compiler/rustc_lint/src/levels.rs

   1 use crate::context::{CheckLintNameResult, LintStore};
   2 use crate::late::unerased_lint_store;
   3 use rustc_ast as ast;
   4 use rustc_ast_pretty::pprust;
   5 use rustc_data_structures::fx::FxHashMap;
   6 use rustc_errors::{struct_span_err, Applicability, Diagnostic, MultiSpan};
   7 use rustc_hir as hir;
   8 use rustc_hir::{intravisit, HirId};
   9 use rustc_middle::hir::nested_filter;
  10 use rustc_middle::lint::{
  11     struct_lint_level, LevelAndSource, LintDiagnosticBuilder, LintExpectation, LintLevelMap,
  12     LintLevelSets, LintLevelSource, LintSet, LintStackIndex, COMMAND_LINE,
  13 };
  14 use rustc_middle::ty::query::Providers;
  15 use rustc_middle::ty::{RegisteredTools, TyCtxt};
  16 use rustc_session::lint::{
  17     builtin::{self, FORBIDDEN_LINT_GROUPS, SINGLE_USE_LIFETIMES, UNFULFILLED_LINT_EXPECTATIONS},
  18     Level, Lint, LintExpectationId, LintId,
  19 };
  20 use rustc_session::parse::{add_feature_diagnostics, feature_err};
  21 use rustc_session::Session;
  22 use rustc_span::symbol::{sym, Symbol};
  23 use rustc_span::{Span, DUMMY_SP};
  24 use tracing::debug;
  25
  26 fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
  27     let store = unerased_lint_store(tcx);
  28     let levels =
  29         LintLevelsBuilder::new(tcx.sess, false, &store, &tcx.resolutions(()).registered_tools);
  30     let mut builder = LintLevelMapBuilder { levels, tcx };
  31     let krate = tcx.hir().krate();
  32
  33     builder.levels.id_to_set.reserve(krate.owners.len() + 1);
  34
  35     let push =
  36         builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), true, Some(hir::CRATE_HIR_ID));
  37
  38     builder.levels.register_id(hir::CRATE_HIR_ID);
  39     tcx.hir().walk_toplevel_module(&mut builder);
  40     builder.levels.pop(push);
  41
  42     builder.levels.update_unstable_expectation_ids();
  43     builder.levels.build_map()
  44 }
  45
  46 pub struct LintLevelsBuilder<'s> {
  47     sess: &'s Session,
  48     lint_expectations: Vec<(LintExpectationId, LintExpectation)>,
  49     /// Each expectation has a stable and an unstable identifier. This map
  50     /// is used to map from unstable to stable [`LintExpectationId`]s.
  51     expectation_id_map: FxHashMap<LintExpectationId, LintExpectationId>,
  52     sets: LintLevelSets,
  53     id_to_set: FxHashMap<HirId, LintStackIndex>,
  54     cur: LintStackIndex,
  55     warn_about_weird_lints: bool,
  56     store: &'s LintStore,
  57     registered_tools: &'s RegisteredTools,
  58 }
  59
  60 pub struct BuilderPush {
  61     prev: LintStackIndex,
  62     pub changed: bool,
  63 }
  64
  65 impl<'s> LintLevelsBuilder<'s> {
  66     pub fn new(
  67         sess: &'s Session,
  68         warn_about_weird_lints: bool,
  69         store: &'s LintStore,
  70         registered_tools: &'s RegisteredTools,
  71     ) -> Self {
  72         let mut builder = LintLevelsBuilder {
  73             sess,
  74             lint_expectations: Default::default(),
  75             expectation_id_map: Default::default(),
  76             sets: LintLevelSets::new(),
  77             cur: COMMAND_LINE,
  78             id_to_set: Default::default(),
  79             warn_about_weird_lints,
  80             store,
  81             registered_tools,
  82         };
  83         builder.process_command_line(sess, store);
  84         assert_eq!(builder.sets.list.len(), 1);
  85         builder
  86     }
  87
  88     pub(crate) fn sess(&self) -> &Session {
  89         self.sess
  90     }
  91
  92     pub(crate) fn lint_store(&self) -> &LintStore {
  93         self.store
  94     }
  95
  96     fn current_specs(&self) -> &FxHashMap<LintId, LevelAndSource> {
  97         &self.sets.list[self.cur].specs
  98     }
  99
 100     fn current_specs_mut(&mut self) -> &mut FxHashMap<LintId, LevelAndSource> {
 101         &mut self.sets.list[self.cur].specs
 102     }
 103
 104     fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
 105         self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
 106
 107         self.cur =
 108             self.sets.list.push(LintSet { specs: FxHashMap::default(), parent: COMMAND_LINE });
 109         for &(ref lint_name, level) in &sess.opts.lint_opts {
 110             store.check_lint_name_cmdline(sess, &lint_name, level, self.registered_tools);
 111             let orig_level = level;
 112             let lint_flag_val = Symbol::intern(lint_name);
 113
 114             let Ok(ids) = store.find_lints(&lint_name) else {
 115                 // errors handled in check_lint_name_cmdline above
 116                 continue
 117             };
 118             for id in ids {
 119                 // ForceWarn and Forbid cannot be overridden
 120                 if let Some((Level::ForceWarn(_) | Level::Forbid, _)) =
 121                     self.current_specs().get(&id)
 122                 {
 123                     continue;
 124                 }
 125
 126                 if self.check_gated_lint(id, DUMMY_SP) {
 127                     let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
 128                     self.current_specs_mut().insert(id, (level, src));
 129                 }
 130             }
 131         }
 132     }
 133
 134     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
 135     /// (e.g. if a forbid was already inserted on the same scope), then emits a
 136     /// diagnostic with no change to `specs`.
 137     fn insert_spec(&mut self, id: LintId, (level, src): LevelAndSource) {
 138         let (old_level, old_src) =
 139             self.sets.get_lint_level(id.lint, self.cur, Some(self.current_specs()), &self.sess);
 140         // Setting to a non-forbid level is an error if the lint previously had
 141         // a forbid level. Note that this is not necessarily true even with a
 142         // `#[forbid(..)]` attribute present, as that is overridden by `--cap-lints`.
 143         //
 144         // This means that this only errors if we're truly lowering the lint
 145         // level from forbid.
 146         if level != Level::Forbid {
 147             if let Level::Forbid = old_level {
 148                 // Backwards compatibility check:
 149                 //
 150                 // We used to not consider `forbid(lint_group)`
 151                 // as preventing `allow(lint)` for some lint `lint` in
 152                 // `lint_group`. For now, issue a future-compatibility
 153                 // warning for this case.
 154                 let id_name = id.lint.name_lower();
 155                 let fcw_warning = match old_src {
 156                     LintLevelSource::Default => false,
 157                     LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
 158                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
 159                 };
 160                 debug!(
 161                     "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
 162                     fcw_warning,
 163                     self.current_specs(),
 164                     old_src,
 165                     id_name
 166                 );
 167
 168                 let decorate_diag = |diag: &mut Diagnostic| {
 169                     diag.span_label(src.span(), "overruled by previous forbid");
 170                     match old_src {
 171                         LintLevelSource::Default => {
 172                             diag.note(&format!(
 173                                 "`forbid` lint level is the default for {}",
 174                                 id.to_string()
 175                             ));
 176                         }
 177                         LintLevelSource::Node(_, forbid_source_span, reason) => {
 178                             diag.span_label(forbid_source_span, "`forbid` level set here");
 179                             if let Some(rationale) = reason {
 180                                 diag.note(rationale.as_str());
 181                             }
 182                         }
 183                         LintLevelSource::CommandLine(_, _) => {
 184                             diag.note("`forbid` lint level was set on command line");
 185                         }
 186                     }
 187                 };
 188                 if !fcw_warning {
 189                     let mut diag_builder = struct_span_err!(
 190                         self.sess,
 191                         src.span(),
 192                         E0453,
 193                         "{}({}) incompatible with previous forbid",
 194                         level.as_str(),
 195                         src.name(),
 196                     );
 197                     decorate_diag(&mut diag_builder);
 198                     diag_builder.emit();
 199                 } else {
 200                     self.struct_lint(
 201                         FORBIDDEN_LINT_GROUPS,
 202                         Some(src.span().into()),
 203                         |diag_builder| {
 204                             let mut diag_builder = diag_builder.build(&format!(
 205                                 "{}({}) incompatible with previous forbid",
 206                                 level.as_str(),
 207                                 src.name(),
 208                             ));
 209                             decorate_diag(&mut diag_builder);
 210                             diag_builder.emit();
 211                         },
 212                     );
 213                 }
 214
 215                 // Retain the forbid lint level, unless we are
 216                 // issuing a FCW. In the FCW case, we want to
 217                 // respect the new setting.
 218                 if !fcw_warning {
 219                     return;
 220                 }
 221             }
 222         }
 223
 224         // The lint `unfulfilled_lint_expectations` can't be expected, as it would suppress itself.
 225         // Handling expectations of this lint would add additional complexity with little to no
 226         // benefit. The expect level for this lint will therefore be ignored.
 227         if let Level::Expect(_) = level && id == LintId::of(UNFULFILLED_LINT_EXPECTATIONS) {
 228             return;
 229         }
 230
 231         match (old_level, level) {
 232             // If the new level is an expectation store it in `ForceWarn`
 233             (Level::ForceWarn(_), Level::Expect(expectation_id)) => self
 234                 .current_specs_mut()
 235                 .insert(id, (Level::ForceWarn(Some(expectation_id)), old_src)),
 236             // Keep `ForceWarn` level but drop the expectation
 237             (Level::ForceWarn(_), _) => {
 238                 self.current_specs_mut().insert(id, (Level::ForceWarn(None), old_src))
 239             }
 240             // Set the lint level as normal
 241             _ => self.current_specs_mut().insert(id, (level, src)),
 242         };
 243     }
 244
 245     /// Pushes a list of AST lint attributes onto this context.
 246     ///
 247     /// This function will return a `BuilderPush` object which should be passed
 248     /// to `pop` when this scope for the attributes provided is exited.
 249     ///
 250     /// This function will perform a number of tasks:
 251     ///
 252     /// * It'll validate all lint-related attributes in `attrs`
 253     /// * It'll mark all lint-related attributes as used
 254     /// * Lint levels will be updated based on the attributes provided
 255     /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
 256     ///   `#[allow]`
 257     ///
 258     /// Don't forget to call `pop`!
 259     pub(crate) fn push(
 260         &mut self,
 261         attrs: &[ast::Attribute],
 262         is_crate_node: bool,
 263         source_hir_id: Option<HirId>,
 264     ) -> BuilderPush {
 265         let prev = self.cur;
 266         self.cur = self.sets.list.push(LintSet { specs: FxHashMap::default(), parent: prev });
 267
 268         let sess = self.sess;
 269         let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
 270         for (attr_index, attr) in attrs.iter().enumerate() {
 271             if attr.has_name(sym::automatically_derived) {
 272                 self.current_specs_mut().insert(
 273                     LintId::of(SINGLE_USE_LIFETIMES),
 274                     (Level::Allow, LintLevelSource::Default),
 275                 );
 276                 continue;
 277             }
 278
 279             let level = match Level::from_attr(attr) {
 280                 None => continue,
 281                 // This is the only lint level with a `LintExpectationId` that can be created from an attribute
 282                 Some(Level::Expect(unstable_id)) if let Some(hir_id) = source_hir_id => {
 283                     let stable_id = self.create_stable_id(unstable_id, hir_id, attr_index);
 284
 285                     Level::Expect(stable_id)
 286                 }
 287                 Some(lvl) => lvl,
 288             };
 289
 290             let Some(mut metas) = attr.meta_item_list() else {
 291                 continue
 292             };
 293
 294             if metas.is_empty() {
 295                 // This emits the unused_attributes lint for `#[level()]`
 296                 continue;
 297             }
 298
 299             // Before processing the lint names, look for a reason (RFC 2383)
 300             // at the end.
 301             let mut reason = None;
 302             let tail_li = &metas[metas.len() - 1];
 303             if let Some(item) = tail_li.meta_item() {
 304                 match item.kind {
 305                     ast::MetaItemKind::Word => {} // actual lint names handled later
 306                     ast::MetaItemKind::NameValue(ref name_value) => {
 307                         if item.path == sym::reason {
 308                             if let ast::LitKind::Str(rationale, _) = name_value.kind {
 309                                 if !self.sess.features_untracked().lint_reasons {
 310                                     feature_err(
 311                                         &self.sess.parse_sess,
 312                                         sym::lint_reasons,
 313                                         item.span,
 314                                         "lint reasons are experimental",
 315                                     )
 316                                     .emit();
 317                                 }
 318                                 reason = Some(rationale);
 319                             } else {
 320                                 bad_attr(name_value.span)
 321                                     .span_label(name_value.span, "reason must be a string literal")
 322                                     .emit();
 323                             }
 324                             // found reason, reslice meta list to exclude it
 325                             metas.pop().unwrap();
 326                         } else {
 327                             bad_attr(item.span)
 328                                 .span_label(item.span, "bad attribute argument")
 329                                 .emit();
 330                         }
 331                     }
 332                     ast::MetaItemKind::List(_) => {
 333                         bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
 334                     }
 335                 }
 336             }
 337
 338             for (lint_index, li) in metas.iter_mut().enumerate() {
 339                 let level = match level {
 340                     Level::Expect(mut id) => {
 341                         id.set_lint_index(Some(lint_index as u16));
 342                         Level::Expect(id)
 343                     }
 344                     level => level,
 345                 };
 346
 347                 let sp = li.span();
 348                 let meta_item = match li {
 349                     ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
 350                     _ => {
 351                         let mut err = bad_attr(sp);
 352                         let mut add_label = true;
 353                         if let Some(item) = li.meta_item() {
 354                             if let ast::MetaItemKind::NameValue(_) = item.kind {
 355                                 if item.path == sym::reason {
 356                                     err.span_label(sp, "reason in lint attribute must come last");
 357                                     add_label = false;
 358                                 }
 359                             }
 360                         }
 361                         if add_label {
 362                             err.span_label(sp, "bad attribute argument");
 363                         }
 364                         err.emit();
 365                         continue;
 366                     }
 367                 };
 368                 let tool_ident = if meta_item.path.segments.len() > 1 {
 369                     Some(meta_item.path.segments.remove(0).ident)
 370                 } else {
 371                     None
 372                 };
 373                 let tool_name = tool_ident.map(|ident| ident.name);
 374                 let name = pprust::path_to_string(&meta_item.path);
 375                 let lint_result =
 376                     self.store.check_lint_name(&name, tool_name, self.registered_tools);
 377                 match &lint_result {
 378                     CheckLintNameResult::Ok(ids) => {
 379                         // This checks for instances where the user writes `#[expect(unfulfilled_lint_expectations)]`
 380                         // in that case we want to avoid overriding the lint level but instead add an expectation that
 381                         // can't be fulfilled. The lint message will include an explanation, that the
 382                         // `unfulfilled_lint_expectations` lint can't be expected.
 383                         if let Level::Expect(expect_id) = level {
 384                             // The `unfulfilled_lint_expectations` lint is not part of any lint groups. Therefore. we
 385                             // only need to check the slice if it contains a single lint.
 386                             let is_unfulfilled_lint_expectations = match ids {
 387                                 [lint] => *lint == LintId::of(UNFULFILLED_LINT_EXPECTATIONS),
 388                                 _ => false,
 389                             };
 390                             self.lint_expectations.push((
 391                                 expect_id,
 392                                 LintExpectation::new(
 393                                     reason,
 394                                     sp,
 395                                     is_unfulfilled_lint_expectations,
 396                                     tool_name,
 397                                 ),
 398                             ));
 399                         }
 400                         let src = LintLevelSource::Node(
 401                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 402                             sp,
 403                             reason,
 404                         );
 405                         for &id in *ids {
 406                             if self.check_gated_lint(id, attr.span) {
 407                                 self.insert_spec(id, (level, src));
 408                             }
 409                         }
 410                     }
 411
 412                     CheckLintNameResult::Tool(result) => {
 413                         match *result {
 414                             Ok(ids) => {
 415                                 let complete_name =
 416                                     &format!("{}::{}", tool_ident.unwrap().name, name);
 417                                 let src = LintLevelSource::Node(
 418                                     Symbol::intern(complete_name),
 419                                     sp,
 420                                     reason,
 421                                 );
 422                                 for id in ids {
 423                                     self.insert_spec(*id, (level, src));
 424                                 }
 425                                 if let Level::Expect(expect_id) = level {
 426                                     self.lint_expectations.push((
 427                                         expect_id,
 428                                         LintExpectation::new(reason, sp, false, tool_name),
 429                                     ));
 430                                 }
 431                             }
 432                             Err((Some(ids), ref new_lint_name)) => {
 433                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 434                                 let (lvl, src) = self.sets.get_lint_level(
 435                                     lint,
 436                                     self.cur,
 437                                     Some(self.current_specs()),
 438                                     &sess,
 439                                 );
 440                                 struct_lint_level(
 441                                     self.sess,
 442                                     lint,
 443                                     lvl,
 444                                     src,
 445                                     Some(sp.into()),
 446                                     |lint| {
 447                                         let msg = format!(
 448                                             "lint name `{}` is deprecated \
 449                                              and may not have an effect in the future.",
 450                                             name
 451                                         );
 452                                         lint.build(&msg)
 453                                             .span_suggestion(
 454                                                 sp,
 455                                                 "change it to",
 456                                                 new_lint_name,
 457                                                 Applicability::MachineApplicable,
 458                                             )
 459                                             .emit();
 460                                     },
 461                                 );
 462
 463                                 let src = LintLevelSource::Node(
 464                                     Symbol::intern(&new_lint_name),
 465                                     sp,
 466                                     reason,
 467                                 );
 468                                 for id in ids {
 469                                     self.insert_spec(*id, (level, src));
 470                                 }
 471                                 if let Level::Expect(expect_id) = level {
 472                                     self.lint_expectations.push((
 473                                         expect_id,
 474                                         LintExpectation::new(reason, sp, false, tool_name),
 475                                     ));
 476                                 }
 477                             }
 478                             Err((None, _)) => {
 479                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 480                                 // exist in the tool or the code was not compiled with the tool and
 481                                 // therefore the lint was never added to the `LintStore`. To detect
 482                                 // this is the responsibility of the lint tool.
 483                             }
 484                         }
 485                     }
 486
 487                     &CheckLintNameResult::NoTool => {
 488                         let mut err = struct_span_err!(
 489                             sess,
 490                             tool_ident.map_or(DUMMY_SP, |ident| ident.span),
 491                             E0710,
 492                             "unknown tool name `{}` found in scoped lint: `{}::{}`",
 493                             tool_name.unwrap(),
 494                             tool_name.unwrap(),
 495                             pprust::path_to_string(&meta_item.path),
 496                         );
 497                         if sess.is_nightly_build() {
 498                             err.help(&format!(
 499                                 "add `#![register_tool({})]` to the crate root",
 500                                 tool_name.unwrap()
 501                             ));
 502                         }
 503                         err.emit();
 504                         continue;
 505                     }
 506
 507                     _ if !self.warn_about_weird_lints => {}
 508
 509                     CheckLintNameResult::Warning(msg, renamed) => {
 510                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 511                         let (renamed_lint_level, src) = self.sets.get_lint_level(
 512                             lint,
 513                             self.cur,
 514                             Some(self.current_specs()),
 515                             &sess,
 516                         );
 517                         struct_lint_level(
 518                             self.sess,
 519                             lint,
 520                             renamed_lint_level,
 521                             src,
 522                             Some(sp.into()),
 523                             |lint| {
 524                                 let mut err = lint.build(&msg);
 525                                 if let Some(new_name) = &renamed {
 526                                     err.span_suggestion(
 527                                         sp,
 528                                         "use the new name",
 529                                         new_name,
 530                                         Applicability::MachineApplicable,
 531                                     );
 532                                 }
 533                                 err.emit();
 534                             },
 535                         );
 536                     }
 537                     CheckLintNameResult::NoLint(suggestion) => {
 538                         let lint = builtin::UNKNOWN_LINTS;
 539                         let (level, src) = self.sets.get_lint_level(
 540                             lint,
 541                             self.cur,
 542                             Some(self.current_specs()),
 543                             self.sess,
 544                         );
 545                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 546                             let name = if let Some(tool_ident) = tool_ident {
 547                                 format!("{}::{}", tool_ident.name, name)
 548                             } else {
 549                                 name.to_string()
 550                             };
 551                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 552                             if let Some(suggestion) = suggestion {
 553                                 db.span_suggestion(
 554                                     sp,
 555                                     "did you mean",
 556                                     suggestion,
 557                                     Applicability::MachineApplicable,
 558                                 );
 559                             }
 560                             db.emit();
 561                         });
 562                     }
 563                 }
 564                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 565                 // This happens outside of the match because the new lint should be applied even if
 566                 // we don't warn about the name change.
 567                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 568                     // Ignore any errors or warnings that happen because the new name is inaccurate
 569                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 570                     if let CheckLintNameResult::Ok(ids) =
 571                         self.store.check_lint_name(&new_name, None, self.registered_tools)
 572                     {
 573                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 574                         for &id in ids {
 575                             if self.check_gated_lint(id, attr.span) {
 576                                 self.insert_spec(id, (level, src));
 577                             }
 578                         }
 579                         if let Level::Expect(expect_id) = level {
 580                             self.lint_expectations.push((
 581                                 expect_id,
 582                                 LintExpectation::new(reason, sp, false, tool_name),
 583                             ));
 584                         }
 585                     } else {
 586                         panic!("renamed lint does not exist: {}", new_name);
 587                     }
 588                 }
 589             }
 590         }
 591
 592         if !is_crate_node {
 593             for (id, &(level, ref src)) in self.current_specs().iter() {
 594                 if !id.lint.crate_level_only {
 595                     continue;
 596                 }
 597
 598                 let LintLevelSource::Node(lint_attr_name, lint_attr_span, _) = *src else {
 599                     continue
 600                 };
 601
 602                 let lint = builtin::UNUSED_ATTRIBUTES;
 603                 let (lint_level, lint_src) =
 604                     self.sets.get_lint_level(lint, self.cur, Some(self.current_specs()), self.sess);
 605                 struct_lint_level(
 606                     self.sess,
 607                     lint,
 608                     lint_level,
 609                     lint_src,
 610                     Some(lint_attr_span.into()),
 611                     |lint| {
 612                         let mut db = lint.build(&format!(
 613                             "{}({}) is ignored unless specified at crate level",
 614                             level.as_str(),
 615                             lint_attr_name
 616                         ));
 617                         db.emit();
 618                     },
 619                 );
 620                 // don't set a separate error for every lint in the group
 621                 break;
 622             }
 623         }
 624
 625         if self.current_specs().is_empty() {
 626             self.sets.list.pop();
 627             self.cur = prev;
 628         }
 629
 630         BuilderPush { prev, changed: prev != self.cur }
 631     }
 632
 633     fn create_stable_id(
 634         &mut self,
 635         unstable_id: LintExpectationId,
 636         hir_id: HirId,
 637         attr_index: usize,
 638     ) -> LintExpectationId {
 639         let stable_id =
 640             LintExpectationId::Stable { hir_id, attr_index: attr_index as u16, lint_index: None };
 641
 642         self.expectation_id_map.insert(unstable_id, stable_id);
 643
 644         stable_id
 645     }
 646
 647     /// Checks if the lint is gated on a feature that is not enabled.
 648     ///
 649     /// Returns `true` if the lint's feature is enabled.
 650     fn check_gated_lint(&self, lint_id: LintId, span: Span) -> bool {
 651         if let Some(feature) = lint_id.lint.feature_gate {
 652             if !self.sess.features_untracked().enabled(feature) {
 653                 let lint = builtin::UNKNOWN_LINTS;
 654                 let (level, src) = self.lint_level(builtin::UNKNOWN_LINTS);
 655                 struct_lint_level(self.sess, lint, level, src, Some(span.into()), |lint_db| {
 656                     let mut db =
 657                         lint_db.build(&format!("unknown lint: `{}`", lint_id.lint.name_lower()));
 658                     db.note(&format!("the `{}` lint is unstable", lint_id.lint.name_lower(),));
 659                     add_feature_diagnostics(&mut db, &self.sess.parse_sess, feature);
 660                     db.emit();
 661                 });
 662                 return false;
 663             }
 664         }
 665         true
 666     }
 667
 668     /// Called after `push` when the scope of a set of attributes are exited.
 669     pub fn pop(&mut self, push: BuilderPush) {
 670         self.cur = push.prev;
 671     }
 672
 673     /// Find the lint level for a lint.
 674     pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
 675         self.sets.get_lint_level(lint, self.cur, None, self.sess)
 676     }
 677
 678     /// Used to emit a lint-related diagnostic based on the current state of
 679     /// this lint context.
 680     pub fn struct_lint(
 681         &self,
 682         lint: &'static Lint,
 683         span: Option<MultiSpan>,
 684         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 685     ) {
 686         let (level, src) = self.lint_level(lint);
 687         struct_lint_level(self.sess, lint, level, src, span, decorate)
 688     }
 689
 690     /// Registers the ID provided with the current set of lints stored in
 691     /// this context.
 692     pub fn register_id(&mut self, id: HirId) {
 693         self.id_to_set.insert(id, self.cur);
 694     }
 695
 696     fn update_unstable_expectation_ids(&self) {
 697         self.sess.diagnostic().update_unstable_expectation_id(&self.expectation_id_map);
 698     }
 699
 700     pub fn build_map(self) -> LintLevelMap {
 701         LintLevelMap {
 702             sets: self.sets,
 703             id_to_set: self.id_to_set,
 704             lint_expectations: self.lint_expectations,
 705         }
 706     }
 707 }
 708
 709 struct LintLevelMapBuilder<'tcx> {
 710     levels: LintLevelsBuilder<'tcx>,
 711     tcx: TyCtxt<'tcx>,
 712 }
 713
 714 impl LintLevelMapBuilder<'_> {
 715     fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
 716     where
 717         F: FnOnce(&mut Self),
 718     {
 719         let is_crate_hir = id == hir::CRATE_HIR_ID;
 720         let attrs = self.tcx.hir().attrs(id);
 721         let push = self.levels.push(attrs, is_crate_hir, Some(id));
 722
 723         if push.changed {
 724             self.levels.register_id(id);
 725         }
 726         f(self);
 727         self.levels.pop(push);
 728     }
 729 }
 730
 731 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
 732     type NestedFilter = nested_filter::All;
 733
 734     fn nested_visit_map(&mut self) -> Self::Map {
 735         self.tcx.hir()
 736     }
 737
 738     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 739         self.with_lint_attrs(param.hir_id, |builder| {
 740             intravisit::walk_param(builder, param);
 741         });
 742     }
 743
 744     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 745         self.with_lint_attrs(it.hir_id(), |builder| {
 746             intravisit::walk_item(builder, it);
 747         });
 748     }
 749
 750     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 751         self.with_lint_attrs(it.hir_id(), |builder| {
 752             intravisit::walk_foreign_item(builder, it);
 753         })
 754     }
 755
 756     fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
 757         // We will call `with_lint_attrs` when we walk
 758         // the `StmtKind`. The outer statement itself doesn't
 759         // define the lint levels.
 760         intravisit::walk_stmt(self, e);
 761     }
 762
 763     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 764         self.with_lint_attrs(e.hir_id, |builder| {
 765             intravisit::walk_expr(builder, e);
 766         })
 767     }
 768
 769     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
 770         self.with_lint_attrs(s.hir_id, |builder| {
 771             intravisit::walk_field_def(builder, s);
 772         })
 773     }
 774
 775     fn visit_variant(
 776         &mut self,
 777         v: &'tcx hir::Variant<'tcx>,
 778         g: &'tcx hir::Generics<'tcx>,
 779         item_id: hir::HirId,
 780     ) {
 781         self.with_lint_attrs(v.id, |builder| {
 782             intravisit::walk_variant(builder, v, g, item_id);
 783         })
 784     }
 785
 786     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 787         self.with_lint_attrs(l.hir_id, |builder| {
 788             intravisit::walk_local(builder, l);
 789         })
 790     }
 791
 792     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 793         self.with_lint_attrs(a.hir_id, |builder| {
 794             intravisit::walk_arm(builder, a);
 795         })
 796     }
 797
 798     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 799         self.with_lint_attrs(trait_item.hir_id(), |builder| {
 800             intravisit::walk_trait_item(builder, trait_item);
 801         });
 802     }
 803
 804     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 805         self.with_lint_attrs(impl_item.hir_id(), |builder| {
 806             intravisit::walk_impl_item(builder, impl_item);
 807         });
 808     }
 809 }
 810
 811 pub fn provide(providers: &mut Providers) {
 812     providers.lint_levels = lint_levels;
 813 }