compiler/rustc_passes/src/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 use rustc_ast::Attribute;
   5 use rustc_attr::{self as attr, ConstStability, Stability};
   6 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   7 use rustc_errors::struct_span_err;
   8 use rustc_hir as hir;
   9 use rustc_hir::def::{DefKind, Res};
  10 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, CRATE_DEF_INDEX, LOCAL_CRATE};
  11 use rustc_hir::hir_id::CRATE_HIR_ID;
  12 use rustc_hir::intravisit::{self, Visitor};
  13 use rustc_hir::{FieldDef, Generics, HirId, Item, TraitRef, Ty, TyKind, Variant};
  14 use rustc_middle::hir::nested_filter;
  15 use rustc_middle::middle::privacy::AccessLevels;
  16 use rustc_middle::middle::stability::{DeprecationEntry, Index};
  17 use rustc_middle::ty::{self, query::Providers, TyCtxt};
  18 use rustc_session::lint;
  19 use rustc_session::lint::builtin::{INEFFECTIVE_UNSTABLE_TRAIT_IMPL, USELESS_DEPRECATED};
  20 use rustc_session::parse::feature_err;
  21 use rustc_session::Session;
  22 use rustc_span::symbol::{sym, Symbol};
  23 use rustc_span::{Span, DUMMY_SP};
  24 use rustc_target::spec::abi::Abi;
  25
  26 use std::cmp::Ordering;
  27 use std::iter;
  28 use std::mem::replace;
  29 use std::num::NonZeroU32;
  30
  31 #[derive(PartialEq)]
  32 enum AnnotationKind {
  33     // Annotation is required if not inherited from unstable parents
  34     Required,
  35     // Annotation is useless, reject it
  36     Prohibited,
  37     // Deprecation annotation is useless, reject it. (Stability attribute is still required.)
  38     DeprecationProhibited,
  39     // Annotation itself is useless, but it can be propagated to children
  40     Container,
  41 }
  42
  43 /// Whether to inherit deprecation flags for nested items. In most cases, we do want to inherit
  44 /// deprecation, because nested items rarely have individual deprecation attributes, and so
  45 /// should be treated as deprecated if their parent is. However, default generic parameters
  46 /// have separate deprecation attributes from their parents, so we do not wish to inherit
  47 /// deprecation in this case. For example, inheriting deprecation for `T` in `Foo<T>`
  48 /// would cause a duplicate warning arising from both `Foo` and `T` being deprecated.
  49 #[derive(Clone)]
  50 enum InheritDeprecation {
  51     Yes,
  52     No,
  53 }
  54
  55 impl InheritDeprecation {
  56     fn yes(&self) -> bool {
  57         matches!(self, InheritDeprecation::Yes)
  58     }
  59 }
  60
  61 /// Whether to inherit const stability flags for nested items. In most cases, we do not want to
  62 /// inherit const stability: just because an enclosing `fn` is const-stable does not mean
  63 /// all `extern` imports declared in it should be const-stable! However, trait methods
  64 /// inherit const stability attributes from their parent and do not have their own.
  65 enum InheritConstStability {
  66     Yes,
  67     No,
  68 }
  69
  70 impl InheritConstStability {
  71     fn yes(&self) -> bool {
  72         matches!(self, InheritConstStability::Yes)
  73     }
  74 }
  75
  76 enum InheritStability {
  77     Yes,
  78     No,
  79 }
  80
  81 impl InheritStability {
  82     fn yes(&self) -> bool {
  83         matches!(self, InheritStability::Yes)
  84     }
  85 }
  86
  87 // A private tree-walker for producing an Index.
  88 struct Annotator<'a, 'tcx> {
  89     tcx: TyCtxt<'tcx>,
  90     index: &'a mut Index<'tcx>,
  91     parent_stab: Option<&'tcx Stability>,
  92     parent_const_stab: Option<&'tcx ConstStability>,
  93     parent_depr: Option<DeprecationEntry>,
  94     in_trait_impl: bool,
  95 }
  96
  97 impl<'a, 'tcx> Annotator<'a, 'tcx> {
  98     // Determine the stability for a node based on its attributes and inherited
  99     // stability. The stability is recorded in the index and used as the parent.
 100     // If the node is a function, `fn_sig` is its signature
 101     fn annotate<F>(
 102         &mut self,
 103         def_id: LocalDefId,
 104         item_sp: Span,
 105         fn_sig: Option<&'tcx hir::FnSig<'tcx>>,
 106         kind: AnnotationKind,
 107         inherit_deprecation: InheritDeprecation,
 108         inherit_const_stability: InheritConstStability,
 109         inherit_from_parent: InheritStability,
 110         visit_children: F,
 111     ) where
 112         F: FnOnce(&mut Self),
 113     {
 114         let attrs = self.tcx.get_attrs(def_id.to_def_id());
 115         debug!("annotate(id = {:?}, attrs = {:?})", def_id, attrs);
 116         let mut did_error = false;
 117         if !self.tcx.features().staged_api {
 118             did_error = self.forbid_staged_api_attrs(def_id, attrs, inherit_deprecation.clone());
 119         }
 120
 121         let depr = if did_error { None } else { attr::find_deprecation(&self.tcx.sess, attrs) };
 122         let mut is_deprecated = false;
 123         if let Some((depr, span)) = &depr {
 124             is_deprecated = true;
 125
 126             if kind == AnnotationKind::Prohibited || kind == AnnotationKind::DeprecationProhibited {
 127                 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
 128                 self.tcx.struct_span_lint_hir(USELESS_DEPRECATED, hir_id, *span, |lint| {
 129                     lint.build("this `#[deprecated]` annotation has no effect")
 130                         .span_suggestion_short(
 131                             *span,
 132                             "remove the unnecessary deprecation attribute",
 133                             String::new(),
 134                             rustc_errors::Applicability::MachineApplicable,
 135                         )
 136                         .emit()
 137                 });
 138             }
 139
 140             // `Deprecation` is just two pointers, no need to intern it
 141             let depr_entry = DeprecationEntry::local(depr.clone(), def_id);
 142             self.index.depr_map.insert(def_id, depr_entry);
 143         } else if let Some(parent_depr) = self.parent_depr.clone() {
 144             if inherit_deprecation.yes() {
 145                 is_deprecated = true;
 146                 info!("tagging child {:?} as deprecated from parent", def_id);
 147                 self.index.depr_map.insert(def_id, parent_depr);
 148             }
 149         }
 150
 151         if self.tcx.features().staged_api {
 152             if let Some(a) = attrs.iter().find(|a| a.has_name(sym::deprecated)) {
 153                 self.tcx
 154                     .sess
 155                     .struct_span_err(a.span, "`#[deprecated]` cannot be used in staged API")
 156                     .span_label(a.span, "use `#[rustc_deprecated]` instead")
 157                     .span_label(item_sp, "")
 158                     .emit();
 159             }
 160         } else {
 161             self.recurse_with_stability_attrs(
 162                 depr.map(|(d, _)| DeprecationEntry::local(d, def_id)),
 163                 None,
 164                 None,
 165                 visit_children,
 166             );
 167             return;
 168         }
 169
 170         let (stab, const_stab) = attr::find_stability(&self.tcx.sess, attrs, item_sp);
 171         let mut const_span = None;
 172
 173         let const_stab = const_stab.map(|(const_stab, const_span_node)| {
 174             let const_stab = self.tcx.intern_const_stability(const_stab);
 175             self.index.const_stab_map.insert(def_id, const_stab);
 176             const_span = Some(const_span_node);
 177             const_stab
 178         });
 179
 180         // If the current node is a function, has const stability attributes and if it doesn not have an intrinsic ABI,
 181         // check if the function/method is const or the parent impl block is const
 182         if let (Some(const_span), Some(fn_sig)) = (const_span, fn_sig) {
 183             if fn_sig.header.abi != Abi::RustIntrinsic
 184                 && fn_sig.header.abi != Abi::PlatformIntrinsic
 185                 && !fn_sig.header.is_const()
 186             {
 187                 if !self.in_trait_impl
 188                     || (self.in_trait_impl && !self.tcx.is_const_fn_raw(def_id.to_def_id()))
 189                 {
 190                     missing_const_err(&self.tcx.sess, fn_sig.span, const_span);
 191                 }
 192             }
 193         }
 194
 195         // `impl const Trait for Type` items forward their const stability to their
 196         // immediate children.
 197         if const_stab.is_none() {
 198             debug!("annotate: const_stab not found, parent = {:?}", self.parent_const_stab);
 199             if let Some(parent) = self.parent_const_stab {
 200                 if parent.level.is_unstable() {
 201                     self.index.const_stab_map.insert(def_id, parent);
 202                 }
 203             }
 204         }
 205
 206         if let Some((rustc_attr::Deprecation { is_since_rustc_version: true, .. }, span)) = &depr {
 207             if stab.is_none() {
 208                 struct_span_err!(
 209                     self.tcx.sess,
 210                     *span,
 211                     E0549,
 212                     "rustc_deprecated attribute must be paired with \
 213                     either stable or unstable attribute"
 214                 )
 215                 .emit();
 216             }
 217         }
 218
 219         let stab = stab.map(|(stab, span)| {
 220             // Error if prohibited, or can't inherit anything from a container.
 221             if kind == AnnotationKind::Prohibited
 222                 || (kind == AnnotationKind::Container && stab.level.is_stable() && is_deprecated)
 223             {
 224                 self.tcx.sess.struct_span_err(span,"this stability annotation is useless")
 225                     .span_label(span, "useless stability annotation")
 226                     .span_label(item_sp, "the stability attribute annotates this item")
 227                     .emit();
 228             }
 229
 230             debug!("annotate: found {:?}", stab);
 231             let stab = self.tcx.intern_stability(stab);
 232
 233             // Check if deprecated_since < stable_since. If it is,
 234             // this is *almost surely* an accident.
 235             if let (&Some(dep_since), &attr::Stable { since: stab_since }) =
 236                 (&depr.as_ref().and_then(|(d, _)| d.since), &stab.level)
 237             {
 238                 // Explicit version of iter::order::lt to handle parse errors properly
 239                 for (dep_v, stab_v) in
 240                     iter::zip(dep_since.as_str().split('.'), stab_since.as_str().split('.'))
 241                 {
 242                     match stab_v.parse::<u64>() {
 243                         Err(_) => {
 244                             self.tcx.sess.struct_span_err(span, "invalid stability version found")
 245                                 .span_label(span, "invalid stability version")
 246                                 .span_label(item_sp, "the stability attribute annotates this item")
 247                                 .emit();
 248                             break;
 249                         }
 250                         Ok(stab_vp) => match dep_v.parse::<u64>() {
 251                             Ok(dep_vp) => match dep_vp.cmp(&stab_vp) {
 252                                 Ordering::Less => {
 253                                     self.tcx.sess.struct_span_err(span, "an API can't be stabilized after it is deprecated")
 254                                         .span_label(span, "invalid version")
 255                                         .span_label(item_sp, "the stability attribute annotates this item")
 256                                         .emit();
 257                                     break;
 258                                 }
 259                                 Ordering::Equal => continue,
 260                                 Ordering::Greater => break,
 261                             },
 262                             Err(_) => {
 263                                 if dep_v != "TBD" {
 264                                     self.tcx.sess.struct_span_err(span, "invalid deprecation version found")
 265                                         .span_label(span, "invalid deprecation version")
 266                                         .span_label(item_sp, "the stability attribute annotates this item")
 267                                         .emit();
 268                                 }
 269                                 break;
 270                             }
 271                         },
 272                     }
 273                 }
 274             }
 275
 276             self.index.stab_map.insert(def_id, stab);
 277             stab
 278         });
 279
 280         if stab.is_none() {
 281             debug!("annotate: stab not found, parent = {:?}", self.parent_stab);
 282             if let Some(stab) = self.parent_stab {
 283                 if inherit_deprecation.yes() && stab.level.is_unstable()
 284                     || inherit_from_parent.yes()
 285                 {
 286                     self.index.stab_map.insert(def_id, stab);
 287                 }
 288             }
 289         }
 290
 291         self.recurse_with_stability_attrs(
 292             depr.map(|(d, _)| DeprecationEntry::local(d, def_id)),
 293             stab,
 294             if inherit_const_stability.yes() { const_stab } else { None },
 295             visit_children,
 296         );
 297     }
 298
 299     fn recurse_with_stability_attrs(
 300         &mut self,
 301         depr: Option<DeprecationEntry>,
 302         stab: Option<&'tcx Stability>,
 303         const_stab: Option<&'tcx ConstStability>,
 304         f: impl FnOnce(&mut Self),
 305     ) {
 306         // These will be `Some` if this item changes the corresponding stability attribute.
 307         let mut replaced_parent_depr = None;
 308         let mut replaced_parent_stab = None;
 309         let mut replaced_parent_const_stab = None;
 310
 311         if let Some(depr) = depr {
 312             replaced_parent_depr = Some(replace(&mut self.parent_depr, Some(depr)));
 313         }
 314         if let Some(stab) = stab {
 315             replaced_parent_stab = Some(replace(&mut self.parent_stab, Some(stab)));
 316         }
 317         if let Some(const_stab) = const_stab {
 318             replaced_parent_const_stab =
 319                 Some(replace(&mut self.parent_const_stab, Some(const_stab)));
 320         }
 321
 322         f(self);
 323
 324         if let Some(orig_parent_depr) = replaced_parent_depr {
 325             self.parent_depr = orig_parent_depr;
 326         }
 327         if let Some(orig_parent_stab) = replaced_parent_stab {
 328             self.parent_stab = orig_parent_stab;
 329         }
 330         if let Some(orig_parent_const_stab) = replaced_parent_const_stab {
 331             self.parent_const_stab = orig_parent_const_stab;
 332         }
 333     }
 334
 335     // returns true if an error occurred, used to suppress some spurious errors
 336     fn forbid_staged_api_attrs(
 337         &mut self,
 338         def_id: LocalDefId,
 339         attrs: &[Attribute],
 340         inherit_deprecation: InheritDeprecation,
 341     ) -> bool {
 342         // Emit errors for non-staged-api crates.
 343         let unstable_attrs = [
 344             sym::unstable,
 345             sym::stable,
 346             sym::rustc_deprecated,
 347             sym::rustc_const_unstable,
 348             sym::rustc_const_stable,
 349         ];
 350         let mut has_error = false;
 351         for attr in attrs {
 352             let name = attr.name_or_empty();
 353             if unstable_attrs.contains(&name) {
 354                 struct_span_err!(
 355                     self.tcx.sess,
 356                     attr.span,
 357                     E0734,
 358                     "stability attributes may not be used outside of the standard library",
 359                 )
 360                 .emit();
 361                 has_error = true;
 362             }
 363         }
 364
 365         // Propagate unstability.  This can happen even for non-staged-api crates in case
 366         // -Zforce-unstable-if-unmarked is set.
 367         if let Some(stab) = self.parent_stab {
 368             if inherit_deprecation.yes() && stab.level.is_unstable() {
 369                 self.index.stab_map.insert(def_id, stab);
 370             }
 371         }
 372
 373         has_error
 374     }
 375 }
 376
 377 impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
 378     /// Because stability levels are scoped lexically, we want to walk
 379     /// nested items in the context of the outer item, so enable
 380     /// deep-walking.
 381     type NestedFilter = nested_filter::All;
 382
 383     fn nested_visit_map(&mut self) -> Self::Map {
 384         self.tcx.hir()
 385     }
 386
 387     fn visit_item(&mut self, i: &'tcx Item<'tcx>) {
 388         let orig_in_trait_impl = self.in_trait_impl;
 389         let mut kind = AnnotationKind::Required;
 390         let mut const_stab_inherit = InheritConstStability::No;
 391         let mut fn_sig = None;
 392
 393         match i.kind {
 394             // Inherent impls and foreign modules serve only as containers for other items,
 395             // they don't have their own stability. They still can be annotated as unstable
 396             // and propagate this unstability to children, but this annotation is completely
 397             // optional. They inherit stability from their parents when unannotated.
 398             hir::ItemKind::Impl(hir::Impl { of_trait: None, .. })
 399             | hir::ItemKind::ForeignMod { .. } => {
 400                 self.in_trait_impl = false;
 401                 kind = AnnotationKind::Container;
 402             }
 403             hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => {
 404                 self.in_trait_impl = true;
 405                 kind = AnnotationKind::DeprecationProhibited;
 406                 const_stab_inherit = InheritConstStability::Yes;
 407             }
 408             hir::ItemKind::Struct(ref sd, _) => {
 409                 if let Some(ctor_hir_id) = sd.ctor_hir_id() {
 410                     self.annotate(
 411                         self.tcx.hir().local_def_id(ctor_hir_id),
 412                         i.span,
 413                         None,
 414                         AnnotationKind::Required,
 415                         InheritDeprecation::Yes,
 416                         InheritConstStability::No,
 417                         InheritStability::Yes,
 418                         |_| {},
 419                     )
 420                 }
 421             }
 422             hir::ItemKind::Fn(ref item_fn_sig, _, _) => {
 423                 fn_sig = Some(item_fn_sig);
 424             }
 425             _ => {}
 426         }
 427
 428         self.annotate(
 429             i.def_id,
 430             i.span,
 431             fn_sig,
 432             kind,
 433             InheritDeprecation::Yes,
 434             const_stab_inherit,
 435             InheritStability::No,
 436             |v| intravisit::walk_item(v, i),
 437         );
 438         self.in_trait_impl = orig_in_trait_impl;
 439     }
 440
 441     fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
 442         let fn_sig = match ti.kind {
 443             hir::TraitItemKind::Fn(ref fn_sig, _) => Some(fn_sig),
 444             _ => None,
 445         };
 446
 447         self.annotate(
 448             ti.def_id,
 449             ti.span,
 450             fn_sig,
 451             AnnotationKind::Required,
 452             InheritDeprecation::Yes,
 453             InheritConstStability::No,
 454             InheritStability::No,
 455             |v| {
 456                 intravisit::walk_trait_item(v, ti);
 457             },
 458         );
 459     }
 460
 461     fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
 462         let kind =
 463             if self.in_trait_impl { AnnotationKind::Prohibited } else { AnnotationKind::Required };
 464
 465         let fn_sig = match ii.kind {
 466             hir::ImplItemKind::Fn(ref fn_sig, _) => Some(fn_sig),
 467             _ => None,
 468         };
 469
 470         self.annotate(
 471             ii.def_id,
 472             ii.span,
 473             fn_sig,
 474             kind,
 475             InheritDeprecation::Yes,
 476             InheritConstStability::No,
 477             InheritStability::No,
 478             |v| {
 479                 intravisit::walk_impl_item(v, ii);
 480             },
 481         );
 482     }
 483
 484     fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) {
 485         self.annotate(
 486             self.tcx.hir().local_def_id(var.id),
 487             var.span,
 488             None,
 489             AnnotationKind::Required,
 490             InheritDeprecation::Yes,
 491             InheritConstStability::No,
 492             InheritStability::Yes,
 493             |v| {
 494                 if let Some(ctor_hir_id) = var.data.ctor_hir_id() {
 495                     v.annotate(
 496                         v.tcx.hir().local_def_id(ctor_hir_id),
 497                         var.span,
 498                         None,
 499                         AnnotationKind::Required,
 500                         InheritDeprecation::Yes,
 501                         InheritConstStability::No,
 502                         InheritStability::No,
 503                         |_| {},
 504                     );
 505                 }
 506
 507                 intravisit::walk_variant(v, var, g, item_id)
 508             },
 509         )
 510     }
 511
 512     fn visit_field_def(&mut self, s: &'tcx FieldDef<'tcx>) {
 513         self.annotate(
 514             self.tcx.hir().local_def_id(s.hir_id),
 515             s.span,
 516             None,
 517             AnnotationKind::Required,
 518             InheritDeprecation::Yes,
 519             InheritConstStability::No,
 520             InheritStability::Yes,
 521             |v| {
 522                 intravisit::walk_field_def(v, s);
 523             },
 524         );
 525     }
 526
 527     fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) {
 528         self.annotate(
 529             i.def_id,
 530             i.span,
 531             None,
 532             AnnotationKind::Required,
 533             InheritDeprecation::Yes,
 534             InheritConstStability::No,
 535             InheritStability::No,
 536             |v| {
 537                 intravisit::walk_foreign_item(v, i);
 538             },
 539         );
 540     }
 541
 542     fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
 543         let kind = match &p.kind {
 544             // Allow stability attributes on default generic arguments.
 545             hir::GenericParamKind::Type { default: Some(_), .. }
 546             | hir::GenericParamKind::Const { default: Some(_), .. } => AnnotationKind::Container,
 547             _ => AnnotationKind::Prohibited,
 548         };
 549
 550         self.annotate(
 551             self.tcx.hir().local_def_id(p.hir_id),
 552             p.span,
 553             None,
 554             kind,
 555             InheritDeprecation::No,
 556             InheritConstStability::No,
 557             InheritStability::No,
 558             |v| {
 559                 intravisit::walk_generic_param(v, p);
 560             },
 561         );
 562     }
 563 }
 564
 565 struct MissingStabilityAnnotations<'tcx> {
 566     tcx: TyCtxt<'tcx>,
 567     access_levels: &'tcx AccessLevels,
 568 }
 569
 570 impl<'tcx> MissingStabilityAnnotations<'tcx> {
 571     fn check_missing_stability(&self, def_id: LocalDefId, span: Span) {
 572         let stab = self.tcx.stability().local_stability(def_id);
 573         if !self.tcx.sess.opts.test && stab.is_none() && self.access_levels.is_reachable(def_id) {
 574             let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
 575             self.tcx.sess.span_err(span, &format!("{} has missing stability attribute", descr));
 576         }
 577     }
 578
 579     fn check_missing_const_stability(&self, def_id: LocalDefId, span: Span) {
 580         if !self.tcx.features().staged_api {
 581             return;
 582         }
 583
 584         let is_const = self.tcx.is_const_fn(def_id.to_def_id());
 585         let is_stable = self
 586             .tcx
 587             .lookup_stability(def_id)
 588             .map_or(false, |stability| stability.level.is_stable());
 589         let missing_const_stability_attribute = self.tcx.lookup_const_stability(def_id).is_none();
 590         let is_reachable = self.access_levels.is_reachable(def_id);
 591
 592         if is_const && is_stable && missing_const_stability_attribute && is_reachable {
 593             let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id());
 594             self.tcx.sess.span_err(span, &format!("{descr} has missing const stability attribute"));
 595         }
 596     }
 597 }
 598
 599 impl<'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'tcx> {
 600     type NestedFilter = nested_filter::OnlyBodies;
 601
 602     fn nested_visit_map(&mut self) -> Self::Map {
 603         self.tcx.hir()
 604     }
 605
 606     fn visit_item(&mut self, i: &'tcx Item<'tcx>) {
 607         // Inherent impls and foreign modules serve only as containers for other items,
 608         // they don't have their own stability. They still can be annotated as unstable
 609         // and propagate this unstability to children, but this annotation is completely
 610         // optional. They inherit stability from their parents when unannotated.
 611         if !matches!(
 612             i.kind,
 613             hir::ItemKind::Impl(hir::Impl { of_trait: None, .. })
 614                 | hir::ItemKind::ForeignMod { .. }
 615         ) {
 616             self.check_missing_stability(i.def_id, i.span);
 617         }
 618
 619         // Ensure stable `const fn` have a const stability attribute.
 620         self.check_missing_const_stability(i.def_id, i.span);
 621
 622         intravisit::walk_item(self, i)
 623     }
 624
 625     fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) {
 626         self.check_missing_stability(ti.def_id, ti.span);
 627         intravisit::walk_trait_item(self, ti);
 628     }
 629
 630     fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) {
 631         let impl_def_id = self.tcx.hir().get_parent_item(ii.hir_id());
 632         if self.tcx.impl_trait_ref(impl_def_id).is_none() {
 633             self.check_missing_stability(ii.def_id, ii.span);
 634             self.check_missing_const_stability(ii.def_id, ii.span);
 635         }
 636         intravisit::walk_impl_item(self, ii);
 637     }
 638
 639     fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) {
 640         self.check_missing_stability(self.tcx.hir().local_def_id(var.id), var.span);
 641         intravisit::walk_variant(self, var, g, item_id);
 642     }
 643
 644     fn visit_field_def(&mut self, s: &'tcx FieldDef<'tcx>) {
 645         self.check_missing_stability(self.tcx.hir().local_def_id(s.hir_id), s.span);
 646         intravisit::walk_field_def(self, s);
 647     }
 648
 649     fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) {
 650         self.check_missing_stability(i.def_id, i.span);
 651         intravisit::walk_foreign_item(self, i);
 652     }
 653     // Note that we don't need to `check_missing_stability` for default generic parameters,
 654     // as we assume that any default generic parameters without attributes are automatically
 655     // stable (assuming they have not inherited instability from their parent).
 656 }
 657
 658 fn stability_index<'tcx>(tcx: TyCtxt<'tcx>, (): ()) -> Index<'tcx> {
 659     let is_staged_api =
 660         tcx.sess.opts.debugging_opts.force_unstable_if_unmarked || tcx.features().staged_api;
 661     let mut staged_api = FxHashMap::default();
 662     staged_api.insert(LOCAL_CRATE, is_staged_api);
 663     let mut index = Index {
 664         staged_api,
 665         stab_map: Default::default(),
 666         const_stab_map: Default::default(),
 667         depr_map: Default::default(),
 668         active_features: Default::default(),
 669     };
 670
 671     let active_lib_features = &tcx.features().declared_lib_features;
 672     let active_lang_features = &tcx.features().declared_lang_features;
 673
 674     // Put the active features into a map for quick lookup.
 675     index.active_features = active_lib_features
 676         .iter()
 677         .map(|&(s, ..)| s)
 678         .chain(active_lang_features.iter().map(|&(s, ..)| s))
 679         .collect();
 680
 681     {
 682         let mut annotator = Annotator {
 683             tcx,
 684             index: &mut index,
 685             parent_stab: None,
 686             parent_const_stab: None,
 687             parent_depr: None,
 688             in_trait_impl: false,
 689         };
 690
 691         // If the `-Z force-unstable-if-unmarked` flag is passed then we provide
 692         // a parent stability annotation which indicates that this is private
 693         // with the `rustc_private` feature. This is intended for use when
 694         // compiling `librustc_*` crates themselves so we can leverage crates.io
 695         // while maintaining the invariant that all sysroot crates are unstable
 696         // by default and are unable to be used.
 697         if tcx.sess.opts.debugging_opts.force_unstable_if_unmarked {
 698             let reason = "this crate is being loaded from the sysroot, an \
 699                           unstable location; did you mean to load this crate \
 700                           from crates.io via `Cargo.toml` instead?";
 701             let stability = tcx.intern_stability(Stability {
 702                 level: attr::StabilityLevel::Unstable {
 703                     reason: Some(Symbol::intern(reason)),
 704                     issue: NonZeroU32::new(27812),
 705                     is_soft: false,
 706                 },
 707                 feature: sym::rustc_private,
 708             });
 709             annotator.parent_stab = Some(stability);
 710         }
 711
 712         annotator.annotate(
 713             CRATE_DEF_ID,
 714             tcx.hir().span(CRATE_HIR_ID),
 715             None,
 716             AnnotationKind::Required,
 717             InheritDeprecation::Yes,
 718             InheritConstStability::No,
 719             InheritStability::No,
 720             |v| tcx.hir().walk_toplevel_module(v),
 721         );
 722     }
 723     index
 724 }
 725
 726 /// Cross-references the feature names of unstable APIs with enabled
 727 /// features and possibly prints errors.
 728 fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
 729     tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx }.as_deep_visitor());
 730 }
 731
 732 pub(crate) fn provide(providers: &mut Providers) {
 733     *providers = Providers { check_mod_unstable_api_usage, stability_index, ..*providers };
 734 }
 735
 736 struct Checker<'tcx> {
 737     tcx: TyCtxt<'tcx>,
 738 }
 739
 740 impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
 741     type NestedFilter = nested_filter::OnlyBodies;
 742
 743     /// Because stability levels are scoped lexically, we want to walk
 744     /// nested items in the context of the outer item, so enable
 745     /// deep-walking.
 746     fn nested_visit_map(&mut self) -> Self::Map {
 747         self.tcx.hir()
 748     }
 749
 750     fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
 751         match item.kind {
 752             hir::ItemKind::ExternCrate(_) => {
 753                 // compiler-generated `extern crate` items have a dummy span.
 754                 // `std` is still checked for the `restricted-std` feature.
 755                 if item.span.is_dummy() && item.ident.as_str() != "std" {
 756                     return;
 757                 }
 758
 759                 let cnum = match self.tcx.extern_mod_stmt_cnum(item.def_id) {
 760                     Some(cnum) => cnum,
 761                     None => return,
 762                 };
 763                 let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX };
 764                 self.tcx.check_stability(def_id, Some(item.hir_id()), item.span, None);
 765             }
 766
 767             // For implementations of traits, check the stability of each item
 768             // individually as it's possible to have a stable trait with unstable
 769             // items.
 770             hir::ItemKind::Impl(hir::Impl { of_trait: Some(ref t), self_ty, items, .. }) => {
 771                 if self.tcx.features().staged_api {
 772                     // If this impl block has an #[unstable] attribute, give an
 773                     // error if all involved types and traits are stable, because
 774                     // it will have no effect.
 775                     // See: https://github.com/rust-lang/rust/issues/55436
 776                     let attrs = self.tcx.hir().attrs(item.hir_id());
 777                     if let (Some((Stability { level: attr::Unstable { .. }, .. }, span)), _) =
 778                         attr::find_stability(&self.tcx.sess, attrs, item.span)
 779                     {
 780                         let mut c = CheckTraitImplStable { tcx: self.tcx, fully_stable: true };
 781                         c.visit_ty(self_ty);
 782                         c.visit_trait_ref(t);
 783                         if c.fully_stable {
 784                             self.tcx.struct_span_lint_hir(
 785                                 INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
 786                                 item.hir_id(),
 787                                 span,
 788                                 |lint| lint
 789                                     .build("an `#[unstable]` annotation here has no effect")
 790                                     .note("see issue #55436 <https://github.com/rust-lang/rust/issues/55436> for more information")
 791                                     .emit()
 792                             );
 793                         }
 794                     }
 795                 }
 796
 797                 for impl_item_ref in items {
 798                     let impl_item = self.tcx.associated_item(impl_item_ref.id.def_id);
 799
 800                     if let Some(def_id) = impl_item.trait_item_def_id {
 801                         // Pass `None` to skip deprecation warnings.
 802                         self.tcx.check_stability(def_id, None, impl_item_ref.span, None);
 803                     }
 804                 }
 805             }
 806
 807             // There's no good place to insert stability check for non-Copy unions,
 808             // so semi-randomly perform it here in stability.rs
 809             hir::ItemKind::Union(..) if !self.tcx.features().untagged_unions => {
 810                 let ty = self.tcx.type_of(item.def_id);
 811                 let (adt_def, substs) = match ty.kind() {
 812                     ty::Adt(adt_def, substs) => (adt_def, substs),
 813                     _ => bug!(),
 814                 };
 815
 816                 // Non-`Copy` fields are unstable, except for `ManuallyDrop`.
 817                 let param_env = self.tcx.param_env(item.def_id);
 818                 for field in &adt_def.non_enum_variant().fields {
 819                     let field_ty = field.ty(self.tcx, substs);
 820                     if !field_ty.ty_adt_def().map_or(false, |adt_def| adt_def.is_manually_drop())
 821                         && !field_ty.is_copy_modulo_regions(self.tcx.at(DUMMY_SP), param_env)
 822                     {
 823                         if field_ty.needs_drop(self.tcx, param_env) {
 824                             // Avoid duplicate error: This will error later anyway because fields
 825                             // that need drop are not allowed.
 826                             self.tcx.sess.delay_span_bug(
 827                                 item.span,
 828                                 "union should have been rejected due to potentially dropping field",
 829                             );
 830                         } else {
 831                             feature_err(
 832                                 &self.tcx.sess.parse_sess,
 833                                 sym::untagged_unions,
 834                                 self.tcx.def_span(field.did),
 835                                 "unions with non-`Copy` fields other than `ManuallyDrop<T>` are unstable",
 836                             )
 837                             .emit();
 838                         }
 839                     }
 840                 }
 841             }
 842
 843             _ => (/* pass */),
 844         }
 845         intravisit::walk_item(self, item);
 846     }
 847
 848     fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) {
 849         if let Some(def_id) = path.res.opt_def_id() {
 850             let method_span = path.segments.last().map(|s| s.ident.span);
 851             self.tcx.check_stability(def_id, Some(id), path.span, method_span)
 852         }
 853         intravisit::walk_path(self, path)
 854     }
 855 }
 856
 857 struct CheckTraitImplStable<'tcx> {
 858     tcx: TyCtxt<'tcx>,
 859     fully_stable: bool,
 860 }
 861
 862 impl<'tcx> Visitor<'tcx> for CheckTraitImplStable<'tcx> {
 863     fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _id: hir::HirId) {
 864         if let Some(def_id) = path.res.opt_def_id() {
 865             if let Some(stab) = self.tcx.lookup_stability(def_id) {
 866                 self.fully_stable &= stab.level.is_stable();
 867             }
 868         }
 869         intravisit::walk_path(self, path)
 870     }
 871
 872     fn visit_trait_ref(&mut self, t: &'tcx TraitRef<'tcx>) {
 873         if let Res::Def(DefKind::Trait, trait_did) = t.path.res {
 874             if let Some(stab) = self.tcx.lookup_stability(trait_did) {
 875                 self.fully_stable &= stab.level.is_stable();
 876             }
 877         }
 878         intravisit::walk_trait_ref(self, t)
 879     }
 880
 881     fn visit_ty(&mut self, t: &'tcx Ty<'tcx>) {
 882         if let TyKind::Never = t.kind {
 883             self.fully_stable = false;
 884         }
 885         intravisit::walk_ty(self, t)
 886     }
 887 }
 888
 889 /// Given the list of enabled features that were not language features (i.e., that
 890 /// were expected to be library features), and the list of features used from
 891 /// libraries, identify activated features that don't exist and error about them.
 892 pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) {
 893     let access_levels = &tcx.privacy_access_levels(());
 894
 895     if tcx.stability().staged_api[&LOCAL_CRATE] {
 896         let mut missing = MissingStabilityAnnotations { tcx, access_levels };
 897         missing.check_missing_stability(CRATE_DEF_ID, tcx.hir().span(CRATE_HIR_ID));
 898         tcx.hir().walk_toplevel_module(&mut missing);
 899         tcx.hir().visit_all_item_likes(&mut missing.as_deep_visitor());
 900     }
 901
 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);
 908         }
 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);
 912         }
 913     }
 914
 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 !tcx.sess.opts.unstable_features.is_nightly_build() {
 919             struct_span_err!(
 920                 tcx.sess,
 921                 *span,
 922                 E0554,
 923                 "`#![feature]` may not be used on the {} release channel",
 924                 env!("CFG_RELEASE_CHANNEL")
 925             )
 926             .emit();
 927         }
 928         if remaining_lib_features.contains_key(&feature) {
 929             // Warn if the user enables a lib feature multiple times.
 930             duplicate_feature_err(tcx.sess, *span, *feature);
 931         }
 932         remaining_lib_features.insert(feature, *span);
 933     }
 934     // `stdbuild` has special handling for `libc`, so we need to
 935     // recognise the feature when building std.
 936     // Likewise, libtest is handled specially, so `test` isn't
 937     // available as we'd like it to be.
 938     // FIXME: only remove `libc` when `stdbuild` is active.
 939     // FIXME: remove special casing for `test`.
 940     remaining_lib_features.remove(&sym::libc);
 941     remaining_lib_features.remove(&sym::test);
 942
 943     let check_features = |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {
 944         for &(feature, since) in defined_features {
 945             if let Some(since) = since {
 946                 if let Some(span) = remaining_lib_features.get(&feature) {
 947                     // Warn if the user has enabled an already-stable lib feature.
 948                     unnecessary_stable_feature_lint(tcx, *span, feature, since);
 949                 }
 950             }
 951             remaining_lib_features.remove(&feature);
 952             if remaining_lib_features.is_empty() {
 953                 break;
 954             }
 955         }
 956     };
 957
 958     // We always collect the lib features declared in the current crate, even if there are
 959     // no unknown features, because the collection also does feature attribute validation.
 960     let local_defined_features = tcx.lib_features(()).to_vec();
 961     if !remaining_lib_features.is_empty() {
 962         check_features(&mut remaining_lib_features, &local_defined_features);
 963
 964         for &cnum in tcx.crates(()) {
 965             if remaining_lib_features.is_empty() {
 966                 break;
 967             }
 968             check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
 969         }
 970     }
 971
 972     for (feature, span) in remaining_lib_features {
 973         struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit();
 974     }
 975
 976     // FIXME(#44232): the `used_features` table no longer exists, so we
 977     // don't lint about unused features. We should re-enable this one day!
 978 }
 979
 980 fn unnecessary_stable_feature_lint(tcx: TyCtxt<'_>, span: Span, feature: Symbol, since: Symbol) {
 981     tcx.struct_span_lint_hir(lint::builtin::STABLE_FEATURES, hir::CRATE_HIR_ID, span, |lint| {
 982         lint.build(&format!(
 983             "the feature `{}` has been stable since {} and no longer requires \
 984                       an attribute to enable",
 985             feature, since
 986         ))
 987         .emit();
 988     });
 989 }
 990
 991 fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) {
 992     struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature)
 993         .emit();
 994 }
 995
 996 fn missing_const_err(session: &Session, fn_sig_span: Span, const_span: Span) {
 997     const ERROR_MSG: &'static str = "attributes `#[rustc_const_unstable]` \
 998          and `#[rustc_const_stable]` require \
 999          the function or method to be `const`";
1000
1001     session
1002         .struct_span_err(fn_sig_span, ERROR_MSG)
1003         .span_help(fn_sig_span, "make the function or method const")
1004         .span_label(const_span, "attribute specified here")
1005         .emit();
1006 }