src/librustc/middle/stability.rs

   1 //! A pass that annotates every item and method with its stability level,
   2 //! propagating default levels lexically from parent to children ast nodes.
   3
   4 pub use self::StabilityLevel::*;
   5
   6 use crate::lint::{self, Lint, in_derive_expansion};
   7 use crate::hir::{self, Item, Generics, StructField, Variant, HirId};
   8 use crate::hir::def::{Res, DefKind};
   9 use crate::hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, LOCAL_CRATE};
  10 use crate::hir::intravisit::{self, Visitor, NestedVisitorMap};
  11 use crate::ty::query::Providers;
  12 use crate::middle::privacy::AccessLevels;
  13 use crate::session::{DiagnosticMessageId, Session};
  14 use syntax::symbol::{Symbol, sym};
  15 use syntax_pos::{Span, MultiSpan};
  16 use syntax::ast::Attribute;
  17 use syntax::errors::Applicability;
  18 use syntax::feature_gate::{GateIssue, emit_feature_err};
  19 use syntax::attr::{self, Stability, Deprecation};
  20 use crate::ty::{self, TyCtxt};
  21 use crate::util::nodemap::{FxHashSet, FxHashMap};
  22
  23 use std::mem::replace;
  24 use std::cmp::Ordering;
  25
  26 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Clone, Copy, Debug, Eq, Hash)]
  27 pub enum StabilityLevel {
  28     Unstable,
  29     Stable,
  30 }
  31
  32 impl StabilityLevel {
  33     pub fn from_attr_level(level: &attr::StabilityLevel) -> Self {
  34         if level.is_stable() { Stable } else { Unstable }
  35     }
  36 }
  37
  38 #[derive(PartialEq)]
  39 enum AnnotationKind {
  40     // Annotation is required if not inherited from unstable parents
  41     Required,
  42     // Annotation is useless, reject it
  43     Prohibited,
  44     // Annotation itself is useless, but it can be propagated to children
  45     Container,
  46 }
  47
  48 /// An entry in the `depr_map`.
  49 #[derive(Clone)]
  50 pub struct DeprecationEntry {
  51     /// The metadata of the attribute associated with this entry.
  52     pub attr: Deprecation,
  53     /// The `DefId` where the attr was originally attached. `None` for non-local
  54     /// `DefId`'s.
  55     origin: Option<HirId>,
  56 }
  57
  58 impl_stable_hash_for!(struct self::DeprecationEntry {
  59     attr,
  60     origin
  61 });
  62
  63 impl DeprecationEntry {
  64     fn local(attr: Deprecation, id: HirId) -> DeprecationEntry {
  65         DeprecationEntry {
  66             attr,
  67             origin: Some(id),
  68         }
  69     }
  70
  71     pub fn external(attr: Deprecation) -> DeprecationEntry {
  72         DeprecationEntry {
  73             attr,
  74             origin: None,
  75         }
  76     }
  77
  78     pub fn same_origin(&self, other: &DeprecationEntry) -> bool {
  79         match (self.origin, other.origin) {
  80             (Some(o1), Some(o2)) => o1 == o2,
  81             _ => false
  82         }
  83     }
  84 }
  85
  86 /// A stability index, giving the stability level for items and methods.
  87 pub struct Index<'tcx> {
  88     /// This is mostly a cache, except the stabilities of local items
  89     /// are filled by the annotator.
  90     stab_map: FxHashMap<HirId, &'tcx Stability>,
  91     depr_map: FxHashMap<HirId, DeprecationEntry>,
  92
  93     /// Maps for each crate whether it is part of the staged API.
  94     staged_api: FxHashMap<CrateNum, bool>,
  95
  96     /// Features enabled for this crate.
  97     active_features: FxHashSet<Symbol>,
  98 }
  99
 100 impl_stable_hash_for!(struct self::Index<'tcx> {
 101     stab_map,
 102     depr_map,
 103     staged_api,
 104     active_features
 105 });
 106
 107 // A private tree-walker for producing an Index.
 108 struct Annotator<'a, 'tcx: 'a> {
 109     tcx: TyCtxt<'tcx, 'tcx>,
 110     index: &'a mut Index<'tcx>,
 111     parent_stab: Option<&'tcx Stability>,
 112     parent_depr: Option<DeprecationEntry>,
 113     in_trait_impl: bool,
 114 }
 115
 116 impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
 117     // Determine the stability for a node based on its attributes and inherited
 118     // stability. The stability is recorded in the index and used as the parent.
 119     fn annotate<F>(&mut self, hir_id: HirId, attrs: &[Attribute],
 120                    item_sp: Span, kind: AnnotationKind, visit_children: F)
 121         where F: FnOnce(&mut Self)
 122     {
 123         if self.tcx.features().staged_api {
 124             // This crate explicitly wants staged API.
 125             debug!("annotate(id = {:?}, attrs = {:?})", hir_id, attrs);
 126             if let Some(..) = attr::find_deprecation(&self.tcx.sess.parse_sess, attrs, item_sp) {
 127                 self.tcx.sess.span_err(item_sp, "`#[deprecated]` cannot be used in staged API; \
 128                                                  use `#[rustc_deprecated]` instead");
 129             }
 130             if let Some(mut stab) = attr::find_stability(&self.tcx.sess.parse_sess,
 131                                                          attrs, item_sp) {
 132                 // Error if prohibited, or can't inherit anything from a container.
 133                 if kind == AnnotationKind::Prohibited ||
 134                    (kind == AnnotationKind::Container &&
 135                     stab.level.is_stable() &&
 136                     stab.rustc_depr.is_none()) {
 137                     self.tcx.sess.span_err(item_sp, "This stability annotation is useless");
 138                 }
 139
 140                 debug!("annotate: found {:?}", stab);
 141                 // If parent is deprecated and we're not, inherit this by merging
 142                 // deprecated_since and its reason.
 143                 if let Some(parent_stab) = self.parent_stab {
 144                     if parent_stab.rustc_depr.is_some() && stab.rustc_depr.is_none() {
 145                         stab.rustc_depr = parent_stab.rustc_depr.clone()
 146                     }
 147                 }
 148
 149                 let stab = self.tcx.intern_stability(stab);
 150
 151                 // Check if deprecated_since < stable_since. If it is,
 152                 // this is *almost surely* an accident.
 153                 if let (&Some(attr::RustcDeprecation {since: dep_since, ..}),
 154                         &attr::Stable {since: stab_since}) = (&stab.rustc_depr, &stab.level) {
 155                     // Explicit version of iter::order::lt to handle parse errors properly
 156                     for (dep_v, stab_v) in dep_since.as_str()
 157                                                     .split('.')
 158                                                     .zip(stab_since.as_str().split('.'))
 159                     {
 160                         if let (Ok(dep_v), Ok(stab_v)) = (dep_v.parse::<u64>(), stab_v.parse()) {
 161                             match dep_v.cmp(&stab_v) {
 162                                 Ordering::Less => {
 163                                     self.tcx.sess.span_err(item_sp, "An API can't be stabilized \
 164                                                                      after it is deprecated");
 165                                     break
 166                                 }
 167                                 Ordering::Equal => continue,
 168                                 Ordering::Greater => break,
 169                             }
 170                         } else {
 171                             // Act like it isn't less because the question is now nonsensical,
 172                             // and this makes us not do anything else interesting.
 173                             self.tcx.sess.span_err(item_sp, "Invalid stability or deprecation \
 174                                                              version found");
 175                             break
 176                         }
 177                     }
 178                 }
 179
 180                 self.index.stab_map.insert(hir_id, stab);
 181
 182                 let orig_parent_stab = replace(&mut self.parent_stab, Some(stab));
 183                 visit_children(self);
 184                 self.parent_stab = orig_parent_stab;
 185             } else {
 186                 debug!("annotate: not found, parent = {:?}", self.parent_stab);
 187                 if let Some(stab) = self.parent_stab {
 188                     if stab.level.is_unstable() {
 189                         self.index.stab_map.insert(hir_id, stab);
 190                     }
 191                 }
 192                 visit_children(self);
 193             }
 194         } else {
 195             // Emit errors for non-staged-api crates.
 196             for attr in attrs {
 197                 let name = attr.name_or_empty();
 198                 if [sym::unstable, sym::stable, sym::rustc_deprecated].contains(&name) {
 199                     attr::mark_used(attr);
 200                     self.tcx.sess.span_err(attr.span, "stability attributes may not be used \
 201                                                         outside of the standard library");
 202                 }
 203             }
 204
 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);
 210                 }
 211             }
 212
 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");
 216                 }
 217
 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());
 221
 222                 let orig_parent_depr = replace(&mut self.parent_depr,
 223                                                Some(depr_entry));
 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);
 229             } else {
 230                 visit_children(self);
 231             }
 232         }
 233     }
 234 }
 235
 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
 239     /// deep-walking.
 240     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 241         NestedVisitorMap::All(&self.tcx.hir())
 242     }
 243
 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;
 247         match i.node {
 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;
 255             }
 256             hir::ItemKind::Impl(.., Some(_), _, _) => {
 257                 self.in_trait_impl = true;
 258             }
 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, |_| {})
 262                 }
 263             }
 264             _ => {}
 265         }
 266
 267         self.annotate(i.hir_id, &i.attrs, i.span, kind, |v| {
 268             intravisit::walk_item(v, i)
 269         });
 270         self.in_trait_impl = orig_in_trait_impl;
 271     }
 272
 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);
 276         });
 277     }
 278
 279     fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
 280         let kind = if self.in_trait_impl {
 281             AnnotationKind::Prohibited
 282         } else {
 283             AnnotationKind::Required
 284         };
 285         self.annotate(ii.hir_id, &ii.attrs, ii.span, kind, |v| {
 286             intravisit::walk_impl_item(v, ii);
 287         });
 288     }
 289
 290     fn visit_variant(&mut self, var: &'tcx Variant, g: &'tcx Generics, item_id: HirId) {
 291         self.annotate(var.node.id, &var.node.attrs, var.span, AnnotationKind::Required,
 292             |v| {
 293                 if let Some(ctor_hir_id) = var.node.data.ctor_hir_id() {
 294                     v.annotate(ctor_hir_id, &var.node.attrs, var.span, AnnotationKind::Required,
 295                                |_| {});
 296                 }
 297
 298                 intravisit::walk_variant(v, var, g, item_id)
 299             })
 300     }
 301
 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);
 305         });
 306     }
 307
 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);
 311         });
 312     }
 313
 314     fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
 315         self.annotate(md.hir_id, &md.attrs, md.span, AnnotationKind::Required, |_| {});
 316     }
 317 }
 318
 319 struct MissingStabilityAnnotations<'a, 'tcx: 'a> {
 320     tcx: TyCtxt<'tcx, 'tcx>,
 321     access_levels: &'a AccessLevels,
 322 }
 323
 324 impl<'a, 'tcx: 'a> 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 &&
 328                         stab.is_none() &&
 329                         self.access_levels.is_reachable(hir_id);
 330         if is_error {
 331             self.tcx.sess.span_err(
 332                 span,
 333                 &format!("{} has missing stability attribute", name),
 334             );
 335         }
 336     }
 337 }
 338
 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())
 342     }
 343
 344     fn visit_item(&mut self, i: &'tcx Item) {
 345         match i.node {
 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(..) => {}
 351
 352             _ => self.check_missing_stability(i.hir_id, i.span, i.node.descriptive_variant())
 353         }
 354
 355         intravisit::walk_item(self, i)
 356     }
 357
 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);
 361     }
 362
 363     fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem) {
 364         let impl_def_id = self.tcx.hir().local_def_id_from_hir_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");
 368         }
 369         intravisit::walk_impl_item(self, ii);
 370     }
 371
 372     fn visit_variant(&mut self, var: &'tcx Variant, g: &'tcx Generics, item_id: HirId) {
 373         self.check_missing_stability(var.node.id, var.span, "variant");
 374         intravisit::walk_variant(self, var, g, item_id);
 375     }
 376
 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);
 380     }
 381
 382     fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem) {
 383         self.check_missing_stability(i.hir_id, i.span, i.node.descriptive_variant());
 384         intravisit::walk_foreign_item(self, i);
 385     }
 386
 387     fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef) {
 388         self.check_missing_stability(md.hir_id, md.span, "macro");
 389     }
 390 }
 391
 392 impl<'tcx> Index<'tcx> {
 393     pub fn new(tcx: TyCtxt<'tcx, 'tcx>) -> Index<'tcx> {
 394         let is_staged_api =
 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 {
 400             staged_api,
 401             stab_map: Default::default(),
 402             depr_map: Default::default(),
 403             active_features: Default::default(),
 404         };
 405
 406         let active_lib_features = &tcx.features().declared_lib_features;
 407         let active_lang_features = &tcx.features().declared_lang_features;
 408
 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()))
 413             .collect();
 414
 415         {
 416             let krate = tcx.hir().krate();
 417             let mut annotator = Annotator {
 418                 tcx,
 419                 index: &mut index,
 420                 parent_stab: None,
 421                 parent_depr: None,
 422                 in_trait_impl: false,
 423             };
 424
 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: 27812,
 439                     },
 440                     feature: sym::rustc_private,
 441                     rustc_depr: None,
 442                     const_stability: None,
 443                     promotable: false,
 444                     allow_const_fn_ptr: false,
 445                 });
 446                 annotator.parent_stab = Some(stability);
 447             }
 448
 449             annotator.annotate(hir::CRATE_HIR_ID,
 450                                &krate.attrs,
 451                                krate.span,
 452                                AnnotationKind::Required,
 453                                |v| intravisit::walk_crate(v, krate));
 454         }
 455         return index
 456     }
 457
 458     pub fn local_stability(&self, id: HirId) -> Option<&'tcx Stability> {
 459         self.stab_map.get(&id).cloned()
 460     }
 461
 462     pub fn local_deprecation_entry(&self, id: HirId) -> Option<DeprecationEntry> {
 463         self.depr_map.get(&id).cloned()
 464     }
 465 }
 466
 467 /// Cross-references the feature names of unstable APIs with enabled
 468 /// features and possibly prints errors.
 469 fn check_mod_unstable_api_usage<'tcx>(tcx: TyCtxt<'tcx, 'tcx>, module_def_id: DefId) {
 470     tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx }.as_deep_visitor());
 471 }
 472
 473 pub fn provide(providers: &mut Providers<'_>) {
 474     *providers = Providers {
 475         check_mod_unstable_api_usage,
 476         ..*providers
 477     };
 478 }
 479
 480 /// Checks whether an item marked with `deprecated(since="X")` is currently
 481 /// deprecated (i.e., whether X is not greater than the current rustc version).
 482 pub fn deprecation_in_effect(since: &str) -> bool {
 483     fn parse_version(ver: &str) -> Vec<u32> {
 484         // We ignore non-integer components of the version (e.g., "nightly").
 485         ver.split(|c| c == '.' || c == '-').flat_map(|s| s.parse()).collect()
 486     }
 487
 488     if let Some(rustc) = option_env!("CFG_RELEASE") {
 489         let since: Vec<u32> = parse_version(since);
 490         let rustc: Vec<u32> = parse_version(rustc);
 491         // We simply treat invalid `since` attributes as relating to a previous
 492         // Rust version, thus always displaying the warning.
 493         if since.len() != 3 {
 494             return true;
 495         }
 496         since <= rustc
 497     } else {
 498         // By default, a deprecation warning applies to
 499         // the current version of the compiler.
 500         true
 501     }
 502 }
 503
 504 struct Checker<'tcx> {
 505     tcx: TyCtxt<'tcx, 'tcx>,
 506 }
 507
 508 /// Result of `TyCtxt::eval_stability`.
 509 pub enum EvalResult {
 510     /// We can use the item because it is stable or we provided the
 511     /// corresponding feature gate.
 512     Allow,
 513     /// We cannot use the item because it is unstable and we did not provide the
 514     /// corresponding feature gate.
 515     Deny {
 516         feature: Symbol,
 517         reason: Option<Symbol>,
 518         issue: u32,
 519     },
 520     /// The item does not have the `#[stable]` or `#[unstable]` marker assigned.
 521     Unmarked,
 522 }
 523
 524 impl<'gcx, 'tcx> TyCtxt<'gcx, 'tcx> {
 525     // See issue #38412.
 526     fn skip_stability_check_due_to_privacy(self, mut def_id: DefId) -> bool {
 527         // Check if `def_id` is a trait method.
 528         match self.def_kind(def_id) {
 529             Some(DefKind::Method) |
 530             Some(DefKind::AssocTy) |
 531             Some(DefKind::AssocConst) => {
 532                 if let ty::TraitContainer(trait_def_id) = self.associated_item(def_id).container {
 533                     // Trait methods do not declare visibility (even
 534                     // for visibility info in cstore). Use containing
 535                     // trait instead, so methods of `pub` traits are
 536                     // themselves considered `pub`.
 537                     def_id = trait_def_id;
 538                 }
 539             }
 540             _ => {}
 541         }
 542
 543         let visibility = self.visibility(def_id);
 544
 545         match visibility {
 546             // Must check stability for `pub` items.
 547             ty::Visibility::Public => false,
 548
 549             // These are not visible outside crate; therefore
 550             // stability markers are irrelevant, if even present.
 551             ty::Visibility::Restricted(..) |
 552             ty::Visibility::Invisible => true,
 553         }
 554     }
 555
 556     /// Evaluates the stability of an item.
 557     ///
 558     /// Returns `EvalResult::Allow` if the item is stable, or unstable but the corresponding
 559     /// `#![feature]` has been provided. Returns `EvalResult::Deny` which describes the offending
 560     /// unstable feature otherwise.
 561     ///
 562     /// If `id` is `Some(_)`, this function will also check if the item at `def_id` has been
 563     /// deprecated. If the item is indeed deprecated, we will emit a deprecation lint attached to
 564     /// `id`.
 565     pub fn eval_stability(self, def_id: DefId, id: Option<HirId>, span: Span) -> EvalResult {
 566         let lint_deprecated = |def_id: DefId,
 567                                id: HirId,
 568                                note: Option<Symbol>,
 569                                suggestion: Option<Symbol>,
 570                                message: &str,
 571                                lint: &'static Lint| {
 572             if in_derive_expansion(span) {
 573                 return;
 574             }
 575             let msg = if let Some(note) = note {
 576                 format!("{}: {}", message, note)
 577             } else {
 578                 format!("{}", message)
 579             };
 580
 581             let mut diag = self.struct_span_lint_hir(lint, id, span, &msg);
 582             if let Some(suggestion) = suggestion {
 583                 if let hir::Node::Expr(_) = self.hir().get_by_hir_id(id) {
 584                     diag.span_suggestion(
 585                         span,
 586                         "replace the use of the deprecated item",
 587                         suggestion.to_string(),
 588                         Applicability::MachineApplicable,
 589                     );
 590                 }
 591             }
 592             diag.emit();
 593             if id == hir::DUMMY_HIR_ID {
 594                 span_bug!(span, "emitted a {} lint with dummy HIR id: {:?}", lint.name, def_id);
 595             }
 596         };
 597
 598         // Deprecated attributes apply in-crate and cross-crate.
 599         if let Some(id) = id {
 600             if let Some(depr_entry) = self.lookup_deprecation_entry(def_id) {
 601                 let parent_def_id = self.hir().local_def_id_from_hir_id(
 602                     self.hir().get_parent_item(id));
 603                 let skip = self.lookup_deprecation_entry(parent_def_id)
 604                                .map_or(false, |parent_depr| parent_depr.same_origin(&depr_entry));
 605
 606                 if !skip {
 607                     let path = self.def_path_str(def_id);
 608                     let message = format!("use of deprecated item '{}'", path);
 609                     lint_deprecated(def_id,
 610                                     id,
 611                                     depr_entry.attr.note,
 612                                     None,
 613                                     &message,
 614                                     lint::builtin::DEPRECATED);
 615                 }
 616             };
 617         }
 618
 619         let is_staged_api = self.lookup_stability(DefId {
 620             index: CRATE_DEF_INDEX,
 621             ..def_id
 622         }).is_some();
 623         if !is_staged_api {
 624             return EvalResult::Allow;
 625         }
 626
 627         let stability = self.lookup_stability(def_id);
 628         debug!("stability: \
 629                 inspecting def_id={:?} span={:?} of stability={:?}", def_id, span, stability);
 630
 631         if let Some(id) = id {
 632             if let Some(stability) = stability {
 633                 if let Some(depr) = &stability.rustc_depr {
 634                     let path = self.def_path_str(def_id);
 635                     if deprecation_in_effect(&depr.since.as_str()) {
 636                         let message = format!("use of deprecated item '{}'", path);
 637                         lint_deprecated(def_id,
 638                                         id,
 639                                         Some(depr.reason),
 640                                         depr.suggestion,
 641                                         &message,
 642                                         lint::builtin::DEPRECATED);
 643                     } else {
 644                         let message = format!("use of item '{}' \
 645                                                 that will be deprecated in future version {}",
 646                                                 path,
 647                                                 depr.since);
 648                         lint_deprecated(def_id,
 649                                         id,
 650                                         Some(depr.reason),
 651                                         depr.suggestion,
 652                                         &message,
 653                                         lint::builtin::DEPRECATED_IN_FUTURE);
 654                     }
 655                 }
 656             }
 657         }
 658
 659         // Only the cross-crate scenario matters when checking unstable APIs
 660         let cross_crate = !def_id.is_local();
 661         if !cross_crate {
 662             return EvalResult::Allow;
 663         }
 664
 665         // Issue #38412: private items lack stability markers.
 666         if self.skip_stability_check_due_to_privacy(def_id) {
 667             return EvalResult::Allow;
 668         }
 669
 670         match stability {
 671             Some(&Stability { level: attr::Unstable { reason, issue }, feature, .. }) => {
 672                 if span.allows_unstable(feature) {
 673                     debug!("stability: skipping span={:?} since it is internal", span);
 674                     return EvalResult::Allow;
 675                 }
 676                 if self.stability().active_features.contains(&feature) {
 677                     return EvalResult::Allow;
 678                 }
 679
 680                 // When we're compiling the compiler itself we may pull in
 681                 // crates from crates.io, but those crates may depend on other
 682                 // crates also pulled in from crates.io. We want to ideally be
 683                 // able to compile everything without requiring upstream
 684                 // modifications, so in the case that this looks like a
 685                 // `rustc_private` crate (e.g., a compiler crate) and we also have
 686                 // the `-Z force-unstable-if-unmarked` flag present (we're
 687                 // compiling a compiler crate), then let this missing feature
 688                 // annotation slide.
 689                 if feature == sym::rustc_private && issue == 27812 {
 690                     if self.sess.opts.debugging_opts.force_unstable_if_unmarked {
 691                         return EvalResult::Allow;
 692                     }
 693                 }
 694
 695                 EvalResult::Deny { feature, reason, issue }
 696             }
 697             Some(_) => {
 698                 // Stable APIs are always ok to call and deprecated APIs are
 699                 // handled by the lint emitting logic above.
 700                 EvalResult::Allow
 701             }
 702             None => {
 703                 EvalResult::Unmarked
 704             }
 705         }
 706     }
 707
 708     /// Checks if an item is stable or error out.
 709     ///
 710     /// If the item defined by `def_id` is unstable and the corresponding `#![feature]` does not
 711     /// exist, emits an error.
 712     ///
 713     /// Additionally, this function will also check if the item is deprecated. If so, and `id` is
 714     /// not `None`, a deprecated lint attached to `id` will be emitted.
 715     pub fn check_stability(self, def_id: DefId, id: Option<HirId>, span: Span) {
 716         match self.eval_stability(def_id, id, span) {
 717             EvalResult::Allow => {}
 718             EvalResult::Deny { feature, reason, issue } => {
 719                 let msg = match reason {
 720                     Some(r) => format!("use of unstable library feature '{}': {}", feature, r),
 721                     None => format!("use of unstable library feature '{}'", &feature)
 722                 };
 723
 724                 let msp: MultiSpan = span.into();
 725                 let cm = &self.sess.parse_sess.source_map();
 726                 let span_key = msp.primary_span().and_then(|sp: Span|
 727                     if !sp.is_dummy() {
 728                         let file = cm.lookup_char_pos(sp.lo()).file;
 729                         if file.name.is_macros() {
 730                             None
 731                         } else {
 732                             Some(span)
 733                         }
 734                     } else {
 735                         None
 736                     }
 737                 );
 738
 739                 let error_id = (DiagnosticMessageId::StabilityId(issue), span_key, msg.clone());
 740                 let fresh = self.sess.one_time_diagnostics.borrow_mut().insert(error_id);
 741                 if fresh {
 742                     emit_feature_err(&self.sess.parse_sess, feature, span,
 743                                      GateIssue::Library(Some(issue)), &msg);
 744                 }
 745             }
 746             EvalResult::Unmarked => {
 747                 // The API could be uncallable for other reasons, for example when a private module
 748                 // was referenced.
 749                 self.sess.delay_span_bug(span, &format!("encountered unmarked API: {:?}", def_id));
 750             }
 751         }
 752     }
 753 }
 754
 755 impl Visitor<'tcx> for Checker<'tcx> {
 756     /// Because stability levels are scoped lexically, we want to walk
 757     /// nested items in the context of the outer item, so enable
 758     /// deep-walking.
 759     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 760         NestedVisitorMap::OnlyBodies(&self.tcx.hir())
 761     }
 762
 763     fn visit_item(&mut self, item: &'tcx hir::Item) {
 764         match item.node {
 765             hir::ItemKind::ExternCrate(_) => {
 766                 // compiler-generated `extern crate` items have a dummy span.
 767                 if item.span.is_dummy() { return }
 768
 769                 let def_id = self.tcx.hir().local_def_id_from_hir_id(item.hir_id);
 770                 let cnum = match self.tcx.extern_mod_stmt_cnum(def_id) {
 771                     Some(cnum) => cnum,
 772                     None => return,
 773                 };
 774                 let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
 775                 self.tcx.check_stability(def_id, Some(item.hir_id), item.span);
 776             }
 777
 778             // For implementations of traits, check the stability of each item
 779             // individually as it's possible to have a stable trait with unstable
 780             // items.
 781             hir::ItemKind::Impl(.., Some(ref t), _, ref impl_item_refs) => {
 782                 if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
 783                     for impl_item_ref in impl_item_refs {
 784                         let impl_item = self.tcx.hir().impl_item(impl_item_ref.id);
 785                         let trait_item_def_id = self.tcx.associated_items(trait_did)
 786                             .find(|item| item.ident.name == impl_item.ident.name)
 787                             .map(|item| item.def_id);
 788                         if let Some(def_id) = trait_item_def_id {
 789                             // Pass `None` to skip deprecation warnings.
 790                             self.tcx.check_stability(def_id, None, impl_item.span);
 791                         }
 792                     }
 793                 }
 794             }
 795
 796             // There's no good place to insert stability check for non-Copy unions,
 797             // so semi-randomly perform it here in stability.rs
 798             hir::ItemKind::Union(..) if !self.tcx.features().untagged_unions => {
 799                 let def_id = self.tcx.hir().local_def_id_from_hir_id(item.hir_id);
 800                 let adt_def = self.tcx.adt_def(def_id);
 801                 let ty = self.tcx.type_of(def_id);
 802
 803                 if adt_def.has_dtor(self.tcx) {
 804                     emit_feature_err(&self.tcx.sess.parse_sess,
 805                                      sym::untagged_unions, item.span, GateIssue::Language,
 806                                      "unions with `Drop` implementations are unstable");
 807                 } else {
 808                     let param_env = self.tcx.param_env(def_id);
 809                     if !param_env.can_type_implement_copy(self.tcx, ty).is_ok() {
 810                         emit_feature_err(&self.tcx.sess.parse_sess,
 811                                          sym::untagged_unions, item.span, GateIssue::Language,
 812                                          "unions with non-`Copy` fields are unstable");
 813                     }
 814                 }
 815             }
 816
 817             _ => (/* pass */)
 818         }
 819         intravisit::walk_item(self, item);
 820     }
 821
 822     fn visit_path(&mut self, path: &'tcx hir::Path, id: hir::HirId) {
 823         if let Some(def_id) = path.res.opt_def_id() {
 824             self.tcx.check_stability(def_id, Some(id), path.span)
 825         }
 826         intravisit::walk_path(self, path)
 827     }
 828 }
 829
 830 impl<'gcx, 'tcx> TyCtxt<'gcx, 'tcx> {
 831     pub fn lookup_deprecation(self, id: DefId) -> Option<Deprecation> {
 832         self.lookup_deprecation_entry(id).map(|depr| depr.attr)
 833     }
 834 }
 835
 836 /// Given the list of enabled features that were not language features (i.e., that
 837 /// were expected to be library features), and the list of features used from
 838 /// libraries, identify activated features that don't exist and error about them.
 839 pub fn check_unused_or_stable_features<'tcx>(tcx: TyCtxt<'tcx, 'tcx>) {
 840     let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
 841
 842     if tcx.stability().staged_api[&LOCAL_CRATE] {
 843         let krate = tcx.hir().krate();
 844         let mut missing = MissingStabilityAnnotations {
 845             tcx,
 846             access_levels,
 847         };
 848         missing.check_missing_stability(hir::CRATE_HIR_ID, krate.span, "crate");
 849         intravisit::walk_crate(&mut missing, krate);
 850         krate.visit_all_item_likes(&mut missing.as_deep_visitor());
 851     }
 852
 853     let declared_lang_features = &tcx.features().declared_lang_features;
 854     let mut lang_features = FxHashSet::default();
 855     for &(feature, span, since) in declared_lang_features {
 856         if let Some(since) = since {
 857             // Warn if the user has enabled an already-stable lang feature.
 858             unnecessary_stable_feature_lint(tcx, span, feature, since);
 859         }
 860         if lang_features.contains(&feature) {
 861             // Warn if the user enables a lang feature multiple times.
 862             duplicate_feature_err(tcx.sess, span, feature);
 863         }
 864         lang_features.insert(feature);
 865     }
 866
 867     let declared_lib_features = &tcx.features().declared_lib_features;
 868     let mut remaining_lib_features = FxHashMap::default();
 869     for (feature, span) in declared_lib_features {
 870         if remaining_lib_features.contains_key(&feature) {
 871             // Warn if the user enables a lib feature multiple times.
 872             duplicate_feature_err(tcx.sess, *span, *feature);
 873         }
 874         remaining_lib_features.insert(feature, span.clone());
 875     }
 876     // `stdbuild` has special handling for `libc`, so we need to
 877     // recognise the feature when building std.
 878     // Likewise, libtest is handled specially, so `test` isn't
 879     // available as we'd like it to be.
 880     // FIXME: only remove `libc` when `stdbuild` is active.
 881     // FIXME: remove special casing for `test`.
 882     remaining_lib_features.remove(&Symbol::intern("libc"));
 883     remaining_lib_features.remove(&sym::test);
 884
 885     let check_features =
 886         |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {
 887             for &(feature, since) in defined_features {
 888                 if let Some(since) = since {
 889                     if let Some(span) = remaining_lib_features.get(&feature) {
 890                         // Warn if the user has enabled an already-stable lib feature.
 891                         unnecessary_stable_feature_lint(tcx, *span, feature, since);
 892                     }
 893                 }
 894                 remaining_lib_features.remove(&feature);
 895                 if remaining_lib_features.is_empty() {
 896                     break;
 897                 }
 898             }
 899         };
 900
 901     // We always collect the lib features declared in the current crate, even if there are
 902     // no unknown features, because the collection also does feature attribute validation.
 903     let local_defined_features = tcx.lib_features().to_vec();
 904     if !remaining_lib_features.is_empty() {
 905         check_features(&mut remaining_lib_features, &local_defined_features);
 906
 907         for &cnum in &*tcx.crates() {
 908             if remaining_lib_features.is_empty() {
 909                 break;
 910             }
 911             check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
 912         }
 913     }
 914
 915     for (feature, span) in remaining_lib_features {
 916         struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
 917     }
 918
 919     // FIXME(#44232): the `used_features` table no longer exists, so we
 920     // don't lint about unused features. We should reenable this one day!
 921 }
 922
 923 fn unnecessary_stable_feature_lint<'tcx>(
 924     tcx: TyCtxt<'tcx, 'tcx>,
 925     span: Span,
 926     feature: Symbol,
 927     since: Symbol
 928 ) {
 929     tcx.lint_hir(lint::builtin::STABLE_FEATURES,
 930         hir::CRATE_HIR_ID,
 931         span,
 932         &format!("the feature `{}` has been stable since {} and no longer requires \
 933                   an attribute to enable", feature, since));
 934 }
 935
 936 fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
 937     struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)
 938         .emit();
 939 }