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, DiagnosticBuilder};
   7 use rustc_hir as hir;
   8 use rustc_hir::{intravisit, HirId, CRATE_HIR_ID};
   9 use rustc_middle::hir::map::Map;
  10 use rustc_middle::lint::LevelAndSource;
  11 use rustc_middle::lint::LintDiagnosticBuilder;
  12 use rustc_middle::lint::{
  13     struct_lint_level, LintLevelMap, LintLevelSets, LintLevelSource, LintSet, LintStackIndex,
  14     COMMAND_LINE,
  15 };
  16 use rustc_middle::ty::query::Providers;
  17 use rustc_middle::ty::TyCtxt;
  18 use rustc_session::lint::{
  19     builtin::{self, FORBIDDEN_LINT_GROUPS},
  20     Level, Lint, LintId,
  21 };
  22 use rustc_session::parse::feature_err;
  23 use rustc_session::Session;
  24 use rustc_span::symbol::{sym, Symbol};
  25 use rustc_span::{source_map::MultiSpan, Span, DUMMY_SP};
  26 use tracing::debug;
  27
  28 fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
  29     let store = unerased_lint_store(tcx);
  30     let crate_attrs = tcx.hir().attrs(CRATE_HIR_ID);
  31     let levels = LintLevelsBuilder::new(tcx.sess, false, &store, crate_attrs);
  32     let mut builder = LintLevelMapBuilder { levels, tcx, store };
  33     let krate = tcx.hir().krate();
  34
  35     builder.levels.id_to_set.reserve(krate.owners.len() + 1);
  36
  37     let push = builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), &store, true);
  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.build_map()
  43 }
  44
  45 pub struct LintLevelsBuilder<'s> {
  46     sess: &'s Session,
  47     sets: LintLevelSets,
  48     id_to_set: FxHashMap<HirId, LintStackIndex>,
  49     cur: LintStackIndex,
  50     warn_about_weird_lints: bool,
  51     store: &'s LintStore,
  52     crate_attrs: &'s [ast::Attribute],
  53 }
  54
  55 pub struct BuilderPush {
  56     prev: LintStackIndex,
  57     pub changed: bool,
  58 }
  59
  60 impl<'s> LintLevelsBuilder<'s> {
  61     pub fn new(
  62         sess: &'s Session,
  63         warn_about_weird_lints: bool,
  64         store: &'s LintStore,
  65         crate_attrs: &'s [ast::Attribute],
  66     ) -> Self {
  67         let mut builder = LintLevelsBuilder {
  68             sess,
  69             sets: LintLevelSets::new(),
  70             cur: COMMAND_LINE,
  71             id_to_set: Default::default(),
  72             warn_about_weird_lints,
  73             store,
  74             crate_attrs,
  75         };
  76         builder.process_command_line(sess, store);
  77         assert_eq!(builder.sets.list.len(), 1);
  78         builder
  79     }
  80
  81     fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
  82         let mut specs = FxHashMap::default();
  83         self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
  84
  85         for &(ref lint_name, level) in &sess.opts.lint_opts {
  86             store.check_lint_name_cmdline(sess, &lint_name, level, self.crate_attrs);
  87             let orig_level = level;
  88             let lint_flag_val = Symbol::intern(lint_name);
  89
  90             let ids = match store.find_lints(&lint_name) {
  91                 Ok(ids) => ids,
  92                 Err(_) => continue, // errors handled in check_lint_name_cmdline above
  93             };
  94             for id in ids {
  95                 // ForceWarn and Forbid cannot be overriden
  96                 if let Some((Level::ForceWarn | Level::Forbid, _)) = specs.get(&id) {
  97                     continue;
  98                 }
  99
 100                 self.check_gated_lint(id, DUMMY_SP);
 101                 let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
 102                 specs.insert(id, (level, src));
 103             }
 104         }
 105
 106         self.cur = self.sets.list.push(LintSet { specs, parent: COMMAND_LINE });
 107     }
 108
 109     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
 110     /// (e.g. if a forbid was already inserted on the same scope), then emits a
 111     /// diagnostic with no change to `specs`.
 112     fn insert_spec(
 113         &mut self,
 114         specs: &mut FxHashMap<LintId, LevelAndSource>,
 115         id: LintId,
 116         (level, src): LevelAndSource,
 117     ) {
 118         let (old_level, old_src) =
 119             self.sets.get_lint_level(id.lint, self.cur, Some(&specs), &self.sess);
 120         // Setting to a non-forbid level is an error if the lint previously had
 121         // a forbid level. Note that this is not necessarily true even with a
 122         // `#[forbid(..)]` attribute present, as that is overriden by `--cap-lints`.
 123         //
 124         // This means that this only errors if we're truly lowering the lint
 125         // level from forbid.
 126         if level != Level::Forbid {
 127             if let Level::Forbid = old_level {
 128                 // Backwards compatibility check:
 129                 //
 130                 // We used to not consider `forbid(lint_group)`
 131                 // as preventing `allow(lint)` for some lint `lint` in
 132                 // `lint_group`. For now, issue a future-compatibility
 133                 // warning for this case.
 134                 let id_name = id.lint.name_lower();
 135                 let fcw_warning = match old_src {
 136                     LintLevelSource::Default => false,
 137                     LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
 138                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
 139                 };
 140                 debug!(
 141                     "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
 142                     fcw_warning, specs, old_src, id_name
 143                 );
 144
 145                 let decorate_diag_builder = |mut diag_builder: DiagnosticBuilder<'_>| {
 146                     diag_builder.span_label(src.span(), "overruled by previous forbid");
 147                     match old_src {
 148                         LintLevelSource::Default => {
 149                             diag_builder.note(&format!(
 150                                 "`forbid` lint level is the default for {}",
 151                                 id.to_string()
 152                             ));
 153                         }
 154                         LintLevelSource::Node(_, forbid_source_span, reason) => {
 155                             diag_builder.span_label(forbid_source_span, "`forbid` level set here");
 156                             if let Some(rationale) = reason {
 157                                 diag_builder.note(&rationale.as_str());
 158                             }
 159                         }
 160                         LintLevelSource::CommandLine(_, _) => {
 161                             diag_builder.note("`forbid` lint level was set on command line");
 162                         }
 163                     }
 164                     diag_builder.emit();
 165                 };
 166                 if !fcw_warning {
 167                     let diag_builder = struct_span_err!(
 168                         self.sess,
 169                         src.span(),
 170                         E0453,
 171                         "{}({}) incompatible with previous forbid",
 172                         level.as_str(),
 173                         src.name(),
 174                     );
 175                     decorate_diag_builder(diag_builder);
 176                 } else {
 177                     self.struct_lint(
 178                         FORBIDDEN_LINT_GROUPS,
 179                         Some(src.span().into()),
 180                         |diag_builder| {
 181                             let diag_builder = diag_builder.build(&format!(
 182                                 "{}({}) incompatible with previous forbid",
 183                                 level.as_str(),
 184                                 src.name(),
 185                             ));
 186                             decorate_diag_builder(diag_builder);
 187                         },
 188                     );
 189                 }
 190
 191                 // Retain the forbid lint level, unless we are
 192                 // issuing a FCW. In the FCW case, we want to
 193                 // respect the new setting.
 194                 if !fcw_warning {
 195                     return;
 196                 }
 197             }
 198         }
 199         if let Level::ForceWarn = old_level {
 200             specs.insert(id, (old_level, old_src));
 201         } else {
 202             specs.insert(id, (level, src));
 203         }
 204     }
 205
 206     /// Pushes a list of AST lint attributes onto this context.
 207     ///
 208     /// This function will return a `BuilderPush` object which should be passed
 209     /// to `pop` when this scope for the attributes provided is exited.
 210     ///
 211     /// This function will perform a number of tasks:
 212     ///
 213     /// * It'll validate all lint-related attributes in `attrs`
 214     /// * It'll mark all lint-related attributes as used
 215     /// * Lint levels will be updated based on the attributes provided
 216     /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
 217     ///   `#[allow]`
 218     ///
 219     /// Don't forget to call `pop`!
 220     pub(crate) fn push(
 221         &mut self,
 222         attrs: &[ast::Attribute],
 223         store: &LintStore,
 224         is_crate_node: bool,
 225     ) -> BuilderPush {
 226         let mut specs = FxHashMap::default();
 227         let sess = self.sess;
 228         let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
 229         for attr in attrs {
 230             let Some(level) = Level::from_symbol(attr.name_or_empty()) else {
 231                 continue
 232             };
 233
 234             let Some(mut metas) = attr.meta_item_list() else {
 235                 continue
 236             };
 237
 238             if metas.is_empty() {
 239                 // FIXME (#55112): issue unused-attributes lint for `#[level()]`
 240                 continue;
 241             }
 242
 243             // Before processing the lint names, look for a reason (RFC 2383)
 244             // at the end.
 245             let mut reason = None;
 246             let tail_li = &metas[metas.len() - 1];
 247             if let Some(item) = tail_li.meta_item() {
 248                 match item.kind {
 249                     ast::MetaItemKind::Word => {} // actual lint names handled later
 250                     ast::MetaItemKind::NameValue(ref name_value) => {
 251                         if item.path == sym::reason {
 252                             // FIXME (#55112): issue unused-attributes lint if we thereby
 253                             // don't have any lint names (`#[level(reason = "foo")]`)
 254                             if let ast::LitKind::Str(rationale, _) = name_value.kind {
 255                                 if !self.sess.features_untracked().lint_reasons {
 256                                     feature_err(
 257                                         &self.sess.parse_sess,
 258                                         sym::lint_reasons,
 259                                         item.span,
 260                                         "lint reasons are experimental",
 261                                     )
 262                                     .emit();
 263                                 }
 264                                 reason = Some(rationale);
 265                             } else {
 266                                 bad_attr(name_value.span)
 267                                     .span_label(name_value.span, "reason must be a string literal")
 268                                     .emit();
 269                             }
 270                             // found reason, reslice meta list to exclude it
 271                             metas.pop().unwrap();
 272                         } else {
 273                             bad_attr(item.span)
 274                                 .span_label(item.span, "bad attribute argument")
 275                                 .emit();
 276                         }
 277                     }
 278                     ast::MetaItemKind::List(_) => {
 279                         bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
 280                     }
 281                 }
 282             }
 283
 284             for li in metas {
 285                 let sp = li.span();
 286                 let mut meta_item = match li {
 287                     ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
 288                     _ => {
 289                         let mut err = bad_attr(sp);
 290                         let mut add_label = true;
 291                         if let Some(item) = li.meta_item() {
 292                             if let ast::MetaItemKind::NameValue(_) = item.kind {
 293                                 if item.path == sym::reason {
 294                                     err.span_label(sp, "reason in lint attribute must come last");
 295                                     add_label = false;
 296                                 }
 297                             }
 298                         }
 299                         if add_label {
 300                             err.span_label(sp, "bad attribute argument");
 301                         }
 302                         err.emit();
 303                         continue;
 304                     }
 305                 };
 306                 let tool_ident = if meta_item.path.segments.len() > 1 {
 307                     Some(meta_item.path.segments.remove(0).ident)
 308                 } else {
 309                     None
 310                 };
 311                 let tool_name = tool_ident.map(|ident| ident.name);
 312                 let name = pprust::path_to_string(&meta_item.path);
 313                 let lint_result = store.check_lint_name(sess, &name, tool_name, self.crate_attrs);
 314                 match &lint_result {
 315                     CheckLintNameResult::Ok(ids) => {
 316                         let src = LintLevelSource::Node(
 317                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 318                             sp,
 319                             reason,
 320                         );
 321                         for &id in *ids {
 322                             self.check_gated_lint(id, attr.span);
 323                             self.insert_spec(&mut specs, id, (level, src));
 324                         }
 325                     }
 326
 327                     CheckLintNameResult::Tool(result) => {
 328                         match *result {
 329                             Ok(ids) => {
 330                                 let complete_name =
 331                                     &format!("{}::{}", tool_ident.unwrap().name, name);
 332                                 let src = LintLevelSource::Node(
 333                                     Symbol::intern(complete_name),
 334                                     sp,
 335                                     reason,
 336                                 );
 337                                 for id in ids {
 338                                     self.insert_spec(&mut specs, *id, (level, src));
 339                                 }
 340                             }
 341                             Err((Some(ids), ref new_lint_name)) => {
 342                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 343                                 let (lvl, src) =
 344                                     self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 345                                 struct_lint_level(
 346                                     self.sess,
 347                                     lint,
 348                                     lvl,
 349                                     src,
 350                                     Some(sp.into()),
 351                                     |lint| {
 352                                         let msg = format!(
 353                                             "lint name `{}` is deprecated \
 354                                              and may not have an effect in the future.",
 355                                             name
 356                                         );
 357                                         lint.build(&msg)
 358                                             .span_suggestion(
 359                                                 sp,
 360                                                 "change it to",
 361                                                 new_lint_name.to_string(),
 362                                                 Applicability::MachineApplicable,
 363                                             )
 364                                             .emit();
 365                                     },
 366                                 );
 367
 368                                 let src = LintLevelSource::Node(
 369                                     Symbol::intern(&new_lint_name),
 370                                     sp,
 371                                     reason,
 372                                 );
 373                                 for id in ids {
 374                                     self.insert_spec(&mut specs, *id, (level, src));
 375                                 }
 376                             }
 377                             Err((None, _)) => {
 378                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 379                                 // exist in the tool or the code was not compiled with the tool and
 380                                 // therefore the lint was never added to the `LintStore`. To detect
 381                                 // this is the responsibility of the lint tool.
 382                             }
 383                         }
 384                     }
 385
 386                     &CheckLintNameResult::NoTool => {
 387                         let mut err = struct_span_err!(
 388                             sess,
 389                             tool_ident.map_or(DUMMY_SP, |ident| ident.span),
 390                             E0710,
 391                             "unknown tool name `{}` found in scoped lint: `{}::{}`",
 392                             tool_name.unwrap(),
 393                             tool_name.unwrap(),
 394                             pprust::path_to_string(&meta_item.path),
 395                         );
 396                         if sess.is_nightly_build() {
 397                             err.help(&format!(
 398                                 "add `#![register_tool({})]` to the crate root",
 399                                 tool_name.unwrap()
 400                             ));
 401                         }
 402                         err.emit();
 403                         continue;
 404                     }
 405
 406                     _ if !self.warn_about_weird_lints => {}
 407
 408                     CheckLintNameResult::Warning(msg, renamed) => {
 409                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 410                         let (renamed_lint_level, src) =
 411                             self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 412                         struct_lint_level(
 413                             self.sess,
 414                             lint,
 415                             renamed_lint_level,
 416                             src,
 417                             Some(sp.into()),
 418                             |lint| {
 419                                 let mut err = lint.build(&msg);
 420                                 if let Some(new_name) = &renamed {
 421                                     err.span_suggestion(
 422                                         sp,
 423                                         "use the new name",
 424                                         new_name.to_string(),
 425                                         Applicability::MachineApplicable,
 426                                     );
 427                                 }
 428                                 err.emit();
 429                             },
 430                         );
 431                     }
 432                     CheckLintNameResult::NoLint(suggestion) => {
 433                         let lint = builtin::UNKNOWN_LINTS;
 434                         let (level, src) =
 435                             self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 436                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 437                             let name = if let Some(tool_ident) = tool_ident {
 438                                 format!("{}::{}", tool_ident.name, name)
 439                             } else {
 440                                 name.to_string()
 441                             };
 442                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 443                             if let Some(suggestion) = suggestion {
 444                                 db.span_suggestion(
 445                                     sp,
 446                                     "did you mean",
 447                                     suggestion.to_string(),
 448                                     Applicability::MachineApplicable,
 449                                 );
 450                             }
 451                             db.emit();
 452                         });
 453                     }
 454                 }
 455                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 456                 // This happens outside of the match because the new lint should be applied even if
 457                 // we don't warn about the name change.
 458                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 459                     // Ignore any errors or warnings that happen because the new name is inaccurate
 460                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 461                     if let CheckLintNameResult::Ok(ids) =
 462                         store.check_lint_name(sess, &new_name, None, self.crate_attrs)
 463                     {
 464                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 465                         for &id in ids {
 466                             self.check_gated_lint(id, attr.span);
 467                             self.insert_spec(&mut specs, id, (level, src));
 468                         }
 469                     } else {
 470                         panic!("renamed lint does not exist: {}", new_name);
 471                     }
 472                 }
 473             }
 474         }
 475
 476         if !is_crate_node {
 477             for (id, &(level, ref src)) in specs.iter() {
 478                 if !id.lint.crate_level_only {
 479                     continue;
 480                 }
 481
 482                 let LintLevelSource::Node(lint_attr_name, lint_attr_span, _) = *src else {
 483                     continue
 484                 };
 485
 486                 let lint = builtin::UNUSED_ATTRIBUTES;
 487                 let (lint_level, lint_src) =
 488                     self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 489                 struct_lint_level(
 490                     self.sess,
 491                     lint,
 492                     lint_level,
 493                     lint_src,
 494                     Some(lint_attr_span.into()),
 495                     |lint| {
 496                         let mut db = lint.build(&format!(
 497                             "{}({}) is ignored unless specified at crate level",
 498                             level.as_str(),
 499                             lint_attr_name
 500                         ));
 501                         db.emit();
 502                     },
 503                 );
 504                 // don't set a separate error for every lint in the group
 505                 break;
 506             }
 507         }
 508
 509         let prev = self.cur;
 510         if !specs.is_empty() {
 511             self.cur = self.sets.list.push(LintSet { specs, parent: prev });
 512         }
 513
 514         BuilderPush { prev, changed: prev != self.cur }
 515     }
 516
 517     /// Checks if the lint is gated on a feature that is not enabled.
 518     fn check_gated_lint(&self, lint_id: LintId, span: Span) {
 519         if let Some(feature) = lint_id.lint.feature_gate {
 520             if !self.sess.features_untracked().enabled(feature) {
 521                 feature_err(
 522                     &self.sess.parse_sess,
 523                     feature,
 524                     span,
 525                     &format!("the `{}` lint is unstable", lint_id.lint.name_lower()),
 526                 )
 527                 .emit();
 528             }
 529         }
 530     }
 531
 532     /// Called after `push` when the scope of a set of attributes are exited.
 533     pub fn pop(&mut self, push: BuilderPush) {
 534         self.cur = push.prev;
 535     }
 536
 537     /// Find the lint level for a lint.
 538     pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
 539         self.sets.get_lint_level(lint, self.cur, None, self.sess)
 540     }
 541
 542     /// Used to emit a lint-related diagnostic based on the current state of
 543     /// this lint context.
 544     pub fn struct_lint(
 545         &self,
 546         lint: &'static Lint,
 547         span: Option<MultiSpan>,
 548         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 549     ) {
 550         let (level, src) = self.lint_level(lint);
 551         struct_lint_level(self.sess, lint, level, src, span, decorate)
 552     }
 553
 554     /// Registers the ID provided with the current set of lints stored in
 555     /// this context.
 556     pub fn register_id(&mut self, id: HirId) {
 557         self.id_to_set.insert(id, self.cur);
 558     }
 559
 560     pub fn build_map(self) -> LintLevelMap {
 561         LintLevelMap { sets: self.sets, id_to_set: self.id_to_set }
 562     }
 563 }
 564
 565 pub fn is_known_lint_tool(m_item: Symbol, sess: &Session, attrs: &[ast::Attribute]) -> bool {
 566     if [sym::clippy, sym::rustc, sym::rustdoc].contains(&m_item) {
 567         return true;
 568     }
 569     // Look for registered tools
 570     // NOTE: does no error handling; error handling is done by rustc_resolve.
 571     sess.filter_by_name(attrs, sym::register_tool)
 572         .filter_map(|attr| attr.meta_item_list())
 573         .flatten()
 574         .filter_map(|nested_meta| nested_meta.ident())
 575         .map(|ident| ident.name)
 576         .any(|name| name == m_item)
 577 }
 578
 579 struct LintLevelMapBuilder<'a, 'tcx> {
 580     levels: LintLevelsBuilder<'tcx>,
 581     tcx: TyCtxt<'tcx>,
 582     store: &'a LintStore,
 583 }
 584
 585 impl LintLevelMapBuilder<'_, '_> {
 586     fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
 587     where
 588         F: FnOnce(&mut Self),
 589     {
 590         let is_crate_hir = id == hir::CRATE_HIR_ID;
 591         let attrs = self.tcx.hir().attrs(id);
 592         let push = self.levels.push(attrs, self.store, is_crate_hir);
 593         if push.changed {
 594             self.levels.register_id(id);
 595         }
 596         f(self);
 597         self.levels.pop(push);
 598     }
 599 }
 600
 601 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
 602     type Map = Map<'tcx>;
 603
 604     fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
 605         intravisit::NestedVisitorMap::All(self.tcx.hir())
 606     }
 607
 608     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 609         self.with_lint_attrs(param.hir_id, |builder| {
 610             intravisit::walk_param(builder, param);
 611         });
 612     }
 613
 614     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 615         self.with_lint_attrs(it.hir_id(), |builder| {
 616             intravisit::walk_item(builder, it);
 617         });
 618     }
 619
 620     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 621         self.with_lint_attrs(it.hir_id(), |builder| {
 622             intravisit::walk_foreign_item(builder, it);
 623         })
 624     }
 625
 626     fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
 627         // We will call `with_lint_attrs` when we walk
 628         // the `StmtKind`. The outer statement itself doesn't
 629         // define the lint levels.
 630         intravisit::walk_stmt(self, e);
 631     }
 632
 633     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 634         self.with_lint_attrs(e.hir_id, |builder| {
 635             intravisit::walk_expr(builder, e);
 636         })
 637     }
 638
 639     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
 640         self.with_lint_attrs(s.hir_id, |builder| {
 641             intravisit::walk_field_def(builder, s);
 642         })
 643     }
 644
 645     fn visit_variant(
 646         &mut self,
 647         v: &'tcx hir::Variant<'tcx>,
 648         g: &'tcx hir::Generics<'tcx>,
 649         item_id: hir::HirId,
 650     ) {
 651         self.with_lint_attrs(v.id, |builder| {
 652             intravisit::walk_variant(builder, v, g, item_id);
 653         })
 654     }
 655
 656     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 657         self.with_lint_attrs(l.hir_id, |builder| {
 658             intravisit::walk_local(builder, l);
 659         })
 660     }
 661
 662     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 663         self.with_lint_attrs(a.hir_id, |builder| {
 664             intravisit::walk_arm(builder, a);
 665         })
 666     }
 667
 668     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 669         self.with_lint_attrs(trait_item.hir_id(), |builder| {
 670             intravisit::walk_trait_item(builder, trait_item);
 671         });
 672     }
 673
 674     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 675         self.with_lint_attrs(impl_item.hir_id(), |builder| {
 676             intravisit::walk_impl_item(builder, impl_item);
 677         });
 678     }
 679 }
 680
 681 pub fn provide(providers: &mut Providers) {
 682     providers.lint_levels = lint_levels;
 683 }