1 //! A pass that annotates every item and method with its stability level,
2 //! propagating default levels lexically from parent to children ast nodes.
4 use attr::StabilityLevel;
5 use rustc_attr::{self as attr, ConstStability, Stability, Unstable};
6 use rustc_data_structures::fx::{FxHashSet, FxIndexMap};
7 use rustc_errors::{struct_span_err, Applicability};
9 use rustc_hir::def::{DefKind, Res};
10 use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
11 use rustc_hir::hir_id::CRATE_HIR_ID;
12 use rustc_hir::intravisit::{self, Visitor};
13 use rustc_hir::{FieldDef, Generics, HirId, Item, ItemKind, TraitRef, Ty, TyKind, Variant};
14 use rustc_middle::hir::nested_filter;
15 use rustc_middle::middle::privacy::AccessLevels;
16 use rustc_middle::middle::stability::{AllowUnstable, DeprecationEntry, Index};
17 use rustc_middle::ty::{query::Providers, TyCtxt};
18 use rustc_session::lint;
19 use rustc_session::lint::builtin::{INEFFECTIVE_UNSTABLE_TRAIT_IMPL, USELESS_DEPRECATED};
20 use rustc_session::Session;
21 use rustc_span::symbol::{sym, Symbol};
23 use rustc_target::spec::abi::Abi;
25 use std::cmp::Ordering;
27 use std::mem::replace;
28 use std::num::NonZeroU32;
32 /// Annotation is required if not inherited from unstable parents.
34 /// Annotation is useless, reject it.
36 /// Deprecation annotation is useless, reject it. (Stability attribute is still required.)
37 DeprecationProhibited,
38 /// Annotation itself is useless, but it can be propagated to children.
42 /// Whether to inherit deprecation flags for nested items. In most cases, we do want to inherit
43 /// deprecation, because nested items rarely have individual deprecation attributes, and so
44 /// should be treated as deprecated if their parent is. However, default generic parameters
45 /// have separate deprecation attributes from their parents, so we do not wish to inherit
46 /// deprecation in this case. For example, inheriting deprecation for `T` in `Foo<T>`
47 /// would cause a duplicate warning arising from both `Foo` and `T` being deprecated.
49 enum InheritDeprecation {
54 impl InheritDeprecation {
55 fn yes(&self) -> bool {
56 matches!(self, InheritDeprecation::Yes)
60 /// Whether to inherit const stability flags for nested items. In most cases, we do not want to
61 /// inherit const stability: just because an enclosing `fn` is const-stable does not mean
62 /// all `extern` imports declared in it should be const-stable! However, trait methods
63 /// inherit const stability attributes from their parent and do not have their own.
64 enum InheritConstStability {
69 impl InheritConstStability {
70 fn yes(&self) -> bool {
71 matches!(self, InheritConstStability::Yes)
75 enum InheritStability {
80 impl InheritStability {
81 fn yes(&self) -> bool {
82 matches!(self, InheritStability::Yes)
86 /// A private tree-walker for producing an `Index`.
87 struct Annotator<'a, 'tcx> {
90 parent_stab: Option<Stability>,
91 parent_const_stab: Option<ConstStability>,
92 parent_depr: Option<DeprecationEntry>,
96 impl<'a, 'tcx> Annotator<'a, 'tcx> {
97 /// Determine the stability for a node based on its attributes and inherited stability. The
98 /// stability is recorded in the index and used as the parent. If the node is a function,
99 /// `fn_sig` is its signature.
104 fn_sig: Option<&'tcx hir::FnSig<'tcx>>,
105 kind: AnnotationKind,
106 inherit_deprecation: InheritDeprecation,
107 inherit_const_stability: InheritConstStability,
108 inherit_from_parent: InheritStability,
111 F: FnOnce(&mut Self),
113 let attrs = self.tcx.hir().attrs(self.tcx.hir().local_def_id_to_hir_id(def_id));
114 debug!("annotate(id = {:?}, attrs = {:?})", def_id, attrs);
116 let depr = attr::find_deprecation(&self.tcx.sess, attrs);
117 let mut is_deprecated = false;
118 if let Some((depr, span)) = &depr {
119 is_deprecated = true;
121 if kind == AnnotationKind::Prohibited || kind == AnnotationKind::DeprecationProhibited {
122 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
123 self.tcx.struct_span_lint_hir(USELESS_DEPRECATED, hir_id, *span, |lint| {
124 lint.build("this `#[deprecated]` annotation has no effect")
125 .span_suggestion_short(
127 "remove the unnecessary deprecation attribute",
129 rustc_errors::Applicability::MachineApplicable,
135 // `Deprecation` is just two pointers, no need to intern it
136 let depr_entry = DeprecationEntry::local(*depr, def_id);
137 self.index.depr_map.insert(def_id, depr_entry);
138 } else if let Some(parent_depr) = self.parent_depr {
139 if inherit_deprecation.yes() {
140 is_deprecated = true;
141 info!("tagging child {:?} as deprecated from parent", def_id);
142 self.index.depr_map.insert(def_id, parent_depr);
146 if !self.tcx.features().staged_api {
147 // Propagate unstability. This can happen even for non-staged-api crates in case
148 // -Zforce-unstable-if-unmarked is set.
149 if let Some(stab) = self.parent_stab {
150 if inherit_deprecation.yes() && stab.is_unstable() {
151 self.index.stab_map.insert(def_id, stab);
155 self.recurse_with_stability_attrs(
156 depr.map(|(d, _)| DeprecationEntry::local(d, def_id)),
164 let (stab, const_stab) = attr::find_stability(&self.tcx.sess, attrs, item_sp);
165 let mut const_span = None;
167 let const_stab = const_stab.map(|(const_stab, const_span_node)| {
168 self.index.const_stab_map.insert(def_id, const_stab);
169 const_span = Some(const_span_node);
173 // If the current node is a function, has const stability attributes and if it doesn not have an intrinsic ABI,
174 // check if the function/method is const or the parent impl block is const
175 if let (Some(const_span), Some(fn_sig)) = (const_span, fn_sig) {
176 if fn_sig.header.abi != Abi::RustIntrinsic
177 && fn_sig.header.abi != Abi::PlatformIntrinsic
178 && !fn_sig.header.is_const()
180 if !self.in_trait_impl
181 || (self.in_trait_impl && !self.tcx.is_const_fn_raw(def_id.to_def_id()))
183 missing_const_err(&self.tcx.sess, fn_sig.span, const_span);
188 // `impl const Trait for Type` items forward their const stability to their
189 // immediate children.
190 if const_stab.is_none() {
191 debug!("annotate: const_stab not found, parent = {:?}", self.parent_const_stab);
192 if let Some(parent) = self.parent_const_stab {
193 if parent.is_const_unstable() {
194 self.index.const_stab_map.insert(def_id, parent);
199 if let Some((rustc_attr::Deprecation { is_since_rustc_version: true, .. }, span)) = &depr {
205 "deprecated attribute must be paired with \
206 either stable or unstable attribute"
212 let stab = stab.map(|(stab, span)| {
213 // Error if prohibited, or can't inherit anything from a container.
214 if kind == AnnotationKind::Prohibited
215 || (kind == AnnotationKind::Container && stab.level.is_stable() && is_deprecated)
217 self.tcx.sess.struct_span_err(span,"this stability annotation is useless")
218 .span_label(span, "useless stability annotation")
219 .span_label(item_sp, "the stability attribute annotates this item")
223 debug!("annotate: found {:?}", stab);
225 // Check if deprecated_since < stable_since. If it is,
226 // this is *almost surely* an accident.
227 if let (&Some(dep_since), &attr::Stable { since: stab_since, .. }) =
228 (&depr.as_ref().and_then(|(d, _)| d.since), &stab.level)
230 // Explicit version of iter::order::lt to handle parse errors properly
231 for (dep_v, stab_v) in
232 iter::zip(dep_since.as_str().split('.'), stab_since.as_str().split('.'))
234 match stab_v.parse::<u64>() {
236 self.tcx.sess.struct_span_err(span, "invalid stability version found")
237 .span_label(span, "invalid stability version")
238 .span_label(item_sp, "the stability attribute annotates this item")
242 Ok(stab_vp) => match dep_v.parse::<u64>() {
243 Ok(dep_vp) => match dep_vp.cmp(&stab_vp) {
245 self.tcx.sess.struct_span_err(span, "an API can't be stabilized after it is deprecated")
246 .span_label(span, "invalid version")
247 .span_label(item_sp, "the stability attribute annotates this item")
251 Ordering::Equal => continue,
252 Ordering::Greater => break,
256 self.tcx.sess.struct_span_err(span, "invalid deprecation version found")
257 .span_label(span, "invalid deprecation version")
258 .span_label(item_sp, "the stability attribute annotates this item")
268 if let Stability { level: Unstable { implied_by: Some(implied_by), .. }, feature } = stab {
269 self.index.implications.insert(implied_by, feature);
272 self.index.stab_map.insert(def_id, stab);
277 debug!("annotate: stab not found, parent = {:?}", self.parent_stab);
278 if let Some(stab) = self.parent_stab {
279 if inherit_deprecation.yes() && stab.is_unstable() || inherit_from_parent.yes() {
280 self.index.stab_map.insert(def_id, stab);
285 self.recurse_with_stability_attrs(
286 depr.map(|(d, _)| DeprecationEntry::local(d, def_id)),
288 if inherit_const_stability.yes() { const_stab } else { None },
293 fn recurse_with_stability_attrs(
295 depr: Option<DeprecationEntry>,
296 stab: Option<Stability>,
297 const_stab: Option<ConstStability>,
298 f: impl FnOnce(&mut Self),
300 // These will be `Some` if this item changes the corresponding stability attribute.
301 let mut replaced_parent_depr = None;
302 let mut replaced_parent_stab = None;
303 let mut replaced_parent_const_stab = None;
305 if let Some(depr) = depr {
306 replaced_parent_depr = Some(replace(&mut self.parent_depr, Some(depr)));
308 if let Some(stab) = stab {
309 replaced_parent_stab = Some(replace(&mut self.parent_stab, Some(stab)));
311 if let Some(const_stab) = const_stab {
312 replaced_parent_const_stab =
313 Some(replace(&mut self.parent_const_stab, Some(const_stab)));
318 if let Some(orig_parent_depr) = replaced_parent_depr {
319 self.parent_depr = orig_parent_depr;
321 if let Some(orig_parent_stab) = replaced_parent_stab {
322 self.parent_stab = orig_parent_stab;
324 if let Some(orig_parent_const_stab) = replaced_parent_const_stab {
325 self.parent_const_stab = orig_parent_const_stab;
330 impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
331 /// Because stability levels are scoped lexically, we want to walk
332 /// nested items in the context of the outer item, so enable
334 type NestedFilter = nested_filter::All;
336 fn nested_visit_map(&mut self) -> Self::Map {
340 fn visit_item(&mut self, i: &'tcx Item<'tcx>) {
341 let orig_in_trait_impl = self.in_trait_impl;
342 let mut kind = AnnotationKind::Required;
343 let mut const_stab_inherit = InheritConstStability::No;
344 let mut fn_sig = None;
347 // Inherent impls and foreign modules serve only as containers for other items,
348 // they don't have their own stability. They still can be annotated as unstable
349 // and propagate this instability to children, but this annotation is completely
350 // optional. They inherit stability from their parents when unannotated.
351 hir::ItemKind::Impl(hir::Impl { of_trait: None, .. })
352 | hir::ItemKind::ForeignMod { .. } => {
353 self.in_trait_impl = false;
354 kind = AnnotationKind::Container;
356 hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => {
357 self.in_trait_impl = true;
358 kind = AnnotationKind::DeprecationProhibited;
359 const_stab_inherit = InheritConstStability::Yes;
361 hir::ItemKind::Struct(ref sd, _) => {
362 if let Some(ctor_hir_id) = sd.ctor_hir_id() {
364 self.tcx.hir().local_def_id(ctor_hir_id),
367 AnnotationKind::Required,
368 InheritDeprecation::Yes,
369 InheritConstStability::No,
370 InheritStability::Yes,
375 hir::ItemKind::Fn(ref item_fn_sig, _, _) => {
376 fn_sig = Some(item_fn_sig);
386 InheritDeprecation::Yes,
388 InheritStability::No,
389 |v| intravisit::walk_item(v, i),
391 self.in_trait_impl = orig_in_trait_impl;
394 fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
395 let fn_sig = match ti.kind {
396 hir::TraitItemKind::Fn(ref fn_sig, _) => Some(fn_sig),
404 AnnotationKind::Required,
405 InheritDeprecation::Yes,
406 InheritConstStability::No,
407 InheritStability::No,
409 intravisit::walk_trait_item(v, ti);
414 fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
416 if self.in_trait_impl { AnnotationKind::Prohibited } else { AnnotationKind::Required };
418 let fn_sig = match ii.kind {
419 hir::ImplItemKind::Fn(ref fn_sig, _) => Some(fn_sig),
428 InheritDeprecation::Yes,
429 InheritConstStability::No,
430 InheritStability::No,
432 intravisit::walk_impl_item(v, ii);
437 fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) {
439 self.tcx.hir().local_def_id(var.id),
442 AnnotationKind::Required,
443 InheritDeprecation::Yes,
444 InheritConstStability::No,
445 InheritStability::Yes,
447 if let Some(ctor_hir_id) = var.data.ctor_hir_id() {
449 v.tcx.hir().local_def_id(ctor_hir_id),
452 AnnotationKind::Required,
453 InheritDeprecation::Yes,
454 InheritConstStability::No,
455 InheritStability::No,
460 intravisit::walk_variant(v, var, g, item_id)
465 fn visit_field_def(&mut self, s: &'tcx FieldDef<'tcx>) {
467 self.tcx.hir().local_def_id(s.hir_id),
470 AnnotationKind::Required,
471 InheritDeprecation::Yes,
472 InheritConstStability::No,
473 InheritStability::Yes,
475 intravisit::walk_field_def(v, s);
480 fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) {
485 AnnotationKind::Required,
486 InheritDeprecation::Yes,
487 InheritConstStability::No,
488 InheritStability::No,
490 intravisit::walk_foreign_item(v, i);
495 fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
496 let kind = match &p.kind {
497 // Allow stability attributes on default generic arguments.
498 hir::GenericParamKind::Type { default: Some(_), .. }
499 | hir::GenericParamKind::Const { default: Some(_), .. } => AnnotationKind::Container,
500 _ => AnnotationKind::Prohibited,
504 self.tcx.hir().local_def_id(p.hir_id),
508 InheritDeprecation::No,
509 InheritConstStability::No,
510 InheritStability::No,
512 intravisit::walk_generic_param(v, p);
518 struct MissingStabilityAnnotations<'tcx> {
520 access_levels: &'tcx AccessLevels,
523 impl<'tcx> MissingStabilityAnnotations<'tcx> {
524 fn check_missing_stability(&self, def_id: LocalDefId, span: Span) {
525 let stab = self.tcx.stability().local_stability(def_id);
526 if !self.tcx.sess.opts.test && stab.is_none() && self.access_levels.is_reachable(def_id) {
527 let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
528 self.tcx.sess.span_err(span, &format!("{} has missing stability attribute", descr));
532 fn check_missing_const_stability(&self, def_id: LocalDefId, span: Span) {
533 if !self.tcx.features().staged_api {
537 let is_const = self.tcx.is_const_fn(def_id.to_def_id())
538 || self.tcx.is_const_trait_impl_raw(def_id.to_def_id());
541 .lookup_stability(def_id)
542 .map_or(false, |stability| stability.level.is_stable());
543 let missing_const_stability_attribute = self.tcx.lookup_const_stability(def_id).is_none();
544 let is_reachable = self.access_levels.is_reachable(def_id);
546 if is_const && is_stable && missing_const_stability_attribute && is_reachable {
547 let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
548 self.tcx.sess.span_err(span, &format!("{descr} has missing const stability attribute"));
553 impl<'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'tcx> {
554 type NestedFilter = nested_filter::OnlyBodies;
556 fn nested_visit_map(&mut self) -> Self::Map {
560 fn visit_item(&mut self, i: &'tcx Item<'tcx>) {
561 // Inherent impls and foreign modules serve only as containers for other items,
562 // they don't have their own stability. They still can be annotated as unstable
563 // and propagate this instability to children, but this annotation is completely
564 // optional. They inherit stability from their parents when unannotated.
567 hir::ItemKind::Impl(hir::Impl { of_trait: None, .. })
568 | hir::ItemKind::ForeignMod { .. }
570 self.check_missing_stability(i.def_id, i.span);
573 // Ensure stable `const fn` have a const stability attribute.
574 self.check_missing_const_stability(i.def_id, i.span);
576 intravisit::walk_item(self, i)
579 fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
580 self.check_missing_stability(ti.def_id, ti.span);
581 intravisit::walk_trait_item(self, ti);
584 fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
585 let impl_def_id = self.tcx.hir().get_parent_item(ii.hir_id());
586 if self.tcx.impl_trait_ref(impl_def_id).is_none() {
587 self.check_missing_stability(ii.def_id, ii.span);
588 self.check_missing_const_stability(ii.def_id, ii.span);
590 intravisit::walk_impl_item(self, ii);
593 fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) {
594 self.check_missing_stability(self.tcx.hir().local_def_id(var.id), var.span);
595 intravisit::walk_variant(self, var, g, item_id);
598 fn visit_field_def(&mut self, s: &'tcx FieldDef<'tcx>) {
599 self.check_missing_stability(self.tcx.hir().local_def_id(s.hir_id), s.span);
600 intravisit::walk_field_def(self, s);
603 fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) {
604 self.check_missing_stability(i.def_id, i.span);
605 intravisit::walk_foreign_item(self, i);
607 // Note that we don't need to `check_missing_stability` for default generic parameters,
608 // as we assume that any default generic parameters without attributes are automatically
609 // stable (assuming they have not inherited instability from their parent).
612 fn stability_index(tcx: TyCtxt<'_>, (): ()) -> Index {
613 let mut index = Index {
614 stab_map: Default::default(),
615 const_stab_map: Default::default(),
616 depr_map: Default::default(),
617 implications: Default::default(),
621 let mut annotator = Annotator {
625 parent_const_stab: None,
627 in_trait_impl: false,
630 // If the `-Z force-unstable-if-unmarked` flag is passed then we provide
631 // a parent stability annotation which indicates that this is private
632 // with the `rustc_private` feature. This is intended for use when
633 // compiling `librustc_*` crates themselves so we can leverage crates.io
634 // while maintaining the invariant that all sysroot crates are unstable
635 // by default and are unable to be used.
636 if tcx.sess.opts.unstable_opts.force_unstable_if_unmarked {
637 let reason = "this crate is being loaded from the sysroot, an \
638 unstable location; did you mean to load this crate \
639 from crates.io via `Cargo.toml` instead?";
640 let stability = Stability {
641 level: attr::StabilityLevel::Unstable {
642 reason: Some(Symbol::intern(reason)),
643 issue: NonZeroU32::new(27812),
647 feature: sym::rustc_private,
649 annotator.parent_stab = Some(stability);
654 tcx.hir().span(CRATE_HIR_ID),
656 AnnotationKind::Required,
657 InheritDeprecation::Yes,
658 InheritConstStability::No,
659 InheritStability::No,
660 |v| tcx.hir().walk_toplevel_module(v),
666 /// Cross-references the feature names of unstable APIs with enabled
667 /// features and possibly prints errors.
668 fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
669 tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx });
672 pub(crate) fn provide(providers: &mut Providers) {
673 *providers = Providers {
674 check_mod_unstable_api_usage,
676 stability_implications: |tcx, _| tcx.stability().implications.clone(),
677 lookup_stability: |tcx, id| tcx.stability().local_stability(id.expect_local()),
678 lookup_const_stability: |tcx, id| tcx.stability().local_const_stability(id.expect_local()),
679 lookup_deprecation_entry: |tcx, id| {
680 tcx.stability().local_deprecation_entry(id.expect_local())
686 struct Checker<'tcx> {
690 impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
691 type NestedFilter = nested_filter::OnlyBodies;
693 /// Because stability levels are scoped lexically, we want to walk
694 /// nested items in the context of the outer item, so enable
696 fn nested_visit_map(&mut self) -> Self::Map {
700 fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
702 hir::ItemKind::ExternCrate(_) => {
703 // compiler-generated `extern crate` items have a dummy span.
704 // `std` is still checked for the `restricted-std` feature.
705 if item.span.is_dummy() && item.ident.name != sym::std {
709 let Some(cnum) = self.tcx.extern_mod_stmt_cnum(item.def_id) else {
712 let def_id = cnum.as_def_id();
713 self.tcx.check_stability(def_id, Some(item.hir_id()), item.span, None);
716 // For implementations of traits, check the stability of each item
717 // individually as it's possible to have a stable trait with unstable
719 hir::ItemKind::Impl(hir::Impl {
720 of_trait: Some(ref t),
726 let features = self.tcx.features();
727 if features.staged_api {
728 let attrs = self.tcx.hir().attrs(item.hir_id());
729 let (stab, const_stab) = attr::find_stability(&self.tcx.sess, attrs, item.span);
731 // If this impl block has an #[unstable] attribute, give an
732 // error if all involved types and traits are stable, because
733 // it will have no effect.
734 // See: https://github.com/rust-lang/rust/issues/55436
735 if let Some((Stability { level: attr::Unstable { .. }, .. }, span)) = stab {
736 let mut c = CheckTraitImplStable { tcx: self.tcx, fully_stable: true };
738 c.visit_trait_ref(t);
740 self.tcx.struct_span_lint_hir(
741 INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
745 .build("an `#[unstable]` annotation here has no effect")
746 .note("see issue #55436 <https://github.com/rust-lang/rust/issues/55436> for more information")
752 // `#![feature(const_trait_impl)]` is unstable, so any impl declared stable
753 // needs to have an error emitted.
754 if features.const_trait_impl
755 && *constness == hir::Constness::Const
756 && const_stab.map_or(false, |(stab, _)| stab.is_const_stable())
760 .struct_span_err(item.span, "trait implementations cannot be const stable yet")
761 .note("see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information")
766 for impl_item_ref in *items {
767 let impl_item = self.tcx.associated_item(impl_item_ref.id.def_id);
769 if let Some(def_id) = impl_item.trait_item_def_id {
770 // Pass `None` to skip deprecation warnings.
771 self.tcx.check_stability(def_id, None, impl_item_ref.span, None);
778 intravisit::walk_item(self, item);
781 fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) {
782 if let Some(def_id) = path.res.opt_def_id() {
783 let method_span = path.segments.last().map(|s| s.ident.span);
784 let item_is_allowed = self.tcx.check_stability_allow_unstable(
789 if is_unstable_reexport(self.tcx, id) {
796 let is_allowed_through_unstable_modules = |def_id| {
798 .lookup_stability(def_id)
799 .map(|stab| match stab.level {
800 StabilityLevel::Stable { allowed_through_unstable_modules, .. } => {
801 allowed_through_unstable_modules
808 if item_is_allowed && !is_allowed_through_unstable_modules(def_id) {
809 // Check parent modules stability as well if the item the path refers to is itself
810 // stable. We only emit warnings for unstable path segments if the item is stable
811 // or allowed because stability is often inherited, so the most common case is that
812 // both the segments and the item are unstable behind the same feature flag.
814 // We check here rather than in `visit_path_segment` to prevent visiting the last
815 // path segment twice
817 // We include special cases via #[rustc_allowed_through_unstable_modules] for items
818 // that were accidentally stabilized through unstable paths before this check was
819 // added, such as `core::intrinsics::transmute`
820 let parents = path.segments.iter().rev().skip(1);
821 for path_segment in parents {
822 if let Some(def_id) = path_segment.res.as_ref().and_then(Res::opt_def_id) {
823 // use `None` for id to prevent deprecation check
824 self.tcx.check_stability_allow_unstable(
829 if is_unstable_reexport(self.tcx, id) {
840 intravisit::walk_path(self, path)
844 /// Check whether a path is a `use` item that has been marked as unstable.
846 /// See issue #94972 for details on why this is a special case
847 fn is_unstable_reexport<'tcx>(tcx: TyCtxt<'tcx>, id: hir::HirId) -> bool {
848 // Get the LocalDefId so we can lookup the item to check the kind.
849 let Some(def_id) = tcx.hir().opt_local_def_id(id) else { return false; };
851 let Some(stab) = tcx.stability().local_stability(def_id) else {
855 if stab.level.is_stable() {
856 // The re-export is not marked as unstable, don't override
860 // If this is a path that isn't a use, we don't need to do anything special
861 if !matches!(tcx.hir().item(hir::ItemId { def_id }).kind, ItemKind::Use(..)) {
868 struct CheckTraitImplStable<'tcx> {
873 impl<'tcx> Visitor<'tcx> for CheckTraitImplStable<'tcx> {
874 fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _id: hir::HirId) {
875 if let Some(def_id) = path.res.opt_def_id() {
876 if let Some(stab) = self.tcx.lookup_stability(def_id) {
877 self.fully_stable &= stab.level.is_stable();
880 intravisit::walk_path(self, path)
883 fn visit_trait_ref(&mut self, t: &'tcx TraitRef<'tcx>) {
884 if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
885 if let Some(stab) = self.tcx.lookup_stability(trait_did) {
886 self.fully_stable &= stab.level.is_stable();
889 intravisit::walk_trait_ref(self, t)
892 fn visit_ty(&mut self, t: &'tcx Ty<'tcx>) {
893 if let TyKind::Never = t.kind {
894 self.fully_stable = false;
896 intravisit::walk_ty(self, t)
900 /// Given the list of enabled features that were not language features (i.e., that
901 /// were expected to be library features), and the list of features used from
902 /// libraries, identify activated features that don't exist and error about them.
903 pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
905 tcx.sess.opts.unstable_opts.force_unstable_if_unmarked || tcx.features().staged_api;
907 let access_levels = &tcx.privacy_access_levels(());
908 let mut missing = MissingStabilityAnnotations { tcx, access_levels };
909 missing.check_missing_stability(CRATE_DEF_ID, tcx.hir().span(CRATE_HIR_ID));
910 tcx.hir().walk_toplevel_module(&mut missing);
911 tcx.hir().visit_all_item_likes_in_crate(&mut missing);
914 let declared_lang_features = &tcx.features().declared_lang_features;
915 let mut lang_features = FxHashSet::default();
916 for &(feature, span, since) in declared_lang_features {
917 if let Some(since) = since {
918 // Warn if the user has enabled an already-stable lang feature.
919 unnecessary_stable_feature_lint(tcx, span, feature, since);
921 if !lang_features.insert(feature) {
922 // Warn if the user enables a lang feature multiple times.
923 duplicate_feature_err(tcx.sess, span, feature);
927 let declared_lib_features = &tcx.features().declared_lib_features;
928 let mut remaining_lib_features = FxIndexMap::default();
929 for (feature, span) in declared_lib_features {
930 if !tcx.sess.opts.unstable_features.is_nightly_build() {
935 "`#![feature]` may not be used on the {} release channel",
936 env!("CFG_RELEASE_CHANNEL")
940 if remaining_lib_features.contains_key(&feature) {
941 // Warn if the user enables a lib feature multiple times.
942 duplicate_feature_err(tcx.sess, *span, *feature);
944 remaining_lib_features.insert(feature, *span);
946 // `stdbuild` has special handling for `libc`, so we need to
947 // recognise the feature when building std.
948 // Likewise, libtest is handled specially, so `test` isn't
949 // available as we'd like it to be.
950 // FIXME: only remove `libc` when `stdbuild` is active.
951 // FIXME: remove special casing for `test`.
952 remaining_lib_features.remove(&sym::libc);
953 remaining_lib_features.remove(&sym::test);
955 let mut implications = tcx.stability_implications(rustc_hir::def_id::LOCAL_CRATE).clone();
956 for &cnum in tcx.crates(()) {
957 implications.extend(tcx.stability_implications(cnum));
960 let check_features = |remaining_lib_features: &mut FxIndexMap<_, _>, defined_features: &[_]| {
961 for &(feature, since) in defined_features {
962 if let Some(since) = since && let Some(span) = remaining_lib_features.get(&feature) {
963 // Warn if the user has enabled an already-stable lib feature.
964 if let Some(implies) = implications.get(&feature) {
965 unnecessary_partially_stable_feature_lint(tcx, *span, feature, *implies, since);
967 unnecessary_stable_feature_lint(tcx, *span, feature, since);
970 remaining_lib_features.remove(&feature);
971 if remaining_lib_features.is_empty() {
977 // We always collect the lib features declared in the current crate, even if there are
978 // no unknown features, because the collection also does feature attribute validation.
979 let local_defined_features = tcx.lib_features(()).to_vec();
980 if !remaining_lib_features.is_empty() {
981 check_features(&mut remaining_lib_features, &local_defined_features);
983 for &cnum in tcx.crates(()) {
984 if remaining_lib_features.is_empty() {
987 check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
991 for (feature, span) in remaining_lib_features {
992 struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
995 // FIXME(#44232): the `used_features` table no longer exists, so we
996 // don't lint about unused features. We should re-enable this one day!
999 fn unnecessary_partially_stable_feature_lint(
1006 tcx.struct_span_lint_hir(lint::builtin::STABLE_FEATURES, hir::CRATE_HIR_ID, span, |lint| {
1007 lint.build(&format!(
1008 "the feature `{feature}` has been partially stabilized since {since} and is succeeded \
1009 by the feature `{implies}`"
1014 "if you are using features which are still unstable, change to using `{implies}`"
1017 Applicability::MaybeIncorrect,
1020 tcx.sess.source_map().span_extend_to_line(span),
1021 "if you are using features which are now stable, remove this line",
1023 Applicability::MaybeIncorrect,
1029 fn unnecessary_stable_feature_lint(tcx: TyCtxt<'_>, span: Span, feature: Symbol, since: Symbol) {
1030 tcx.struct_span_lint_hir(lint::builtin::STABLE_FEATURES, hir::CRATE_HIR_ID, span, |lint| {
1031 lint.build(&format!(
1032 "the feature `{feature}` has been stable since {since} and no longer requires an \
1033 attribute to enable",
1039 fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
1040 struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)
1044 fn missing_const_err(session: &Session, fn_sig_span: Span, const_span: Span) {
1045 const ERROR_MSG: &'static str = "attributes `#[rustc_const_unstable]` \
1046 and `#[rustc_const_stable]` require \
1047 the function or method to be `const`";
1050 .struct_span_err(fn_sig_span, ERROR_MSG)
1051 .span_help(fn_sig_span, "make the function or method const")
1052 .span_label(const_span, "attribute specified here")