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