0, false, None, "constant");
708 hir::TraitItemKind::Type(_, Some(_)) => {
709 tcx.ensure().item_bounds(def_id);
710 tcx.ensure().type_of(def_id);
711 // Account for `type T = _;`.
712 let mut visitor = HirPlaceholderCollector::default();
713 visitor.visit_trait_item(trait_item);
714 placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
717 hir::TraitItemKind::Type(_, None) => {
718 tcx.ensure().item_bounds(def_id);
719 // #74612: Visit and try to find bad placeholders
720 // even if there is no concrete type.
721 let mut visitor = HirPlaceholderCollector::default();
722 visitor.visit_trait_item(trait_item);
724 placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
728 tcx.ensure().predicates_of(def_id);
731 fn convert_impl_item(tcx: TyCtxt<'_>, impl_item_id: hir::ImplItemId) {
732 let def_id = impl_item_id.def_id;
733 tcx.ensure().generics_of(def_id);
734 tcx.ensure().type_of(def_id);
735 tcx.ensure().predicates_of(def_id);
736 let impl_item = tcx.hir().impl_item(impl_item_id);
737 match impl_item.kind {
738 hir::ImplItemKind::Fn(..) => {
739 tcx.ensure().fn_sig(def_id);
741 hir::ImplItemKind::TyAlias(_) => {
742 // Account for `type T = _;`
743 let mut visitor = HirPlaceholderCollector::default();
744 visitor.visit_impl_item(impl_item);
746 placeholder_type_error(tcx, None, visitor.0, false, None, "associated type");
748 hir::ImplItemKind::Const(..) => {}
752 fn convert_variant_ctor(tcx: TyCtxt<'_>, ctor_id: hir::HirId) {
753 let def_id = tcx.hir().local_def_id(ctor_id);
754 tcx.ensure().generics_of(def_id);
755 tcx.ensure().type_of(def_id);
756 tcx.ensure().predicates_of(def_id);
759 fn convert_enum_variant_types(tcx: TyCtxt<'_>, def_id: DefId, variants: &[hir::Variant<'_>]) {
760 let def = tcx.adt_def(def_id);
761 let repr_type = def.repr().discr_type();
762 let initial = repr_type.initial_discriminant(tcx);
763 let mut prev_discr = None::<Discr<'_>>;
765 // fill the discriminant values and field types
766 for variant in variants {
767 let wrapped_discr = prev_discr.map_or(initial, |d| d.wrap_incr(tcx));
769 if let Some(ref e) = variant.disr_expr {
770 let expr_did = tcx.hir().local_def_id(e.hir_id);
771 def.eval_explicit_discr(tcx, expr_did.to_def_id())
772 } else if let Some(discr) = repr_type.disr_incr(tcx, prev_discr) {
775 struct_span_err!(tcx.sess, variant.span, E0370, "enum discriminant overflowed")
778 format!("overflowed on value after {}", prev_discr.unwrap()),
781 "explicitly set `{} = {}` if that is desired outcome",
782 variant.ident, wrapped_discr
787 .unwrap_or(wrapped_discr),
790 for f in variant.data.fields() {
791 let def_id = tcx.hir().local_def_id(f.hir_id);
792 tcx.ensure().generics_of(def_id);
793 tcx.ensure().type_of(def_id);
794 tcx.ensure().predicates_of(def_id);
797 // Convert the ctor, if any. This also registers the variant as
799 if let Some(ctor_hir_id) = variant.data.ctor_hir_id() {
800 convert_variant_ctor(tcx, ctor_hir_id);
807 variant_did: Option<LocalDefId>,
808 ctor_did: Option<LocalDefId>,
810 discr: ty::VariantDiscr,
811 def: &hir::VariantData<'_>,
812 adt_kind: ty::AdtKind,
813 parent_did: LocalDefId,
814 ) -> ty::VariantDef {
815 let mut seen_fields: FxHashMap<Ident, Span> = Default::default();
820 let fid = tcx.hir().local_def_id(f.hir_id);
821 let dup_span = seen_fields.get(&f.ident.normalize_to_macros_2_0()).cloned();
822 if let Some(prev_span) = dup_span {
823 tcx.sess.emit_err(errors::FieldAlreadyDeclared {
829 seen_fields.insert(f.ident.normalize_to_macros_2_0(), f.span);
832 ty::FieldDef { did: fid.to_def_id(), name: f.ident.name, vis: tcx.visibility(fid) }
835 let recovered = match def {
836 hir::VariantData::Struct(_, r) => *r,
841 variant_did.map(LocalDefId::to_def_id),
842 ctor_did.map(LocalDefId::to_def_id),
845 CtorKind::from_hir(def),
847 parent_did.to_def_id(),
849 adt_kind == AdtKind::Struct && tcx.has_attr(parent_did.to_def_id(), sym::non_exhaustive)
850 || variant_did.map_or(false, |variant_did| {
851 tcx.has_attr(variant_did.to_def_id(), sym::non_exhaustive)
856 fn adt_def<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AdtDef<'tcx> {
859 let def_id = def_id.expect_local();
860 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
861 let Node::Item(item) = tcx.hir().get(hir_id) else {
865 let repr = ReprOptions::new(tcx, def_id.to_def_id());
866 let (kind, variants) = match item.kind {
867 ItemKind::Enum(ref def, _) => {
868 let mut distance_from_explicit = 0;
873 let variant_did = Some(tcx.hir().local_def_id(v.id));
875 v.data.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
877 let discr = if let Some(ref e) = v.disr_expr {
878 distance_from_explicit = 0;
879 ty::VariantDiscr::Explicit(tcx.hir().local_def_id(e.hir_id).to_def_id())
881 ty::VariantDiscr::Relative(distance_from_explicit)
883 distance_from_explicit += 1;
898 (AdtKind::Enum, variants)
900 ItemKind::Struct(ref def, _) => {
901 let variant_did = None::<LocalDefId>;
902 let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
904 let variants = std::iter::once(convert_variant(
909 ty::VariantDiscr::Relative(0),
916 (AdtKind::Struct, variants)
918 ItemKind::Union(ref def, _) => {
919 let variant_did = None;
920 let ctor_did = def.ctor_hir_id().map(|hir_id| tcx.hir().local_def_id(hir_id));
922 let variants = std::iter::once(convert_variant(
927 ty::VariantDiscr::Relative(0),
934 (AdtKind::Union, variants)
938 tcx.alloc_adt_def(def_id.to_def_id(), kind, variants, repr)
941 fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef {
942 let item = tcx.hir().expect_item(def_id.expect_local());
944 let (is_auto, unsafety, items) = match item.kind {
945 hir::ItemKind::Trait(is_auto, unsafety, .., items) => {
946 (is_auto == hir::IsAuto::Yes, unsafety, items)
948 hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]),
949 _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"),
952 let paren_sugar = tcx.has_attr(def_id, sym::rustc_paren_sugar);
953 if paren_sugar && !tcx.features().unboxed_closures {
957 "the `#[rustc_paren_sugar]` attribute is a temporary means of controlling \
958 which traits can use parenthetical notation",
960 .help("add `#![feature(unboxed_closures)]` to the crate attributes to use it")
964 let is_marker = tcx.has_attr(def_id, sym::marker);
965 let skip_array_during_method_dispatch =
966 tcx.has_attr(def_id, sym::rustc_skip_array_during_method_dispatch);
967 let spec_kind = if tcx.has_attr(def_id, sym::rustc_unsafe_specialization_marker) {
968 ty::trait_def::TraitSpecializationKind::Marker
969 } else if tcx.has_attr(def_id, sym::rustc_specialization_trait) {
970 ty::trait_def::TraitSpecializationKind::AlwaysApplicable
972 ty::trait_def::TraitSpecializationKind::None
974 let must_implement_one_of = tcx
975 .get_attr(def_id, sym::rustc_must_implement_one_of)
976 // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]`
977 // and that they are all identifiers
978 .and_then(|attr| match attr.meta_item_list() {
979 Some(items) if items.len() < 2 => {
983 "the `#[rustc_must_implement_one_of]` attribute must be \
984 used with at least 2 args",
992 .map(|item| item.ident().ok_or(item.span()))
993 .collect::<Result<Box<[_]>, _>>()
996 .struct_span_err(span, "must be a name of an associated function")
1000 .zip(Some(attr.span)),
1001 // Error is reported by `rustc_attr!`
1004 // Check that all arguments of `#[rustc_must_implement_one_of]` reference
1005 // functions in the trait with default implementations
1006 .and_then(|(list, attr_span)| {
1007 let errors = list.iter().filter_map(|ident| {
1008 let item = items.iter().find(|item| item.ident == *ident);
1011 Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => {
1012 if !tcx.impl_defaultness(item.id.def_id).has_value() {
1016 "This function doesn't have a default implementation",
1018 .span_note(attr_span, "required by this annotation")
1028 .struct_span_err(item.span, "Not a function")
1029 .span_note(attr_span, "required by this annotation")
1031 "All `#[rustc_must_implement_one_of]` arguments \
1032 must be associated function names",
1038 .struct_span_err(ident.span, "Function not found in this trait")
1046 (errors.count() == 0).then_some(list)
1048 // Check for duplicates
1050 let mut set: FxHashMap<Symbol, Span> = FxHashMap::default();
1051 let mut no_dups = true;
1053 for ident in &*list {
1054 if let Some(dup) = set.insert(ident.name, ident.span) {
1056 .struct_span_err(vec![dup, ident.span], "Functions names are duplicated")
1058 "All `#[rustc_must_implement_one_of]` arguments \
1067 no_dups.then_some(list)
1076 skip_array_during_method_dispatch,
1078 must_implement_one_of,
1082 fn are_suggestable_generic_args(generic_args: &[hir::GenericArg<'_>]) -> bool {
1083 generic_args.iter().any(|arg| match arg {
1084 hir::GenericArg::Type(ty) => is_suggestable_infer_ty(ty),
1085 hir::GenericArg::Infer(_) => true,
1090 /// Whether `ty` is a type with `_` placeholders that can be inferred. Used in diagnostics only to
1091 /// use inference to provide suggestions for the appropriate type if possible.
1092 fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
1097 Slice(ty) => is_suggestable_infer_ty(ty),
1098 Array(ty, length) => {
1099 is_suggestable_infer_ty(ty) || matches!(length, hir::ArrayLen::Infer(_, _))
1101 Tup(tys) => tys.iter().any(is_suggestable_infer_ty),
1102 Ptr(mut_ty) | Rptr(_, mut_ty) => is_suggestable_infer_ty(mut_ty.ty),
1103 OpaqueDef(_, generic_args, _) => are_suggestable_generic_args(generic_args),
1104 Path(hir::QPath::TypeRelative(ty, segment)) => {
1105 is_suggestable_infer_ty(ty) || are_suggestable_generic_args(segment.args().args)
1107 Path(hir::QPath::Resolved(ty_opt, hir::Path { segments, .. })) => {
1108 ty_opt.map_or(false, is_suggestable_infer_ty)
1109 || segments.iter().any(|segment| are_suggestable_generic_args(segment.args().args))
1115 pub fn get_infer_ret_ty<'hir>(output: &'hir hir::FnRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
1116 if let hir::FnRetTy::Return(ty) = output {
1117 if is_suggestable_infer_ty(ty) {
1124 #[instrument(level = "debug", skip(tcx))]
1125 fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
1126 use rustc_hir::Node::*;
1129 let def_id = def_id.expect_local();
1130 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1132 let icx = ItemCtxt::new(tcx, def_id.to_def_id());
1134 match tcx.hir().get(hir_id) {
1135 TraitItem(hir::TraitItem {
1136 kind: TraitItemKind::Fn(sig, TraitFn::Provided(_)),
1140 | Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), .. }) => {
1141 infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1144 ImplItem(hir::ImplItem { kind: ImplItemKind::Fn(sig, _), generics, .. }) => {
1145 // Do not try to inference the return type for a impl method coming from a trait
1146 if let Item(hir::Item { kind: ItemKind::Impl(i), .. }) =
1147 tcx.hir().get(tcx.hir().get_parent_node(hir_id))
1148 && i.of_trait.is_some()
1150 <dyn AstConv<'_>>::ty_of_fn(
1153 sig.header.unsafety,
1160 infer_return_ty_for_fn_sig(tcx, sig, generics, def_id, &icx)
1164 TraitItem(hir::TraitItem {
1165 kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
1168 }) => <dyn AstConv<'_>>::ty_of_fn(
1178 ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(fn_decl, _, _), .. }) => {
1179 let abi = tcx.hir().get_foreign_abi(hir_id);
1180 compute_sig_of_foreign_fn_decl(tcx, def_id.to_def_id(), fn_decl, abi)
1183 Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor_hir_id().is_some() => {
1184 let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id));
1186 data.fields().iter().map(|f| tcx.type_of(tcx.hir().local_def_id(f.hir_id)));
1187 ty::Binder::dummy(tcx.mk_fn_sig(
1191 hir::Unsafety::Normal,
1196 Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
1197 // Closure signatures are not like other function
1198 // signatures and cannot be accessed through `fn_sig`. For
1199 // example, a closure signature excludes the `self`
1200 // argument. In any case they are embedded within the
1201 // closure type as part of the `ClosureSubsts`.
1203 // To get the signature of a closure, you should use the
1204 // `sig` method on the `ClosureSubsts`:
1206 // substs.as_closure().sig(def_id, tcx)
1208 "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
1213 bug!("unexpected sort of node in fn_sig(): {:?}", x);
1218 fn infer_return_ty_for_fn_sig<'tcx>(
1220 sig: &hir::FnSig<'_>,
1221 generics: &hir::Generics<'_>,
1223 icx: &ItemCtxt<'tcx>,
1224 ) -> ty::PolyFnSig<'tcx> {
1225 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
1227 match get_infer_ret_ty(&sig.decl.output) {
1229 let fn_sig = tcx.typeck(def_id).liberated_fn_sigs()[hir_id];
1230 // Typeck doesn't expect erased regions to be returned from `type_of`.
1231 let fn_sig = tcx.fold_regions(fn_sig, |r, _| match *r {
1232 ty::ReErased => tcx.lifetimes.re_static,
1235 let fn_sig = ty::Binder::dummy(fn_sig);
1237 let mut visitor = HirPlaceholderCollector::default();
1238 visitor.visit_ty(ty);
1239 let mut diag = bad_placeholder(tcx, visitor.0, "return type");
1240 let ret_ty = fn_sig.skip_binder().output();
1241 if ret_ty.is_suggestable(tcx, false) {
1242 diag.span_suggestion(
1244 "replace with the correct return type",
1246 Applicability::MachineApplicable,
1248 } else if matches!(ret_ty.kind(), ty::FnDef(..)) {
1249 let fn_sig = ret_ty.fn_sig(tcx);
1254 .all(|t| t.is_suggestable(tcx, false))
1256 diag.span_suggestion(
1258 "replace with the correct return type",
1260 Applicability::MachineApplicable,
1263 } else if ret_ty.is_closure() {
1264 // We're dealing with a closure, so we should suggest using `impl Fn` or trait bounds
1265 // to prevent the user from getting a papercut while trying to use the unique closure
1266 // syntax (e.g. `[closure@src/lib.rs:2:5: 2:9]`).
1267 diag.help("consider using an `Fn`, `FnMut`, or `FnOnce` trait bound");
1268 diag.note("for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html");
1274 None => <dyn AstConv<'_>>::ty_of_fn(
1277 sig.header.unsafety,
1286 fn impl_trait_ref(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ty::TraitRef<'_>> {
1287 let icx = ItemCtxt::new(tcx, def_id);
1288 match tcx.hir().expect_item(def_id.expect_local()).kind {
1289 hir::ItemKind::Impl(ref impl_) => impl_.of_trait.as_ref().map(|ast_trait_ref| {
1290 let selfty = tcx.type_of(def_id);
1291 <dyn AstConv<'_>>::instantiate_mono_trait_ref(&icx, ast_trait_ref, selfty)
1297 fn impl_polarity(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ImplPolarity {
1298 let is_rustc_reservation = tcx.has_attr(def_id, sym::rustc_reservation_impl);
1299 let item = tcx.hir().expect_item(def_id.expect_local());
1301 hir::ItemKind::Impl(hir::Impl {
1302 polarity: hir::ImplPolarity::Negative(span),
1306 if is_rustc_reservation {
1307 let span = span.to(of_trait.as_ref().map_or(*span, |t| t.path.span));
1308 tcx.sess.span_err(span, "reservation impls can't be negative");
1310 ty::ImplPolarity::Negative
1312 hir::ItemKind::Impl(hir::Impl {
1313 polarity: hir::ImplPolarity::Positive,
1317 if is_rustc_reservation {
1318 tcx.sess.span_err(item.span, "reservation impls can't be inherent");
1320 ty::ImplPolarity::Positive
1322 hir::ItemKind::Impl(hir::Impl {
1323 polarity: hir::ImplPolarity::Positive,
1327 if is_rustc_reservation {
1328 ty::ImplPolarity::Reservation
1330 ty::ImplPolarity::Positive
1333 item => bug!("impl_polarity: {:?} not an impl", item),
1337 /// Returns the early-bound lifetimes declared in this generics
1338 /// listing. For anything other than fns/methods, this is just all
1339 /// the lifetimes that are declared. For fns or methods, we have to
1340 /// screen out those that do not appear in any where-clauses etc using
1341 /// `resolve_lifetime::early_bound_lifetimes`.
1342 fn early_bound_lifetimes_from_generics<'a, 'tcx: 'a>(
1344 generics: &'a hir::Generics<'a>,
1345 ) -> impl Iterator<Item = &'a hir::GenericParam<'a>> + Captures<'tcx> {
1346 generics.params.iter().filter(move |param| match param.kind {
1347 GenericParamKind::Lifetime { .. } => !tcx.is_late_bound(param.hir_id),
1352 /// Returns a list of type predicates for the definition with ID `def_id`, including inferred
1353 /// lifetime constraints. This includes all predicates returned by `explicit_predicates_of`, plus
1354 /// inferred constraints concerning which regions outlive other regions.
1355 #[instrument(level = "debug", skip(tcx))]
1356 fn predicates_defined_on(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> {
1357 let mut result = tcx.explicit_predicates_of(def_id);
1358 debug!("predicates_defined_on: explicit_predicates_of({:?}) = {:?}", def_id, result,);
1359 let inferred_outlives = tcx.inferred_outlives_of(def_id);
1360 if !inferred_outlives.is_empty() {
1362 "predicates_defined_on: inferred_outlives_of({:?}) = {:?}",
1363 def_id, inferred_outlives,
1365 if result.predicates.is_empty() {
1366 result.predicates = inferred_outlives;
1368 result.predicates = tcx
1370 .alloc_from_iter(result.predicates.iter().chain(inferred_outlives).copied());
1374 debug!("predicates_defined_on({:?}) = {:?}", def_id, result);
1378 fn compute_sig_of_foreign_fn_decl<'tcx>(
1381 decl: &'tcx hir::FnDecl<'tcx>,
1383 ) -> ty::PolyFnSig<'tcx> {
1384 let unsafety = if abi == abi::Abi::RustIntrinsic {
1385 intrinsic_operation_unsafety(tcx, def_id)
1387 hir::Unsafety::Unsafe
1389 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
1390 let fty = <dyn AstConv<'_>>::ty_of_fn(
1391 &ItemCtxt::new(tcx, def_id),
1400 // Feature gate SIMD types in FFI, since I am not sure that the
1401 // ABIs are handled at all correctly. -huonw
1402 if abi != abi::Abi::RustIntrinsic
1403 && abi != abi::Abi::PlatformIntrinsic
1404 && !tcx.features().simd_ffi
1406 let check = |ast_ty: &hir::Ty<'_>, ty: Ty<'_>| {
1411 .span_to_snippet(ast_ty.span)
1412 .map_or_else(|_| String::new(), |s| format!(" `{}`", s));
1417 "use of SIMD type{} in FFI is highly experimental and \
1418 may result in invalid code",
1422 .help("add `#![feature(simd_ffi)]` to the crate attributes to enable")
1426 for (input, ty) in iter::zip(decl.inputs, fty.inputs().skip_binder()) {
1429 if let hir::FnRetTy::Return(ref ty) = decl.output {
1430 check(ty, fty.output().skip_binder())
1437 fn is_foreign_item(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
1438 match tcx.hir().get_if_local(def_id) {
1439 Some(Node::ForeignItem(..)) => true,
1441 _ => bug!("is_foreign_item applied to non-local def-id {:?}", def_id),
1445 fn generator_kind(tcx: TyCtxt<'_>, def_id: DefId) -> Option<hir::GeneratorKind> {
1446 match tcx.hir().get_if_local(def_id) {
1447 Some(Node::Expr(&rustc_hir::Expr {
1448 kind: rustc_hir::ExprKind::Closure(&rustc_hir::Closure { body, .. }),
1450 })) => tcx.hir().body(body).generator_kind(),
1452 _ => bug!("generator_kind applied to non-local def-id {:?}", def_id),
1456 fn from_target_feature(
1458 attr: &ast::Attribute,
1459 supported_target_features: &FxHashMap<String, Option<Symbol>>,
1460 target_features: &mut Vec<Symbol>,
1462 let Some(list) = attr.meta_item_list() else { return };
1463 let bad_item = |span| {
1464 let msg = "malformed `target_feature` attribute input";
1465 let code = "enable = \"..\"";
1467 .struct_span_err(span, msg)
1468 .span_suggestion(span, "must be of the form", code, Applicability::HasPlaceholders)
1471 let rust_features = tcx.features();
1473 // Only `enable = ...` is accepted in the meta-item list.
1474 if !item.has_name(sym::enable) {
1475 bad_item(item.span());
1479 // Must be of the form `enable = "..."` (a string).
1480 let Some(value) = item.value_str() else {
1481 bad_item(item.span());
1485 // We allow comma separation to enable multiple features.
1486 target_features.extend(value.as_str().split(',').filter_map(|feature| {
1487 let Some(feature_gate) = supported_target_features.get(feature) else {
1489 format!("the feature named `{}` is not valid for this target", feature);
1490 let mut err = tcx.sess.struct_span_err(item.span(), &msg);
1493 format!("`{}` is not valid for this target", feature),
1495 if let Some(stripped) = feature.strip_prefix('+') {
1496 let valid = supported_target_features.contains_key(stripped);
1498 err.help("consider removing the leading `+` in the feature name");
1505 // Only allow features whose feature gates have been enabled.
1506 let allowed = match feature_gate.as_ref().copied() {
1507 Some(sym::arm_target_feature) => rust_features.arm_target_feature,
1508 Some(sym::hexagon_target_feature) => rust_features.hexagon_target_feature,
1509 Some(sym::powerpc_target_feature) => rust_features.powerpc_target_feature,
1510 Some(sym::mips_target_feature) => rust_features.mips_target_feature,
1511 Some(sym::riscv_target_feature) => rust_features.riscv_target_feature,
1512 Some(sym::avx512_target_feature) => rust_features.avx512_target_feature,
1513 Some(sym::sse4a_target_feature) => rust_features.sse4a_target_feature,
1514 Some(sym::tbm_target_feature) => rust_features.tbm_target_feature,
1515 Some(sym::wasm_target_feature) => rust_features.wasm_target_feature,
1516 Some(sym::cmpxchg16b_target_feature) => rust_features.cmpxchg16b_target_feature,
1517 Some(sym::movbe_target_feature) => rust_features.movbe_target_feature,
1518 Some(sym::rtm_target_feature) => rust_features.rtm_target_feature,
1519 Some(sym::f16c_target_feature) => rust_features.f16c_target_feature,
1520 Some(sym::ermsb_target_feature) => rust_features.ermsb_target_feature,
1521 Some(sym::bpf_target_feature) => rust_features.bpf_target_feature,
1522 Some(sym::aarch64_ver_target_feature) => rust_features.aarch64_ver_target_feature,
1523 Some(name) => bug!("unknown target feature gate {}", name),
1528 &tcx.sess.parse_sess,
1529 feature_gate.unwrap(),
1531 &format!("the target feature `{}` is currently unstable", feature),
1535 Some(Symbol::intern(feature))
1540 fn linkage_by_name(tcx: TyCtxt<'_>, def_id: LocalDefId, name: &str) -> Linkage {
1541 use rustc_middle::mir::mono::Linkage::*;
1543 // Use the names from src/llvm/docs/LangRef.rst here. Most types are only
1544 // applicable to variable declarations and may not really make sense for
1545 // Rust code in the first place but allow them anyway and trust that the
1546 // user knows what they're doing. Who knows, unanticipated use cases may pop
1547 // up in the future.
1549 // ghost, dllimport, dllexport and linkonce_odr_autohide are not supported
1550 // and don't have to be, LLVM treats them as no-ops.
1552 "appending" => Appending,
1553 "available_externally" => AvailableExternally,
1555 "extern_weak" => ExternalWeak,
1556 "external" => External,
1557 "internal" => Internal,
1558 "linkonce" => LinkOnceAny,
1559 "linkonce_odr" => LinkOnceODR,
1560 "private" => Private,
1562 "weak_odr" => WeakODR,
1563 _ => tcx.sess.span_fatal(tcx.def_span(def_id), "invalid linkage specified"),
1567 fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: DefId) -> CodegenFnAttrs {
1568 if cfg!(debug_assertions) {
1569 let def_kind = tcx.def_kind(did);
1571 def_kind.has_codegen_attrs(),
1572 "unexpected `def_kind` in `codegen_fn_attrs`: {def_kind:?}",
1576 let did = did.expect_local();
1577 let attrs = tcx.hir().attrs(tcx.hir().local_def_id_to_hir_id(did));
1578 let mut codegen_fn_attrs = CodegenFnAttrs::new();
1579 if tcx.should_inherit_track_caller(did) {
1580 codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
1583 // The panic_no_unwind function called by TerminatorKind::Abort will never
1584 // unwind. If the panic handler that it invokes unwind then it will simply
1585 // call the panic handler again.
1586 if Some(did.to_def_id()) == tcx.lang_items().panic_no_unwind() {
1587 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
1590 let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);
1592 let mut inline_span = None;
1593 let mut link_ordinal_span = None;
1594 let mut no_sanitize_span = None;
1595 for attr in attrs.iter() {
1596 if attr.has_name(sym::cold) {
1597 codegen_fn_attrs.flags |= CodegenFnAttrFlags::COLD;
1598 } else if attr.has_name(sym::rustc_allocator) {
1599 codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR;
1600 } else if attr.has_name(sym::ffi_returns_twice) {
1601 if tcx.is_foreign_item(did) {
1602 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_RETURNS_TWICE;
1604 // `#[ffi_returns_twice]` is only allowed `extern fn`s.
1609 "`#[ffi_returns_twice]` may only be used on foreign functions"
1613 } else if attr.has_name(sym::ffi_pure) {
1614 if tcx.is_foreign_item(did) {
1615 if attrs.iter().any(|a| a.has_name(sym::ffi_const)) {
1616 // `#[ffi_const]` functions cannot be `#[ffi_pure]`
1621 "`#[ffi_const]` function cannot be `#[ffi_pure]`"
1625 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_PURE;
1628 // `#[ffi_pure]` is only allowed on foreign functions
1633 "`#[ffi_pure]` may only be used on foreign functions"
1637 } else if attr.has_name(sym::ffi_const) {
1638 if tcx.is_foreign_item(did) {
1639 codegen_fn_attrs.flags |= CodegenFnAttrFlags::FFI_CONST;
1641 // `#[ffi_const]` is only allowed on foreign functions
1646 "`#[ffi_const]` may only be used on foreign functions"
1650 } else if attr.has_name(sym::rustc_allocator_nounwind) {
1651 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
1652 } else if attr.has_name(sym::rustc_reallocator) {
1653 codegen_fn_attrs.flags |= CodegenFnAttrFlags::REALLOCATOR;
1654 } else if attr.has_name(sym::rustc_deallocator) {
1655 codegen_fn_attrs.flags |= CodegenFnAttrFlags::DEALLOCATOR;
1656 } else if attr.has_name(sym::rustc_allocator_zeroed) {
1657 codegen_fn_attrs.flags |= CodegenFnAttrFlags::ALLOCATOR_ZEROED;
1658 } else if attr.has_name(sym::naked) {
1659 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NAKED;
1660 } else if attr.has_name(sym::no_mangle) {
1661 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
1662 } else if attr.has_name(sym::no_coverage) {
1663 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_COVERAGE;
1664 } else if attr.has_name(sym::rustc_std_internal_symbol) {
1665 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
1666 } else if attr.has_name(sym::used) {
1667 let inner = attr.meta_item_list();
1668 match inner.as_deref() {
1669 Some([item]) if item.has_name(sym::linker) => {
1670 if !tcx.features().used_with_arg {
1672 &tcx.sess.parse_sess,
1675 "`#[used(linker)]` is currently unstable",
1679 codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER;
1681 Some([item]) if item.has_name(sym::compiler) => {
1682 if !tcx.features().used_with_arg {
1684 &tcx.sess.parse_sess,
1687 "`#[used(compiler)]` is currently unstable",
1691 codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED;
1694 tcx.sess.emit_err(errors::ExpectedUsedSymbol { span: attr.span });
1697 // Unfortunately, unconditionally using `llvm.used` causes
1698 // issues in handling `.init_array` with the gold linker,
1699 // but using `llvm.compiler.used` caused a nontrival amount
1700 // of unintentional ecosystem breakage -- particularly on
1703 // As a result, we emit `llvm.compiler.used` only on ELF
1704 // targets. This is somewhat ad-hoc, but actually follows
1705 // our pre-LLVM 13 behavior (prior to the ecosystem
1706 // breakage), and seems to match `clang`'s behavior as well
1707 // (both before and after LLVM 13), possibly because they
1708 // have similar compatibility concerns to us. See
1709 // https://github.com/rust-lang/rust/issues/47384#issuecomment-1019080146
1710 // and following comments for some discussion of this, as
1711 // well as the comments in `rustc_codegen_llvm` where these
1712 // flags are handled.
1714 // Anyway, to be clear: this is still up in the air
1715 // somewhat, and is subject to change in the future (which
1716 // is a good thing, because this would ideally be a bit
1718 let is_like_elf = !(tcx.sess.target.is_like_osx
1719 || tcx.sess.target.is_like_windows
1720 || tcx.sess.target.is_like_wasm);
1721 codegen_fn_attrs.flags |= if is_like_elf {
1722 CodegenFnAttrFlags::USED
1724 CodegenFnAttrFlags::USED_LINKER
1728 } else if attr.has_name(sym::cmse_nonsecure_entry) {
1729 if !matches!(tcx.fn_sig(did).abi(), abi::Abi::C { .. }) {
1734 "`#[cmse_nonsecure_entry]` requires C ABI"
1738 if !tcx.sess.target.llvm_target.contains("thumbv8m") {
1739 struct_span_err!(tcx.sess, attr.span, E0775, "`#[cmse_nonsecure_entry]` is only valid for targets with the TrustZone-M extension")
1742 codegen_fn_attrs.flags |= CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY;
1743 } else if attr.has_name(sym::thread_local) {
1744 codegen_fn_attrs.flags |= CodegenFnAttrFlags::THREAD_LOCAL;
1745 } else if attr.has_name(sym::track_caller) {
1746 if !tcx.is_closure(did.to_def_id()) && tcx.fn_sig(did).abi() != abi::Abi::Rust {
1747 struct_span_err!(tcx.sess, attr.span, E0737, "`#[track_caller]` requires Rust ABI")
1750 if tcx.is_closure(did.to_def_id()) && !tcx.features().closure_track_caller {
1752 &tcx.sess.parse_sess,
1753 sym::closure_track_caller,
1755 "`#[track_caller]` on closures is currently unstable",
1759 codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
1760 } else if attr.has_name(sym::export_name) {
1761 if let Some(s) = attr.value_str() {
1762 if s.as_str().contains('\0') {
1763 // `#[export_name = ...]` will be converted to a null-terminated string,
1764 // so it may not contain any null characters.
1769 "`export_name` may not contain null characters"
1773 codegen_fn_attrs.export_name = Some(s);
1775 } else if attr.has_name(sym::target_feature) {
1776 if !tcx.is_closure(did.to_def_id())
1777 && tcx.fn_sig(did).unsafety() == hir::Unsafety::Normal
1779 if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
1780 // The `#[target_feature]` attribute is allowed on
1781 // WebAssembly targets on all functions, including safe
1782 // ones. Other targets require that `#[target_feature]` is
1783 // only applied to unsafe functions (pending the
1784 // `target_feature_11` feature) because on most targets
1785 // execution of instructions that are not supported is
1786 // considered undefined behavior. For WebAssembly which is a
1787 // 100% safe target at execution time it's not possible to
1788 // execute undefined instructions, and even if a future
1789 // feature was added in some form for this it would be a
1790 // deterministic trap. There is no undefined behavior when
1791 // executing WebAssembly so `#[target_feature]` is allowed
1792 // on safe functions (but again, only for WebAssembly)
1794 // Note that this is also allowed if `actually_rustdoc` so
1795 // if a target is documenting some wasm-specific code then
1796 // it's not spuriously denied.
1797 } else if !tcx.features().target_feature_11 {
1798 let mut err = feature_err(
1799 &tcx.sess.parse_sess,
1800 sym::target_feature_11,
1802 "`#[target_feature(..)]` can only be applied to `unsafe` functions",
1804 err.span_label(tcx.def_span(did), "not an `unsafe` function");
1807 check_target_feature_trait_unsafe(tcx, did, attr.span);
1810 from_target_feature(
1813 supported_target_features,
1814 &mut codegen_fn_attrs.target_features,
1816 } else if attr.has_name(sym::linkage) {
1817 if let Some(val) = attr.value_str() {
1818 codegen_fn_attrs.linkage = Some(linkage_by_name(tcx, did, val.as_str()));
1820 } else if attr.has_name(sym::link_section) {
1821 if let Some(val) = attr.value_str() {
1822 if val.as_str().bytes().any(|b| b == 0) {
1824 "illegal null byte in link_section \
1828 tcx.sess.span_err(attr.span, &msg);
1830 codegen_fn_attrs.link_section = Some(val);
1833 } else if attr.has_name(sym::link_name) {
1834 codegen_fn_attrs.link_name = attr.value_str();
1835 } else if attr.has_name(sym::link_ordinal) {
1836 link_ordinal_span = Some(attr.span);
1837 if let ordinal @ Some(_) = check_link_ordinal(tcx, attr) {
1838 codegen_fn_attrs.link_ordinal = ordinal;
1840 } else if attr.has_name(sym::no_sanitize) {
1841 no_sanitize_span = Some(attr.span);
1842 if let Some(list) = attr.meta_item_list() {
1843 for item in list.iter() {
1844 if item.has_name(sym::address) {
1845 codegen_fn_attrs.no_sanitize |= SanitizerSet::ADDRESS;
1846 } else if item.has_name(sym::cfi) {
1847 codegen_fn_attrs.no_sanitize |= SanitizerSet::CFI;
1848 } else if item.has_name(sym::memory) {
1849 codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMORY;
1850 } else if item.has_name(sym::memtag) {
1851 codegen_fn_attrs.no_sanitize |= SanitizerSet::MEMTAG;
1852 } else if item.has_name(sym::shadow_call_stack) {
1853 codegen_fn_attrs.no_sanitize |= SanitizerSet::SHADOWCALLSTACK;
1854 } else if item.has_name(sym::thread) {
1855 codegen_fn_attrs.no_sanitize |= SanitizerSet::THREAD;
1856 } else if item.has_name(sym::hwaddress) {
1857 codegen_fn_attrs.no_sanitize |= SanitizerSet::HWADDRESS;
1860 .struct_span_err(item.span(), "invalid argument for `no_sanitize`")
1861 .note("expected one of: `address`, `cfi`, `hwaddress`, `memory`, `memtag`, `shadow-call-stack`, or `thread`")
1866 } else if attr.has_name(sym::instruction_set) {
1867 codegen_fn_attrs.instruction_set = match attr.meta_kind() {
1868 Some(MetaItemKind::List(ref items)) => match items.as_slice() {
1869 [NestedMetaItem::MetaItem(set)] => {
1871 set.path.segments.iter().map(|x| x.ident.name).collect::<Vec<_>>();
1872 match segments.as_slice() {
1873 [sym::arm, sym::a32] | [sym::arm, sym::t32] => {
1874 if !tcx.sess.target.has_thumb_interworking {
1876 tcx.sess.diagnostic(),
1879 "target does not support `#[instruction_set]`"
1883 } else if segments[1] == sym::a32 {
1884 Some(InstructionSetAttr::ArmA32)
1885 } else if segments[1] == sym::t32 {
1886 Some(InstructionSetAttr::ArmT32)
1893 tcx.sess.diagnostic(),
1896 "invalid instruction set specified",
1905 tcx.sess.diagnostic(),
1908 "`#[instruction_set]` requires an argument"
1915 tcx.sess.diagnostic(),
1918 "cannot specify more than one instruction set"
1926 tcx.sess.diagnostic(),
1929 "must specify an instruction set"
1935 } else if attr.has_name(sym::repr) {
1936 codegen_fn_attrs.alignment = match attr.meta_item_list() {
1937 Some(items) => match items.as_slice() {
1938 [item] => match item.name_value_literal() {
1939 Some((sym::align, literal)) => {
1940 let alignment = rustc_attr::parse_alignment(&literal.kind);
1943 Ok(align) => Some(align),
1946 tcx.sess.diagnostic(),
1949 "invalid `repr(align)` attribute: {}",
1968 codegen_fn_attrs.inline = attrs.iter().fold(InlineAttr::None, |ia, attr| {
1969 if !attr.has_name(sym::inline) {
1972 match attr.meta_kind() {
1973 Some(MetaItemKind::Word) => InlineAttr::Hint,
1974 Some(MetaItemKind::List(ref items)) => {
1975 inline_span = Some(attr.span);
1976 if items.len() != 1 {
1978 tcx.sess.diagnostic(),
1981 "expected one argument"
1985 } else if list_contains_name(&items, sym::always) {
1987 } else if list_contains_name(&items, sym::never) {
1991 tcx.sess.diagnostic(),
1996 .help("valid inline arguments are `always` and `never`")
2002 Some(MetaItemKind::NameValue(_)) => ia,
2007 codegen_fn_attrs.optimize = attrs.iter().fold(OptimizeAttr::None, |ia, attr| {
2008 if !attr.has_name(sym::optimize) {
2011 let err = |sp, s| struct_span_err!(tcx.sess.diagnostic(), sp, E0722, "{}", s).emit();
2012 match attr.meta_kind() {
2013 Some(MetaItemKind::Word) => {
2014 err(attr.span, "expected one argument");
2017 Some(MetaItemKind::List(ref items)) => {
2018 inline_span = Some(attr.span);
2019 if items.len() != 1 {
2020 err(attr.span, "expected one argument");
2022 } else if list_contains_name(&items, sym::size) {
2024 } else if list_contains_name(&items, sym::speed) {
2027 err(items[0].span(), "invalid argument");
2031 Some(MetaItemKind::NameValue(_)) => ia,
2036 // #73631: closures inherit `#[target_feature]` annotations
2037 if tcx.features().target_feature_11 && tcx.is_closure(did.to_def_id()) {
2038 let owner_id = tcx.parent(did.to_def_id());
2039 if tcx.def_kind(owner_id).has_codegen_attrs() {
2042 .extend(tcx.codegen_fn_attrs(owner_id).target_features.iter().copied());
2046 // If a function uses #[target_feature] it can't be inlined into general
2047 // purpose functions as they wouldn't have the right target features
2048 // enabled. For that reason we also forbid #[inline(always)] as it can't be
2050 if !codegen_fn_attrs.target_features.is_empty() {
2051 if codegen_fn_attrs.inline == InlineAttr::Always {
2052 if let Some(span) = inline_span {
2055 "cannot use `#[inline(always)]` with \
2056 `#[target_feature]`",
2062 if !codegen_fn_attrs.no_sanitize.is_empty() {
2063 if codegen_fn_attrs.inline == InlineAttr::Always {
2064 if let (Some(no_sanitize_span), Some(inline_span)) = (no_sanitize_span, inline_span) {
2065 let hir_id = tcx.hir().local_def_id_to_hir_id(did);
2066 tcx.struct_span_lint_hir(
2067 lint::builtin::INLINE_NO_SANITIZE,
2071 lint.build("`no_sanitize` will have no effect after inlining")
2072 .span_note(inline_span, "inlining requested here")
2080 // Weak lang items have the same semantics as "std internal" symbols in the
2081 // sense that they're preserved through all our LTO passes and only
2082 // strippable by the linker.
2084 // Additionally weak lang items have predetermined symbol names.
2085 if tcx.is_weak_lang_item(did.to_def_id()) {
2086 codegen_fn_attrs.flags |= CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL;
2088 if let Some(name) = weak_lang_items::link_name(attrs) {
2089 codegen_fn_attrs.export_name = Some(name);
2090 codegen_fn_attrs.link_name = Some(name);
2092 check_link_name_xor_ordinal(tcx, &codegen_fn_attrs, link_ordinal_span);
2094 // Internal symbols to the standard library all have no_mangle semantics in
2095 // that they have defined symbol names present in the function name. This
2096 // also applies to weak symbols where they all have known symbol names.
2097 if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL) {
2098 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NO_MANGLE;
2101 // Any linkage to LLVM intrinsics for now forcibly marks them all as never
2102 // unwinds since LLVM sometimes can't handle codegen which `invoke`s
2103 // intrinsic functions.
2104 if let Some(name) = &codegen_fn_attrs.link_name {
2105 if name.as_str().starts_with("llvm.") {
2106 codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
2113 /// Computes the set of target features used in a function for the purposes of
2114 /// inline assembly.
2115 fn asm_target_features<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx FxHashSet<Symbol> {
2116 let mut target_features = tcx.sess.unstable_target_features.clone();
2117 if tcx.def_kind(did).has_codegen_attrs() {
2118 let attrs = tcx.codegen_fn_attrs(did);
2119 target_features.extend(&attrs.target_features);
2120 match attrs.instruction_set {
2122 Some(InstructionSetAttr::ArmA32) => {
2123 target_features.remove(&sym::thumb_mode);
2125 Some(InstructionSetAttr::ArmT32) => {
2126 target_features.insert(sym::thumb_mode);
2131 tcx.arena.alloc(target_features)
2134 /// Checks if the provided DefId is a method in a trait impl for a trait which has track_caller
2135 /// applied to the method prototype.
2136 fn should_inherit_track_caller(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
2137 if let Some(impl_item) = tcx.opt_associated_item(def_id)
2138 && let ty::AssocItemContainer::ImplContainer = impl_item.container
2139 && let Some(trait_item) = impl_item.trait_item_def_id
2142 .codegen_fn_attrs(trait_item)
2144 .intersects(CodegenFnAttrFlags::TRACK_CALLER);
2150 fn check_link_ordinal(tcx: TyCtxt<'_>, attr: &ast::Attribute) -> Option<u16> {
2151 use rustc_ast::{Lit, LitIntType, LitKind};
2152 if !tcx.features().raw_dylib && tcx.sess.target.arch == "x86" {
2154 &tcx.sess.parse_sess,
2157 "`#[link_ordinal]` is unstable on x86",
2161 let meta_item_list = attr.meta_item_list();
2162 let meta_item_list: Option<&[ast::NestedMetaItem]> = meta_item_list.as_ref().map(Vec::as_ref);
2163 let sole_meta_list = match meta_item_list {
2164 Some([item]) => item.literal(),
2167 .struct_span_err(attr.span, "incorrect number of arguments to `#[link_ordinal]`")
2168 .note("the attribute requires exactly one argument")
2174 if let Some(Lit { kind: LitKind::Int(ordinal, LitIntType::Unsuffixed), .. }) = sole_meta_list {
2175 // According to the table at https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-header,
2176 // the ordinal must fit into 16 bits. Similarly, the Ordinal field in COFFShortExport (defined
2177 // in llvm/include/llvm/Object/COFFImportFile.h), which we use to communicate import information
2178 // to LLVM for `#[link(kind = "raw-dylib"_])`, is also defined to be uint16_t.
2180 // FIXME: should we allow an ordinal of 0? The MSVC toolchain has inconsistent support for this:
2181 // both LINK.EXE and LIB.EXE signal errors and abort when given a .DEF file that specifies
2182 // a zero ordinal. However, llvm-dlltool is perfectly happy to generate an import library
2183 // for such a .DEF file, and MSVC's LINK.EXE is also perfectly happy to consume an import
2184 // library produced by LLVM with an ordinal of 0, and it generates an .EXE. (I don't know yet
2185 // if the resulting EXE runs, as I haven't yet built the necessary DLL -- see earlier comment
2186 // about LINK.EXE failing.)
2187 if *ordinal <= u16::MAX as u128 {
2188 Some(*ordinal as u16)
2190 let msg = format!("ordinal value in `link_ordinal` is too large: `{}`", &ordinal);
2192 .struct_span_err(attr.span, &msg)
2193 .note("the value may not exceed `u16::MAX`")
2199 .struct_span_err(attr.span, "illegal ordinal format in `link_ordinal`")
2200 .note("an unsuffixed integer value, e.g., `1`, is expected")
2206 fn check_link_name_xor_ordinal(
2208 codegen_fn_attrs: &CodegenFnAttrs,
2209 inline_span: Option<Span>,
2211 if codegen_fn_attrs.link_name.is_none() || codegen_fn_attrs.link_ordinal.is_none() {
2214 let msg = "cannot use `#[link_name]` with `#[link_ordinal]`";
2215 if let Some(span) = inline_span {
2216 tcx.sess.span_err(span, msg);
2222 /// Checks the function annotated with `#[target_feature]` is not a safe
2223 /// trait method implementation, reporting an error if it is.
2224 fn check_target_feature_trait_unsafe(tcx: TyCtxt<'_>, id: LocalDefId, attr_span: Span) {
2225 let hir_id = tcx.hir().local_def_id_to_hir_id(id);
2226 let node = tcx.hir().get(hir_id);
2227 if let Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) = node {
2228 let parent_id = tcx.hir().get_parent_item(hir_id);
2229 let parent_item = tcx.hir().expect_item(parent_id.def_id);
2230 if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = parent_item.kind {
2234 "`#[target_feature(..)]` cannot be applied to safe trait method",
2236 .span_label(attr_span, "cannot be applied to safe trait method")
2237 .span_label(tcx.def_span(id), "not an `unsafe` function")