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 pub use self::StabilityLevel::*;
6 use crate::lint::{self, Lint, in_derive_expansion};
7 use crate::lint::builtin::BuiltinLintDiagnostics;
8 use crate::hir::{self, Item, Generics, StructField, Variant, HirId};
9 use crate::hir::def::{Res, DefKind};
10 use crate::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, LOCAL_CRATE};
11 use crate::hir::intravisit::{self, Visitor, NestedVisitorMap};
12 use crate::ty::query::Providers;
13 use crate::middle::privacy::AccessLevels;
14 use crate::session::{DiagnosticMessageId, Session};
15 use errors::DiagnosticBuilder;
16 use syntax::symbol::{Symbol, sym};
17 use syntax_pos::{Span, MultiSpan};
18 use syntax::ast::{Attribute, CRATE_NODE_ID};
19 use syntax::errors::Applicability;
20 use syntax::feature_gate::{GateIssue, emit_feature_err};
21 use syntax::attr::{self, Stability, Deprecation, RustcDeprecation};
22 use crate::ty::{self, TyCtxt};
23 use crate::util::nodemap::{FxHashSet, FxHashMap};
25 use std::cmp::Ordering;
26 use std::mem::replace;
27 use std::num::NonZeroU32;
29 #[derive(PartialEq, Clone, Copy, Debug)]
30 pub enum StabilityLevel {
36 pub fn from_attr_level(level: &attr::StabilityLevel) -> Self {
37 if level.is_stable() { Stable } else { Unstable }
43 // Annotation is required if not inherited from unstable parents
45 // Annotation is useless, reject it
47 // Annotation itself is useless, but it can be propagated to children
51 /// An entry in the `depr_map`.
53 pub struct DeprecationEntry {
54 /// The metadata of the attribute associated with this entry.
55 pub attr: Deprecation,
56 /// The `DefId` where the attr was originally attached. `None` for non-local
58 origin: Option<HirId>,
61 impl_stable_hash_for!(struct self::DeprecationEntry {
66 impl DeprecationEntry {
67 fn local(attr: Deprecation, id: HirId) -> DeprecationEntry {
74 pub fn external(attr: Deprecation) -> DeprecationEntry {
81 pub fn same_origin(&self, other: &DeprecationEntry) -> bool {
82 match (self.origin, other.origin) {
83 (Some(o1), Some(o2)) => o1 == o2,
89 /// A stability index, giving the stability level for items and methods.
90 pub struct Index<'tcx> {
91 /// This is mostly a cache, except the stabilities of local items
92 /// are filled by the annotator.
93 stab_map: FxHashMap<HirId, &'tcx Stability>,
94 depr_map: FxHashMap<HirId, DeprecationEntry>,
96 /// Maps for each crate whether it is part of the staged API.
97 staged_api: FxHashMap<CrateNum, bool>,
99 /// Features enabled for this crate.
100 active_features: FxHashSet<Symbol>,
103 impl_stable_hash_for!(struct self::Index<'tcx> {
110 // A private tree-walker for producing an Index.
111 struct Annotator<'a, 'tcx> {
113 index: &'a mut Index<'tcx>,
114 parent_stab: Option<&'tcx Stability>,
115 parent_depr: Option<DeprecationEntry>,
119 impl<'a, 'tcx> Annotator<'a, 'tcx> {
120 // Determine the stability for a node based on its attributes and inherited
121 // stability. The stability is recorded in the index and used as the parent.
122 fn annotate<F>(&mut self, hir_id: HirId, attrs: &[Attribute],
123 item_sp: Span, kind: AnnotationKind, visit_children: F)
124 where F: FnOnce(&mut Self)
126 if self.tcx.features().staged_api {
127 // This crate explicitly wants staged API.
128 debug!("annotate(id = {:?}, attrs = {:?})", hir_id, attrs);
129 if let Some(..) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
130 self.tcx.sess.span_err(item_sp, "`#[deprecated]` cannot be used in staged API; \
131 use `#[rustc_deprecated]` instead");
133 if let Some(mut stab) = attr::find_stability(&self.tcx.sess.parse_sess,
135 // Error if prohibited, or can't inherit anything from a container.
136 if kind == AnnotationKind::Prohibited ||
137 (kind == AnnotationKind::Container &&
138 stab.level.is_stable() &&
139 stab.rustc_depr.is_none()) {
140 self.tcx.sess.span_err(item_sp, "This stability annotation is useless");
143 debug!("annotate: found {:?}", stab);
144 // If parent is deprecated and we're not, inherit this by merging
145 // deprecated_since and its reason.
146 if let Some(parent_stab) = self.parent_stab {
147 if parent_stab.rustc_depr.is_some() && stab.rustc_depr.is_none() {
148 stab.rustc_depr = parent_stab.rustc_depr.clone()
152 let stab = self.tcx.intern_stability(stab);
154 // Check if deprecated_since < stable_since. If it is,
155 // this is *almost surely* an accident.
156 if let (&Some(attr::RustcDeprecation {since: dep_since, ..}),
157 &attr::Stable {since: stab_since}) = (&stab.rustc_depr, &stab.level) {
158 // Explicit version of iter::order::lt to handle parse errors properly
159 for (dep_v, stab_v) in dep_since.as_str()
161 .zip(stab_since.as_str().split('.'))
163 if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
164 match dep_v.cmp(&stab_v) {
166 self.tcx.sess.span_err(item_sp, "An API can't be stabilized \
167 after it is deprecated");
170 Ordering::Equal => continue,
171 Ordering::Greater => break,
174 // Act like it isn't less because the question is now nonsensical,
175 // and this makes us not do anything else interesting.
176 self.tcx.sess.span_err(item_sp, "Invalid stability or deprecation \
183 self.index.stab_map.insert(hir_id, stab);
185 let orig_parent_stab = replace(&mut self.parent_stab, Some(stab));
186 visit_children(self);
187 self.parent_stab = orig_parent_stab;
189 debug!("annotate: not found, parent = {:?}", self.parent_stab);
190 if let Some(stab) = self.parent_stab {
191 if stab.level.is_unstable() {
192 self.index.stab_map.insert(hir_id, stab);
195 visit_children(self);
198 // Emit errors for non-staged-api crates.
200 let name = attr.name_or_empty();
201 if [sym::unstable, sym::stable, sym::rustc_deprecated].contains(&name) {
202 attr::mark_used(attr);
207 "stability attributes may not be used outside of the standard library",
212 // Propagate unstability. This can happen even for non-staged-api crates in case
213 // -Zforce-unstable-if-unmarked is set.
214 if let Some(stab) = self.parent_stab {
215 if stab.level.is_unstable() {
216 self.index.stab_map.insert(hir_id, stab);
220 if let Some(depr) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
221 if kind == AnnotationKind::Prohibited {
222 self.tcx.sess.span_err(item_sp, "This deprecation annotation is useless");
225 // `Deprecation` is just two pointers, no need to intern it
226 let depr_entry = DeprecationEntry::local(depr, hir_id);
227 self.index.depr_map.insert(hir_id, depr_entry.clone());
229 let orig_parent_depr = replace(&mut self.parent_depr,
231 visit_children(self);
232 self.parent_depr = orig_parent_depr;
233 } else if let Some(parent_depr) = self.parent_depr.clone() {
234 self.index.depr_map.insert(hir_id, parent_depr);
235 visit_children(self);
237 visit_children(self);
243 impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
244 /// Because stability levels are scoped lexically, we want to walk
245 /// nested items in the context of the outer item, so enable
247 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
248 NestedVisitorMap::All(&self.tcx.hir())
251 fn visit_item(&mut self, i: &'tcx Item) {
252 let orig_in_trait_impl = self.in_trait_impl;
253 let mut kind = AnnotationKind::Required;
255 // Inherent impls and foreign modules serve only as containers for other items,
256 // they don't have their own stability. They still can be annotated as unstable
257 // and propagate this unstability to children, but this annotation is completely
258 // optional. They inherit stability from their parents when unannotated.
259 hir::ItemKind::Impl(.., None, _, _) | hir::ItemKind::ForeignMod(..) => {
260 self.in_trait_impl = false;
261 kind = AnnotationKind::Container;
263 hir::ItemKind::Impl(.., Some(_), _, _) => {
264 self.in_trait_impl = true;
266 hir::ItemKind::Struct(ref sd, _) => {
267 if let Some(ctor_hir_id) = sd.ctor_hir_id() {
268 self.annotate(ctor_hir_id, &i.attrs, i.span, AnnotationKind::Required, |_| {})
274 self.annotate(i.hir_id, &i.attrs, i.span, kind, |v| {
275 intravisit::walk_item(v, i)
277 self.in_trait_impl = orig_in_trait_impl;
280 fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem) {
281 self.annotate(ti.hir_id, &ti.attrs, ti.span, AnnotationKind::Required, |v| {
282 intravisit::walk_trait_item(v, ti);
286 fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
287 let kind = if self.in_trait_impl {
288 AnnotationKind::Prohibited
290 AnnotationKind::Required
292 self.annotate(ii.hir_id, &ii.attrs, ii.span, kind, |v| {
293 intravisit::walk_impl_item(v, ii);
297 fn visit_variant(&mut self, var: &'tcx Variant, g: &'tcx Generics, item_id: HirId) {
298 self.annotate(var.id, &var.attrs, var.span, AnnotationKind::Required,
300 if let Some(ctor_hir_id) = var.data.ctor_hir_id() {
301 v.annotate(ctor_hir_id, &var.attrs, var.span, AnnotationKind::Required,
305 intravisit::walk_variant(v, var, g, item_id)
309 fn visit_struct_field(&mut self, s: &'tcx StructField) {
310 self.annotate(s.hir_id, &s.attrs, s.span, AnnotationKind::Required, |v| {
311 intravisit::walk_struct_field(v, s);
315 fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem) {
316 self.annotate(i.hir_id, &i.attrs, i.span, AnnotationKind::Required, |v| {
317 intravisit::walk_foreign_item(v, i);
321 fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
322 self.annotate(md.hir_id, &md.attrs, md.span, AnnotationKind::Required, |_| {});
326 struct MissingStabilityAnnotations<'a, 'tcx> {
328 access_levels: &'a AccessLevels,
331 impl<'a, 'tcx> MissingStabilityAnnotations<'a, 'tcx> {
332 fn check_missing_stability(&self, hir_id: HirId, span: Span, name: &str) {
333 let stab = self.tcx.stability().local_stability(hir_id);
334 let is_error = !self.tcx.sess.opts.test &&
336 self.access_levels.is_reachable(hir_id);
338 self.tcx.sess.span_err(
340 &format!("{} has missing stability attribute", name),
346 impl<'a, 'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'a, 'tcx> {
347 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
348 NestedVisitorMap::OnlyBodies(&self.tcx.hir())
351 fn visit_item(&mut self, i: &'tcx Item) {
353 // Inherent impls and foreign modules serve only as containers for other items,
354 // they don't have their own stability. They still can be annotated as unstable
355 // and propagate this unstability to children, but this annotation is completely
356 // optional. They inherit stability from their parents when unannotated.
357 hir::ItemKind::Impl(.., None, _, _) | hir::ItemKind::ForeignMod(..) => {}
359 _ => self.check_missing_stability(i.hir_id, i.span, i.kind.descriptive_variant())
362 intravisit::walk_item(self, i)
365 fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem) {
366 self.check_missing_stability(ti.hir_id, ti.span, "item");
367 intravisit::walk_trait_item(self, ti);
370 fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
371 let impl_def_id = self.tcx.hir().local_def_id(
372 self.tcx.hir().get_parent_item(ii.hir_id));
373 if self.tcx.impl_trait_ref(impl_def_id).is_none() {
374 self.check_missing_stability(ii.hir_id, ii.span, "item");
376 intravisit::walk_impl_item(self, ii);
379 fn visit_variant(&mut self, var: &'tcx Variant, g: &'tcx Generics, item_id: HirId) {
380 self.check_missing_stability(var.id, var.span, "variant");
381 intravisit::walk_variant(self, var, g, item_id);
384 fn visit_struct_field(&mut self, s: &'tcx StructField) {
385 self.check_missing_stability(s.hir_id, s.span, "field");
386 intravisit::walk_struct_field(self, s);
389 fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem) {
390 self.check_missing_stability(i.hir_id, i.span, i.kind.descriptive_variant());
391 intravisit::walk_foreign_item(self, i);
394 fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
395 self.check_missing_stability(md.hir_id, md.span, "macro");
399 impl<'tcx> Index<'tcx> {
400 pub fn new(tcx: TyCtxt<'tcx>) -> Index<'tcx> {
402 tcx.sess.opts.debugging_opts.force_unstable_if_unmarked ||
403 tcx.features().staged_api;
404 let mut staged_api = FxHashMap::default();
405 staged_api.insert(LOCAL_CRATE, is_staged_api);
406 let mut index = Index {
408 stab_map: Default::default(),
409 depr_map: Default::default(),
410 active_features: Default::default(),
413 let active_lib_features = &tcx.features().declared_lib_features;
414 let active_lang_features = &tcx.features().declared_lang_features;
416 // Put the active features into a map for quick lookup.
417 index.active_features =
418 active_lib_features.iter().map(|&(ref s, ..)| s.clone())
419 .chain(active_lang_features.iter().map(|&(ref s, ..)| s.clone()))
423 let krate = tcx.hir().krate();
424 let mut annotator = Annotator {
429 in_trait_impl: false,
432 // If the `-Z force-unstable-if-unmarked` flag is passed then we provide
433 // a parent stability annotation which indicates that this is private
434 // with the `rustc_private` feature. This is intended for use when
435 // compiling librustc crates themselves so we can leverage crates.io
436 // while maintaining the invariant that all sysroot crates are unstable
437 // by default and are unable to be used.
438 if tcx.sess.opts.debugging_opts.force_unstable_if_unmarked {
439 let reason = "this crate is being loaded from the sysroot, an \
440 unstable location; did you mean to load this crate \
441 from crates.io via `Cargo.toml` instead?";
442 let stability = tcx.intern_stability(Stability {
443 level: attr::StabilityLevel::Unstable {
444 reason: Some(Symbol::intern(reason)),
445 issue: NonZeroU32::new(27812),
448 feature: sym::rustc_private,
450 const_stability: None,
452 allow_const_fn_ptr: false,
454 annotator.parent_stab = Some(stability);
457 annotator.annotate(hir::CRATE_HIR_ID,
460 AnnotationKind::Required,
461 |v| intravisit::walk_crate(v, krate));
466 pub fn local_stability(&self, id: HirId) -> Option<&'tcx Stability> {
467 self.stab_map.get(&id).cloned()
470 pub fn local_deprecation_entry(&self, id: HirId) -> Option<DeprecationEntry> {
471 self.depr_map.get(&id).cloned()
475 /// Cross-references the feature names of unstable APIs with enabled
476 /// features and possibly prints errors.
477 fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, module_def_id: DefId) {
478 tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx }.as_deep_visitor());
481 pub fn provide(providers: &mut Providers<'_>) {
482 *providers = Providers {
483 check_mod_unstable_api_usage,
488 pub fn report_unstable(
491 reason: Option<Symbol>,
492 issue: Option<NonZeroU32>,
495 soft_handler: impl FnOnce(&'static lint::Lint, Span, &str),
497 let msg = match reason {
498 Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
499 None => format!("use of unstable library feature '{}'", &feature)
502 let msp: MultiSpan = span.into();
503 let cm = &sess.parse_sess.source_map();
504 let span_key = msp.primary_span().and_then(|sp: Span|
506 let file = cm.lookup_char_pos(sp.lo()).file;
507 if file.name.is_macros() {
517 let error_id = (DiagnosticMessageId::StabilityId(issue), span_key, msg.clone());
518 let fresh = sess.one_time_diagnostics.borrow_mut().insert(error_id);
521 soft_handler(lint::builtin::SOFT_UNSTABLE, span, &msg)
524 &sess.parse_sess, feature, span, GateIssue::Library(issue), &msg
530 /// Checks whether an item marked with `deprecated(since="X")` is currently
531 /// deprecated (i.e., whether X is not greater than the current rustc version).
532 pub fn deprecation_in_effect(since: &str) -> bool {
533 fn parse_version(ver: &str) -> Vec<u32> {
534 // We ignore non-integer components of the version (e.g., "nightly").
535 ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
538 if let Some(rustc) = option_env!("CFG_RELEASE") {
539 let since: Vec<u32> = parse_version(since);
540 let rustc: Vec<u32> = parse_version(rustc);
541 // We simply treat invalid `since` attributes as relating to a previous
542 // Rust version, thus always displaying the warning.
543 if since.len() != 3 {
548 // By default, a deprecation warning applies to
549 // the current version of the compiler.
554 pub fn deprecation_suggestion(
555 diag: &mut DiagnosticBuilder<'_>, suggestion: Option<Symbol>, span: Span
557 if let Some(suggestion) = suggestion {
558 diag.span_suggestion(
560 "replace the use of the deprecated item",
561 suggestion.to_string(),
562 Applicability::MachineApplicable,
567 fn deprecation_message_common(message: String, reason: Option<Symbol>) -> String {
569 Some(reason) => format!("{}: {}", message, reason),
574 pub fn deprecation_message(depr: &Deprecation, path: &str) -> (String, &'static Lint) {
575 let message = format!("use of deprecated item '{}'", path);
576 (deprecation_message_common(message, depr.note), lint::builtin::DEPRECATED)
579 pub fn rustc_deprecation_message(depr: &RustcDeprecation, path: &str) -> (String, &'static Lint) {
580 let (message, lint) = if deprecation_in_effect(&depr.since.as_str()) {
581 (format!("use of deprecated item '{}'", path), lint::builtin::DEPRECATED)
583 (format!("use of item '{}' that will be deprecated in future version {}", path, depr.since),
584 lint::builtin::DEPRECATED_IN_FUTURE)
586 (deprecation_message_common(message, Some(depr.reason)), lint)
589 pub fn early_report_deprecation(
590 lint_buffer: &'a mut lint::LintBuffer,
592 suggestion: Option<Symbol>,
596 if in_derive_expansion(span) {
600 let diag = BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span);
601 lint_buffer.buffer_lint_with_diagnostic(lint, CRATE_NODE_ID, span, message, diag);
604 fn late_report_deprecation(
607 suggestion: Option<Symbol>,
613 if in_derive_expansion(span) {
617 let mut diag = tcx.struct_span_lint_hir(lint, hir_id, span, message);
618 if let hir::Node::Expr(_) = tcx.hir().get(hir_id) {
619 deprecation_suggestion(&mut diag, suggestion, span);
622 if hir_id == hir::DUMMY_HIR_ID {
623 span_bug!(span, "emitted a {} lint with dummy HIR id: {:?}", lint.name, def_id);
627 struct Checker<'tcx> {
631 /// Result of `TyCtxt::eval_stability`.
632 pub enum EvalResult {
633 /// We can use the item because it is stable or we provided the
634 /// corresponding feature gate.
636 /// We cannot use the item because it is unstable and we did not provide the
637 /// corresponding feature gate.
640 reason: Option<Symbol>,
641 issue: Option<NonZeroU32>,
644 /// The item does not have the `#[stable]` or `#[unstable]` marker assigned.
648 impl<'tcx> TyCtxt<'tcx> {
650 fn skip_stability_check_due_to_privacy(self, mut def_id: DefId) -> bool {
651 // Check if `def_id` is a trait method.
652 match self.def_kind(def_id) {
653 Some(DefKind::Method) |
654 Some(DefKind::AssocTy) |
655 Some(DefKind::AssocConst) => {
656 if let ty::TraitContainer(trait_def_id) = self.associated_item(def_id).container {
657 // Trait methods do not declare visibility (even
658 // for visibility info in cstore). Use containing
659 // trait instead, so methods of `pub` traits are
660 // themselves considered `pub`.
661 def_id = trait_def_id;
667 let visibility = self.visibility(def_id);
670 // Must check stability for `pub` items.
671 ty::Visibility::Public => false,
673 // These are not visible outside crate; therefore
674 // stability markers are irrelevant, if even present.
675 ty::Visibility::Restricted(..) |
676 ty::Visibility::Invisible => true,
680 /// Evaluates the stability of an item.
682 /// Returns `EvalResult::Allow` if the item is stable, or unstable but the corresponding
683 /// `#![feature]` has been provided. Returns `EvalResult::Deny` which describes the offending
684 /// unstable feature otherwise.
686 /// If `id` is `Some(_)`, this function will also check if the item at `def_id` has been
687 /// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
689 pub fn eval_stability(self, def_id: DefId, id: Option<HirId>, span: Span) -> EvalResult {
690 // Deprecated attributes apply in-crate and cross-crate.
691 if let Some(id) = id {
692 if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
693 let parent_def_id = self.hir().local_def_id(
694 self.hir().get_parent_item(id));
695 let skip = self.lookup_deprecation_entry(parent_def_id)
696 .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
699 let (message, lint) =
700 deprecation_message(&depr_entry.attr, &self.def_path_str(def_id));
701 late_report_deprecation(self, &message, None, lint, span, def_id, id);
706 let is_staged_api = self.lookup_stability(DefId {
707 index: CRATE_DEF_INDEX,
711 return EvalResult::Allow;
714 let stability = self.lookup_stability(def_id);
716 inspecting def_id={:?} span={:?} of stability={:?}", def_id, span, stability);
718 if let Some(id) = id {
719 if let Some(stability) = stability {
720 if let Some(depr) = &stability.rustc_depr {
721 let (message, lint) =
722 rustc_deprecation_message(depr, &self.def_path_str(def_id));
723 late_report_deprecation(
724 self, &message, depr.suggestion, lint, span, def_id, id
730 // Only the cross-crate scenario matters when checking unstable APIs
731 let cross_crate = !def_id.is_local();
733 return EvalResult::Allow;
736 // Issue #38412: private items lack stability markers.
737 if self.skip_stability_check_due_to_privacy(def_id) {
738 return EvalResult::Allow;
743 level: attr::Unstable { reason, issue, is_soft }, feature, ..
745 if span.allows_unstable(feature) {
746 debug!("stability: skipping span={:?} since it is internal", span);
747 return EvalResult::Allow;
749 if self.stability().active_features.contains(&feature) {
750 return EvalResult::Allow;
753 // When we're compiling the compiler itself we may pull in
754 // crates from crates.io, but those crates may depend on other
755 // crates also pulled in from crates.io. We want to ideally be
756 // able to compile everything without requiring upstream
757 // modifications, so in the case that this looks like a
758 // `rustc_private` crate (e.g., a compiler crate) and we also have
759 // the `-Z force-unstable-if-unmarked` flag present (we're
760 // compiling a compiler crate), then let this missing feature
762 if feature == sym::rustc_private && issue == NonZeroU32::new(27812) {
763 if self.sess.opts.debugging_opts.force_unstable_if_unmarked {
764 return EvalResult::Allow;
768 EvalResult::Deny { feature, reason, issue, is_soft }
771 // Stable APIs are always ok to call and deprecated APIs are
772 // handled by the lint emitting logic above.
781 /// Checks if an item is stable or error out.
783 /// If the item defined by `def_id` is unstable and the corresponding `#![feature]` does not
784 /// exist, emits an error.
786 /// Additionally, this function will also check if the item is deprecated. If so, and `id` is
787 /// not `None`, a deprecated lint attached to `id` will be emitted.
788 pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
790 |lint, span, msg: &_| self.lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg);
791 match self.eval_stability(def_id, id, span) {
792 EvalResult::Allow => {}
793 EvalResult::Deny { feature, reason, issue, is_soft } =>
794 report_unstable(self.sess, feature, reason, issue, is_soft, span, soft_handler),
795 EvalResult::Unmarked => {
796 // The API could be uncallable for other reasons, for example when a private module
798 self.sess.delay_span_bug(span, &format!("encountered unmarked API: {:?}", def_id));
804 impl Visitor<'tcx> for Checker<'tcx> {
805 /// Because stability levels are scoped lexically, we want to walk
806 /// nested items in the context of the outer item, so enable
808 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
809 NestedVisitorMap::OnlyBodies(&self.tcx.hir())
812 fn visit_item(&mut self, item: &'tcx hir::Item) {
814 hir::ItemKind::ExternCrate(_) => {
815 // compiler-generated `extern crate` items have a dummy span.
816 if item.span.is_dummy() { return }
818 let def_id = self.tcx.hir().local_def_id(item.hir_id);
819 let cnum = match self.tcx.extern_mod_stmt_cnum(def_id) {
823 let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
824 self.tcx.check_stability(def_id, Some(item.hir_id), item.span);
827 // For implementations of traits, check the stability of each item
828 // individually as it's possible to have a stable trait with unstable
830 hir::ItemKind::Impl(.., Some(ref t), _, ref impl_item_refs) => {
831 if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
832 for impl_item_ref in impl_item_refs {
833 let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
834 let trait_item_def_id = self.tcx.associated_items(trait_did)
835 .find(|item| item.ident.name == impl_item.ident.name)
836 .map(|item| item.def_id);
837 if let Some(def_id) = trait_item_def_id {
838 // Pass `None` to skip deprecation warnings.
839 self.tcx.check_stability(def_id, None, impl_item.span);
845 // There's no good place to insert stability check for non-Copy unions,
846 // so semi-randomly perform it here in stability.rs
847 hir::ItemKind::Union(..) if !self.tcx.features().untagged_unions => {
848 let def_id = self.tcx.hir().local_def_id(item.hir_id);
849 let adt_def = self.tcx.adt_def(def_id);
850 let ty = self.tcx.type_of(def_id);
852 if adt_def.has_dtor(self.tcx) {
853 emit_feature_err(&self.tcx.sess.parse_sess,
854 sym::untagged_unions, item.span, GateIssue::Language,
855 "unions with `Drop` implementations are unstable");
857 let param_env = self.tcx.param_env(def_id);
858 if !param_env.can_type_implement_copy(self.tcx, ty).is_ok() {
859 emit_feature_err(&self.tcx.sess.parse_sess,
860 sym::untagged_unions, item.span, GateIssue::Language,
861 "unions with non-`Copy` fields are unstable");
868 intravisit::walk_item(self, item);
871 fn visit_path(&mut self, path: &'tcx hir::Path, id: hir::HirId) {
872 if let Some(def_id) = path.res.opt_def_id() {
873 self.tcx.check_stability(def_id, Some(id), path.span)
875 intravisit::walk_path(self, path)
879 impl<'tcx> TyCtxt<'tcx> {
880 pub fn lookup_deprecation(self, id: DefId) -> Option<Deprecation> {
881 self.lookup_deprecation_entry(id).map(|depr| depr.attr)
885 /// Given the list of enabled features that were not language features (i.e., that
886 /// were expected to be library features), and the list of features used from
887 /// libraries, identify activated features that don't exist and error about them.
888 pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
889 let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
891 if tcx.stability().staged_api[&LOCAL_CRATE] {
892 let krate = tcx.hir().krate();
893 let mut missing = MissingStabilityAnnotations {
897 missing.check_missing_stability(hir::CRATE_HIR_ID, krate.span, "crate");
898 intravisit::walk_crate(&mut missing, krate);
899 krate.visit_all_item_likes(&mut missing.as_deep_visitor());
902 let declared_lang_features = &tcx.features().declared_lang_features;
903 let mut lang_features = FxHashSet::default();
904 for &(feature, span, since) in declared_lang_features {
905 if let Some(since) = since {
906 // Warn if the user has enabled an already-stable lang feature.
907 unnecessary_stable_feature_lint(tcx, span, feature, since);
909 if !lang_features.insert(feature) {
910 // Warn if the user enables a lang feature multiple times.
911 duplicate_feature_err(tcx.sess, span, feature);
915 let declared_lib_features = &tcx.features().declared_lib_features;
916 let mut remaining_lib_features = FxHashMap::default();
917 for (feature, span) in declared_lib_features {
918 if remaining_lib_features.contains_key(&feature) {
919 // Warn if the user enables a lib feature multiple times.
920 duplicate_feature_err(tcx.sess, *span, *feature);
922 remaining_lib_features.insert(feature, span.clone());
924 // `stdbuild` has special handling for `libc`, so we need to
925 // recognise the feature when building std.
926 // Likewise, libtest is handled specially, so `test` isn't
927 // available as we'd like it to be.
928 // FIXME: only remove `libc` when `stdbuild` is active.
929 // FIXME: remove special casing for `test`.
930 remaining_lib_features.remove(&Symbol::intern("libc"));
931 remaining_lib_features.remove(&sym::test);
934 |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {
935 for &(feature, since) in defined_features {
936 if let Some(since) = since {
937 if let Some(span) = remaining_lib_features.get(&feature) {
938 // Warn if the user has enabled an already-stable lib feature.
939 unnecessary_stable_feature_lint(tcx, *span, feature, since);
942 remaining_lib_features.remove(&feature);
943 if remaining_lib_features.is_empty() {
949 // We always collect the lib features declared in the current crate, even if there are
950 // no unknown features, because the collection also does feature attribute validation.
951 let local_defined_features = tcx.lib_features().to_vec();
952 if !remaining_lib_features.is_empty() {
953 check_features(&mut remaining_lib_features, &local_defined_features);
955 for &cnum in &*tcx.crates() {
956 if remaining_lib_features.is_empty() {
959 check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
963 for (feature, span) in remaining_lib_features {
964 struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
967 // FIXME(#44232): the `used_features` table no longer exists, so we
968 // don't lint about unused features. We should reenable this one day!
971 fn unnecessary_stable_feature_lint(
977 tcx.lint_hir(lint::builtin::STABLE_FEATURES,
980 &format!("the feature `{}` has been stable since {} and no longer requires \
981 an attribute to enable", feature, since));
984 fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
985 struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)