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 rustc_feature::GateIssue;
17 use syntax::symbol::{Symbol, sym};
18 use syntax_pos::{Span, MultiSpan};
19 use syntax::ast::{Attribute, CRATE_NODE_ID};
20 use syntax::errors::Applicability;
21 use syntax::feature_gate::{feature_err, feature_err_issue};
22 use syntax::attr::{self, Stability, Deprecation, RustcDeprecation};
23 use crate::ty::{self, TyCtxt};
24 use crate::util::nodemap::{FxHashSet, FxHashMap};
26 use std::cmp::Ordering;
27 use std::mem::replace;
28 use std::num::NonZeroU32;
30 use rustc_error_codes::*;
33 #[derive(PartialEq, Clone, Copy, Debug)]
34 pub enum StabilityLevel {
40 pub fn from_attr_level(level: &attr::StabilityLevel) -> Self {
41 if level.is_stable() { Stable } else { Unstable }
47 // Annotation is required if not inherited from unstable parents
49 // Annotation is useless, reject it
51 // Annotation itself is useless, but it can be propagated to children
55 /// An entry in the `depr_map`.
56 #[derive(Clone, HashStable)]
57 pub struct DeprecationEntry {
58 /// The metadata of the attribute associated with this entry.
59 pub attr: Deprecation,
60 /// The `DefId` where the attr was originally attached. `None` for non-local
62 origin: Option<HirId>,
65 impl DeprecationEntry {
66 fn local(attr: Deprecation, id: HirId) -> DeprecationEntry {
73 pub fn external(attr: Deprecation) -> DeprecationEntry {
80 pub fn same_origin(&self, other: &DeprecationEntry) -> bool {
81 match (self.origin, other.origin) {
82 (Some(o1), Some(o2)) => o1 == o2,
88 /// 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 // A private tree-walker for producing an Index.
104 struct Annotator<'a, 'tcx> {
106 index: &'a mut Index<'tcx>,
107 parent_stab: Option<&'tcx Stability>,
108 parent_depr: Option<DeprecationEntry>,
112 impl<'a, 'tcx> Annotator<'a, 'tcx> {
113 // Determine the stability for a node based on its attributes and inherited
114 // stability. The stability is recorded in the index and used as the parent.
115 fn annotate<F>(&mut self, hir_id: HirId, attrs: &[Attribute],
116 item_sp: Span, kind: AnnotationKind, visit_children: F)
117 where F: FnOnce(&mut Self)
119 if self.tcx.features().staged_api {
120 // This crate explicitly wants staged API.
121 debug!("annotate(id = {:?}, attrs = {:?})", hir_id, attrs);
122 if let Some(..) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
123 self.tcx.sess.span_err(item_sp, "`#[deprecated]` cannot be used in staged API; \
124 use `#[rustc_deprecated]` instead");
126 if let Some(mut stab) = attr::find_stability(&self.tcx.sess.parse_sess,
128 // Error if prohibited, or can't inherit anything from a container.
129 if kind == AnnotationKind::Prohibited ||
130 (kind == AnnotationKind::Container &&
131 stab.level.is_stable() &&
132 stab.rustc_depr.is_none()) {
133 self.tcx.sess.span_err(item_sp, "This stability annotation is useless");
136 debug!("annotate: found {:?}", stab);
137 // If parent is deprecated and we're not, inherit this by merging
138 // deprecated_since and its reason.
139 if let Some(parent_stab) = self.parent_stab {
140 if parent_stab.rustc_depr.is_some() && stab.rustc_depr.is_none() {
141 stab.rustc_depr = parent_stab.rustc_depr.clone()
145 let stab = self.tcx.intern_stability(stab);
147 // Check if deprecated_since < stable_since. If it is,
148 // this is *almost surely* an accident.
149 if let (&Some(attr::RustcDeprecation {since: dep_since, ..}),
150 &attr::Stable {since: stab_since}) = (&stab.rustc_depr, &stab.level) {
151 // Explicit version of iter::order::lt to handle parse errors properly
152 for (dep_v, stab_v) in dep_since.as_str()
154 .zip(stab_since.as_str().split('.'))
156 if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
157 match dep_v.cmp(&stab_v) {
159 self.tcx.sess.span_err(item_sp, "An API can't be stabilized \
160 after it is deprecated");
163 Ordering::Equal => continue,
164 Ordering::Greater => break,
167 // Act like it isn't less because the question is now nonsensical,
168 // and this makes us not do anything else interesting.
169 self.tcx.sess.span_err(item_sp, "Invalid stability or deprecation \
176 self.index.stab_map.insert(hir_id, stab);
178 let orig_parent_stab = replace(&mut self.parent_stab, Some(stab));
179 visit_children(self);
180 self.parent_stab = orig_parent_stab;
182 debug!("annotate: not found, parent = {:?}", self.parent_stab);
183 if let Some(stab) = self.parent_stab {
184 if stab.level.is_unstable() {
185 self.index.stab_map.insert(hir_id, stab);
188 visit_children(self);
191 // Emit errors for non-staged-api crates.
193 let name = attr.name_or_empty();
194 if [sym::unstable, sym::stable, sym::rustc_deprecated].contains(&name) {
195 attr::mark_used(attr);
200 "stability attributes may not be used outside of the standard library",
205 // Propagate unstability. This can happen even for non-staged-api crates in case
206 // -Zforce-unstable-if-unmarked is set.
207 if let Some(stab) = self.parent_stab {
208 if stab.level.is_unstable() {
209 self.index.stab_map.insert(hir_id, stab);
213 if let Some(depr) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
214 if kind == AnnotationKind::Prohibited {
215 self.tcx.sess.span_err(item_sp, "This deprecation annotation is useless");
218 // `Deprecation` is just two pointers, no need to intern it
219 let depr_entry = DeprecationEntry::local(depr, hir_id);
220 self.index.depr_map.insert(hir_id, depr_entry.clone());
222 let orig_parent_depr = replace(&mut self.parent_depr,
224 visit_children(self);
225 self.parent_depr = orig_parent_depr;
226 } else if let Some(parent_depr) = self.parent_depr.clone() {
227 self.index.depr_map.insert(hir_id, parent_depr);
228 visit_children(self);
230 visit_children(self);
236 impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
237 /// Because stability levels are scoped lexically, we want to walk
238 /// nested items in the context of the outer item, so enable
240 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
241 NestedVisitorMap::All(&self.tcx.hir())
244 fn visit_item(&mut self, i: &'tcx Item) {
245 let orig_in_trait_impl = self.in_trait_impl;
246 let mut kind = AnnotationKind::Required;
248 // Inherent impls and foreign modules serve only as containers for other items,
249 // they don't have their own stability. They still can be annotated as unstable
250 // and propagate this unstability to children, but this annotation is completely
251 // optional. They inherit stability from their parents when unannotated.
252 hir::ItemKind::Impl(.., None, _, _) | hir::ItemKind::ForeignMod(..) => {
253 self.in_trait_impl = false;
254 kind = AnnotationKind::Container;
256 hir::ItemKind::Impl(.., Some(_), _, _) => {
257 self.in_trait_impl = true;
259 hir::ItemKind::Struct(ref sd, _) => {
260 if let Some(ctor_hir_id) = sd.ctor_hir_id() {
261 self.annotate(ctor_hir_id, &i.attrs, i.span, AnnotationKind::Required, |_| {})
267 self.annotate(i.hir_id, &i.attrs, i.span, kind, |v| {
268 intravisit::walk_item(v, i)
270 self.in_trait_impl = orig_in_trait_impl;
273 fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem) {
274 self.annotate(ti.hir_id, &ti.attrs, ti.span, AnnotationKind::Required, |v| {
275 intravisit::walk_trait_item(v, ti);
279 fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
280 let kind = if self.in_trait_impl {
281 AnnotationKind::Prohibited
283 AnnotationKind::Required
285 self.annotate(ii.hir_id, &ii.attrs, ii.span, kind, |v| {
286 intravisit::walk_impl_item(v, ii);
290 fn visit_variant(&mut self, var: &'tcx Variant, g: &'tcx Generics, item_id: HirId) {
291 self.annotate(var.id, &var.attrs, var.span, AnnotationKind::Required,
293 if let Some(ctor_hir_id) = var.data.ctor_hir_id() {
294 v.annotate(ctor_hir_id, &var.attrs, var.span, AnnotationKind::Required,
298 intravisit::walk_variant(v, var, g, item_id)
302 fn visit_struct_field(&mut self, s: &'tcx StructField) {
303 self.annotate(s.hir_id, &s.attrs, s.span, AnnotationKind::Required, |v| {
304 intravisit::walk_struct_field(v, s);
308 fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem) {
309 self.annotate(i.hir_id, &i.attrs, i.span, AnnotationKind::Required, |v| {
310 intravisit::walk_foreign_item(v, i);
314 fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
315 self.annotate(md.hir_id, &md.attrs, md.span, AnnotationKind::Required, |_| {});
319 struct MissingStabilityAnnotations<'a, 'tcx> {
321 access_levels: &'a AccessLevels,
324 impl<'a, 'tcx> MissingStabilityAnnotations<'a, 'tcx> {
325 fn check_missing_stability(&self, hir_id: HirId, span: Span, name: &str) {
326 let stab = self.tcx.stability().local_stability(hir_id);
327 let is_error = !self.tcx.sess.opts.test &&
329 self.access_levels.is_reachable(hir_id);
331 self.tcx.sess.span_err(
333 &format!("{} has missing stability attribute", name),
339 impl<'a, 'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'a, 'tcx> {
340 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
341 NestedVisitorMap::OnlyBodies(&self.tcx.hir())
344 fn visit_item(&mut self, i: &'tcx Item) {
346 // Inherent impls and foreign modules serve only as containers for other items,
347 // they don't have their own stability. They still can be annotated as unstable
348 // and propagate this unstability to children, but this annotation is completely
349 // optional. They inherit stability from their parents when unannotated.
350 hir::ItemKind::Impl(.., None, _, _) | hir::ItemKind::ForeignMod(..) => {}
352 _ => self.check_missing_stability(i.hir_id, i.span, i.kind.descriptive_variant())
355 intravisit::walk_item(self, i)
358 fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem) {
359 self.check_missing_stability(ti.hir_id, ti.span, "item");
360 intravisit::walk_trait_item(self, ti);
363 fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
364 let impl_def_id = self.tcx.hir().local_def_id(
365 self.tcx.hir().get_parent_item(ii.hir_id));
366 if self.tcx.impl_trait_ref(impl_def_id).is_none() {
367 self.check_missing_stability(ii.hir_id, ii.span, "item");
369 intravisit::walk_impl_item(self, ii);
372 fn visit_variant(&mut self, var: &'tcx Variant, g: &'tcx Generics, item_id: HirId) {
373 self.check_missing_stability(var.id, var.span, "variant");
374 intravisit::walk_variant(self, var, g, item_id);
377 fn visit_struct_field(&mut self, s: &'tcx StructField) {
378 self.check_missing_stability(s.hir_id, s.span, "field");
379 intravisit::walk_struct_field(self, s);
382 fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem) {
383 self.check_missing_stability(i.hir_id, i.span, i.kind.descriptive_variant());
384 intravisit::walk_foreign_item(self, i);
387 fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
388 self.check_missing_stability(md.hir_id, md.span, "macro");
392 impl<'tcx> Index<'tcx> {
393 pub fn new(tcx: TyCtxt<'tcx>) -> Index<'tcx> {
395 tcx.sess.opts.debugging_opts.force_unstable_if_unmarked ||
396 tcx.features().staged_api;
397 let mut staged_api = FxHashMap::default();
398 staged_api.insert(LOCAL_CRATE, is_staged_api);
399 let mut index = Index {
401 stab_map: Default::default(),
402 depr_map: Default::default(),
403 active_features: Default::default(),
406 let active_lib_features = &tcx.features().declared_lib_features;
407 let active_lang_features = &tcx.features().declared_lang_features;
409 // Put the active features into a map for quick lookup.
410 index.active_features =
411 active_lib_features.iter().map(|&(ref s, ..)| s.clone())
412 .chain(active_lang_features.iter().map(|&(ref s, ..)| s.clone()))
416 let krate = tcx.hir().krate();
417 let mut annotator = Annotator {
422 in_trait_impl: false,
425 // If the `-Z force-unstable-if-unmarked` flag is passed then we provide
426 // a parent stability annotation which indicates that this is private
427 // with the `rustc_private` feature. This is intended for use when
428 // compiling librustc crates themselves so we can leverage crates.io
429 // while maintaining the invariant that all sysroot crates are unstable
430 // by default and are unable to be used.
431 if tcx.sess.opts.debugging_opts.force_unstable_if_unmarked {
432 let reason = "this crate is being loaded from the sysroot, an \
433 unstable location; did you mean to load this crate \
434 from crates.io via `Cargo.toml` instead?";
435 let stability = tcx.intern_stability(Stability {
436 level: attr::StabilityLevel::Unstable {
437 reason: Some(Symbol::intern(reason)),
438 issue: NonZeroU32::new(27812),
441 feature: sym::rustc_private,
443 const_stability: None,
445 allow_const_fn_ptr: false,
447 annotator.parent_stab = Some(stability);
450 annotator.annotate(hir::CRATE_HIR_ID,
453 AnnotationKind::Required,
454 |v| intravisit::walk_crate(v, krate));
459 pub fn local_stability(&self, id: HirId) -> Option<&'tcx Stability> {
460 self.stab_map.get(&id).cloned()
463 pub fn local_deprecation_entry(&self, id: HirId) -> Option<DeprecationEntry> {
464 self.depr_map.get(&id).cloned()
468 /// Cross-references the feature names of unstable APIs with enabled
469 /// features and possibly prints errors.
470 fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, module_def_id: DefId) {
471 tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx }.as_deep_visitor());
474 pub fn provide(providers: &mut Providers<'_>) {
475 *providers = Providers {
476 check_mod_unstable_api_usage,
481 pub fn report_unstable(
484 reason: Option<Symbol>,
485 issue: Option<NonZeroU32>,
488 soft_handler: impl FnOnce(&'static lint::Lint, Span, &str),
490 let msg = match reason {
491 Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
492 None => format!("use of unstable library feature '{}'", &feature)
495 let msp: MultiSpan = span.into();
496 let cm = &sess.parse_sess.source_map();
497 let span_key = msp.primary_span().and_then(|sp: Span|
499 let file = cm.lookup_char_pos(sp.lo()).file;
500 if file.name.is_macros() {
510 let error_id = (DiagnosticMessageId::StabilityId(issue), span_key, msg.clone());
511 let fresh = sess.one_time_diagnostics.borrow_mut().insert(error_id);
514 soft_handler(lint::builtin::SOFT_UNSTABLE, span, &msg)
516 feature_err_issue(&sess.parse_sess, feature, span, GateIssue::Library(issue), &msg)
522 /// Checks whether an item marked with `deprecated(since="X")` is currently
523 /// deprecated (i.e., whether X is not greater than the current rustc version).
524 pub fn deprecation_in_effect(since: &str) -> bool {
525 fn parse_version(ver: &str) -> Vec<u32> {
526 // We ignore non-integer components of the version (e.g., "nightly").
527 ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
530 if let Some(rustc) = option_env!("CFG_RELEASE") {
531 let since: Vec<u32> = parse_version(since);
532 let rustc: Vec<u32> = parse_version(rustc);
533 // We simply treat invalid `since` attributes as relating to a previous
534 // Rust version, thus always displaying the warning.
535 if since.len() != 3 {
540 // By default, a deprecation warning applies to
541 // the current version of the compiler.
546 pub fn deprecation_suggestion(
547 diag: &mut DiagnosticBuilder<'_>, suggestion: Option<Symbol>, span: Span
549 if let Some(suggestion) = suggestion {
550 diag.span_suggestion(
552 "replace the use of the deprecated item",
553 suggestion.to_string(),
554 Applicability::MachineApplicable,
559 fn deprecation_message_common(message: String, reason: Option<Symbol>) -> String {
561 Some(reason) => format!("{}: {}", message, reason),
566 pub fn deprecation_message(depr: &Deprecation, path: &str) -> (String, &'static Lint) {
567 let message = format!("use of deprecated item '{}'", path);
568 (deprecation_message_common(message, depr.note), lint::builtin::DEPRECATED)
571 pub fn rustc_deprecation_message(depr: &RustcDeprecation, path: &str) -> (String, &'static Lint) {
572 let (message, lint) = if deprecation_in_effect(&depr.since.as_str()) {
573 (format!("use of deprecated item '{}'", path), lint::builtin::DEPRECATED)
575 (format!("use of item '{}' that will be deprecated in future version {}", path, depr.since),
576 lint::builtin::DEPRECATED_IN_FUTURE)
578 (deprecation_message_common(message, Some(depr.reason)), lint)
581 pub fn early_report_deprecation(
582 lint_buffer: &'a mut lint::LintBuffer,
584 suggestion: Option<Symbol>,
588 if in_derive_expansion(span) {
592 let diag = BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span);
593 lint_buffer.buffer_lint_with_diagnostic(lint, CRATE_NODE_ID, span, message, diag);
596 fn late_report_deprecation(
599 suggestion: Option<Symbol>,
605 if in_derive_expansion(span) {
609 let mut diag = tcx.struct_span_lint_hir(lint, hir_id, span, message);
610 if let hir::Node::Expr(_) = tcx.hir().get(hir_id) {
611 deprecation_suggestion(&mut diag, suggestion, span);
614 if hir_id == hir::DUMMY_HIR_ID {
615 span_bug!(span, "emitted a {} lint with dummy HIR id: {:?}", lint.name, def_id);
619 struct Checker<'tcx> {
623 /// Result of `TyCtxt::eval_stability`.
624 pub enum EvalResult {
625 /// We can use the item because it is stable or we provided the
626 /// corresponding feature gate.
628 /// We cannot use the item because it is unstable and we did not provide the
629 /// corresponding feature gate.
632 reason: Option<Symbol>,
633 issue: Option<NonZeroU32>,
636 /// The item does not have the `#[stable]` or `#[unstable]` marker assigned.
640 impl<'tcx> TyCtxt<'tcx> {
642 fn skip_stability_check_due_to_privacy(self, mut def_id: DefId) -> bool {
643 // Check if `def_id` is a trait method.
644 match self.def_kind(def_id) {
645 Some(DefKind::Method) |
646 Some(DefKind::AssocTy) |
647 Some(DefKind::AssocConst) => {
648 if let ty::TraitContainer(trait_def_id) = self.associated_item(def_id).container {
649 // Trait methods do not declare visibility (even
650 // for visibility info in cstore). Use containing
651 // trait instead, so methods of `pub` traits are
652 // themselves considered `pub`.
653 def_id = trait_def_id;
659 let visibility = self.visibility(def_id);
662 // Must check stability for `pub` items.
663 ty::Visibility::Public => false,
665 // These are not visible outside crate; therefore
666 // stability markers are irrelevant, if even present.
667 ty::Visibility::Restricted(..) |
668 ty::Visibility::Invisible => true,
672 /// Evaluates the stability of an item.
674 /// Returns `EvalResult::Allow` if the item is stable, or unstable but the corresponding
675 /// `#![feature]` has been provided. Returns `EvalResult::Deny` which describes the offending
676 /// unstable feature otherwise.
678 /// If `id` is `Some(_)`, this function will also check if the item at `def_id` has been
679 /// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
681 pub fn eval_stability(self, def_id: DefId, id: Option<HirId>, span: Span) -> EvalResult {
682 // Deprecated attributes apply in-crate and cross-crate.
683 if let Some(id) = id {
684 if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
685 let parent_def_id = self.hir().local_def_id(
686 self.hir().get_parent_item(id));
687 let skip = self.lookup_deprecation_entry(parent_def_id)
688 .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
691 let (message, lint) =
692 deprecation_message(&depr_entry.attr, &self.def_path_str(def_id));
693 late_report_deprecation(self, &message, None, lint, span, def_id, id);
698 let is_staged_api = self.lookup_stability(DefId {
699 index: CRATE_DEF_INDEX,
703 return EvalResult::Allow;
706 let stability = self.lookup_stability(def_id);
708 inspecting def_id={:?} span={:?} of stability={:?}", def_id, span, stability);
710 if let Some(id) = id {
711 if let Some(stability) = stability {
712 if let Some(depr) = &stability.rustc_depr {
713 let (message, lint) =
714 rustc_deprecation_message(depr, &self.def_path_str(def_id));
715 late_report_deprecation(
716 self, &message, depr.suggestion, lint, span, def_id, id
722 // Only the cross-crate scenario matters when checking unstable APIs
723 let cross_crate = !def_id.is_local();
725 return EvalResult::Allow;
728 // Issue #38412: private items lack stability markers.
729 if self.skip_stability_check_due_to_privacy(def_id) {
730 return EvalResult::Allow;
735 level: attr::Unstable { reason, issue, is_soft }, feature, ..
737 if span.allows_unstable(feature) {
738 debug!("stability: skipping span={:?} since it is internal", span);
739 return EvalResult::Allow;
741 if self.stability().active_features.contains(&feature) {
742 return EvalResult::Allow;
745 // When we're compiling the compiler itself we may pull in
746 // crates from crates.io, but those crates may depend on other
747 // crates also pulled in from crates.io. We want to ideally be
748 // able to compile everything without requiring upstream
749 // modifications, so in the case that this looks like a
750 // `rustc_private` crate (e.g., a compiler crate) and we also have
751 // the `-Z force-unstable-if-unmarked` flag present (we're
752 // compiling a compiler crate), then let this missing feature
754 if feature == sym::rustc_private && issue == NonZeroU32::new(27812) {
755 if self.sess.opts.debugging_opts.force_unstable_if_unmarked {
756 return EvalResult::Allow;
760 EvalResult::Deny { feature, reason, issue, is_soft }
763 // Stable APIs are always ok to call and deprecated APIs are
764 // handled by the lint emitting logic above.
773 /// Checks if an item is stable or error out.
775 /// If the item defined by `def_id` is unstable and the corresponding `#![feature]` does not
776 /// exist, emits an error.
778 /// Additionally, this function will also check if the item is deprecated. If so, and `id` is
779 /// not `None`, a deprecated lint attached to `id` will be emitted.
780 pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
782 |lint, span, msg: &_| self.lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, msg);
783 match self.eval_stability(def_id, id, span) {
784 EvalResult::Allow => {}
785 EvalResult::Deny { feature, reason, issue, is_soft } =>
786 report_unstable(self.sess, feature, reason, issue, is_soft, span, soft_handler),
787 EvalResult::Unmarked => {
788 // The API could be uncallable for other reasons, for example when a private module
790 self.sess.delay_span_bug(span, &format!("encountered unmarked API: {:?}", def_id));
796 impl Visitor<'tcx> for Checker<'tcx> {
797 /// Because stability levels are scoped lexically, we want to walk
798 /// nested items in the context of the outer item, so enable
800 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
801 NestedVisitorMap::OnlyBodies(&self.tcx.hir())
804 fn visit_item(&mut self, item: &'tcx hir::Item) {
806 hir::ItemKind::ExternCrate(_) => {
807 // compiler-generated `extern crate` items have a dummy span.
808 if item.span.is_dummy() { return }
810 let def_id = self.tcx.hir().local_def_id(item.hir_id);
811 let cnum = match self.tcx.extern_mod_stmt_cnum(def_id) {
815 let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
816 self.tcx.check_stability(def_id, Some(item.hir_id), item.span);
819 // For implementations of traits, check the stability of each item
820 // individually as it's possible to have a stable trait with unstable
822 hir::ItemKind::Impl(.., Some(ref t), _, ref impl_item_refs) => {
823 if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
824 for impl_item_ref in impl_item_refs {
825 let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
826 let trait_item_def_id = self.tcx.associated_items(trait_did)
827 .find(|item| item.ident.name == impl_item.ident.name)
828 .map(|item| item.def_id);
829 if let Some(def_id) = trait_item_def_id {
830 // Pass `None` to skip deprecation warnings.
831 self.tcx.check_stability(def_id, None, impl_item.span);
837 // There's no good place to insert stability check for non-Copy unions,
838 // so semi-randomly perform it here in stability.rs
839 hir::ItemKind::Union(..) if !self.tcx.features().untagged_unions => {
840 let def_id = self.tcx.hir().local_def_id(item.hir_id);
841 let adt_def = self.tcx.adt_def(def_id);
842 let ty = self.tcx.type_of(def_id);
844 if adt_def.has_dtor(self.tcx) {
846 &self.tcx.sess.parse_sess, sym::untagged_unions, item.span,
847 "unions with `Drop` implementations are unstable"
851 let param_env = self.tcx.param_env(def_id);
852 if !param_env.can_type_implement_copy(self.tcx, ty).is_ok() {
854 &self.tcx.sess.parse_sess, sym::untagged_unions, item.span,
855 "unions with non-`Copy` fields are unstable"
864 intravisit::walk_item(self, item);
867 fn visit_path(&mut self, path: &'tcx hir::Path, id: hir::HirId) {
868 if let Some(def_id) = path.res.opt_def_id() {
869 self.tcx.check_stability(def_id, Some(id), path.span)
871 intravisit::walk_path(self, path)
875 impl<'tcx> TyCtxt<'tcx> {
876 pub fn lookup_deprecation(self, id: DefId) -> Option<Deprecation> {
877 self.lookup_deprecation_entry(id).map(|depr| depr.attr)
881 /// Given the list of enabled features that were not language features (i.e., that
882 /// were expected to be library features), and the list of features used from
883 /// libraries, identify activated features that don't exist and error about them.
884 pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
885 let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
887 if tcx.stability().staged_api[&LOCAL_CRATE] {
888 let krate = tcx.hir().krate();
889 let mut missing = MissingStabilityAnnotations {
893 missing.check_missing_stability(hir::CRATE_HIR_ID, krate.span, "crate");
894 intravisit::walk_crate(&mut missing, krate);
895 krate.visit_all_item_likes(&mut missing.as_deep_visitor());
898 let declared_lang_features = &tcx.features().declared_lang_features;
899 let mut lang_features = FxHashSet::default();
900 for &(feature, span, since) in declared_lang_features {
901 if let Some(since) = since {
902 // Warn if the user has enabled an already-stable lang feature.
903 unnecessary_stable_feature_lint(tcx, span, feature, since);
905 if !lang_features.insert(feature) {
906 // Warn if the user enables a lang feature multiple times.
907 duplicate_feature_err(tcx.sess, span, feature);
911 let declared_lib_features = &tcx.features().declared_lib_features;
912 let mut remaining_lib_features = FxHashMap::default();
913 for (feature, span) in declared_lib_features {
914 if remaining_lib_features.contains_key(&feature) {
915 // Warn if the user enables a lib feature multiple times.
916 duplicate_feature_err(tcx.sess, *span, *feature);
918 remaining_lib_features.insert(feature, span.clone());
920 // `stdbuild` has special handling for `libc`, so we need to
921 // recognise the feature when building std.
922 // Likewise, libtest is handled specially, so `test` isn't
923 // available as we'd like it to be.
924 // FIXME: only remove `libc` when `stdbuild` is active.
925 // FIXME: remove special casing for `test`.
926 remaining_lib_features.remove(&Symbol::intern("libc"));
927 remaining_lib_features.remove(&sym::test);
930 |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {
931 for &(feature, since) in defined_features {
932 if let Some(since) = since {
933 if let Some(span) = remaining_lib_features.get(&feature) {
934 // Warn if the user has enabled an already-stable lib feature.
935 unnecessary_stable_feature_lint(tcx, *span, feature, since);
938 remaining_lib_features.remove(&feature);
939 if remaining_lib_features.is_empty() {
945 // We always collect the lib features declared in the current crate, even if there are
946 // no unknown features, because the collection also does feature attribute validation.
947 let local_defined_features = tcx.lib_features().to_vec();
948 if !remaining_lib_features.is_empty() {
949 check_features(&mut remaining_lib_features, &local_defined_features);
951 for &cnum in &*tcx.crates() {
952 if remaining_lib_features.is_empty() {
955 check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
959 for (feature, span) in remaining_lib_features {
960 struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
963 // FIXME(#44232): the `used_features` table no longer exists, so we
964 // don't lint about unused features. We should reenable this one day!
967 fn unnecessary_stable_feature_lint(
973 tcx.lint_hir(lint::builtin::STABLE_FEATURES,
976 &format!("the feature `{}` has been stable since {} and no longer requires \
977 an attribute to enable", feature, since));
980 fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
981 struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)