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::unwrap_or;
   5 use rustc_ast_pretty::pprust;
   6 use rustc_data_structures::fx::FxHashMap;
   7 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
   8 use rustc_hir as hir;
   9 use rustc_hir::{intravisit, HirId, CRATE_HIR_ID};
  10 use rustc_middle::hir::map::Map;
  11 use rustc_middle::lint::LevelAndSource;
  12 use rustc_middle::lint::LintDiagnosticBuilder;
  13 use rustc_middle::lint::{
  14     struct_lint_level, LintLevelMap, LintLevelSets, LintLevelSource, LintSet, LintStackIndex,
  15     COMMAND_LINE,
  16 };
  17 use rustc_middle::ty::query::Providers;
  18 use rustc_middle::ty::TyCtxt;
  19 use rustc_session::lint::{
  20     builtin::{self, FORBIDDEN_LINT_GROUPS},
  21     Level, Lint, LintId,
  22 };
  23 use rustc_session::parse::feature_err;
  24 use rustc_session::Session;
  25 use rustc_span::symbol::{sym, Symbol};
  26 use rustc_span::{source_map::MultiSpan, Span, DUMMY_SP};
  27 use tracing::debug;
  28
  29 fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
  30     let store = unerased_lint_store(tcx);
  31     let crate_attrs = tcx.hir().attrs(CRATE_HIR_ID);
  32     let levels = LintLevelsBuilder::new(tcx.sess, false, &store, crate_attrs);
  33     let mut builder = LintLevelMapBuilder { levels, tcx, store };
  34     let krate = tcx.hir().krate();
  35
  36     builder.levels.id_to_set.reserve(krate.owners.len() + 1);
  37
  38     let push = builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), &store, true);
  39     builder.levels.register_id(hir::CRATE_HIR_ID);
  40     for macro_def in krate.exported_macros() {
  41         builder.levels.register_id(macro_def.hir_id());
  42     }
  43     intravisit::walk_crate(&mut builder, krate);
  44     builder.levels.pop(push);
  45
  46     builder.levels.build_map()
  47 }
  48
  49 pub struct LintLevelsBuilder<'s> {
  50     sess: &'s Session,
  51     sets: LintLevelSets,
  52     id_to_set: FxHashMap<HirId, LintStackIndex>,
  53     cur: LintStackIndex,
  54     warn_about_weird_lints: bool,
  55     store: &'s LintStore,
  56     crate_attrs: &'s [ast::Attribute],
  57 }
  58
  59 pub struct BuilderPush {
  60     prev: LintStackIndex,
  61     pub changed: bool,
  62 }
  63
  64 impl<'s> LintLevelsBuilder<'s> {
  65     pub fn new(
  66         sess: &'s Session,
  67         warn_about_weird_lints: bool,
  68         store: &'s LintStore,
  69         crate_attrs: &'s [ast::Attribute],
  70     ) -> Self {
  71         let mut builder = LintLevelsBuilder {
  72             sess,
  73             sets: LintLevelSets::new(),
  74             cur: COMMAND_LINE,
  75             id_to_set: Default::default(),
  76             warn_about_weird_lints,
  77             store,
  78             crate_attrs,
  79         };
  80         builder.process_command_line(sess, store);
  81         assert_eq!(builder.sets.list.len(), 1);
  82         builder
  83     }
  84
  85     fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
  86         let mut specs = FxHashMap::default();
  87         self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
  88
  89         for &(ref lint_name, level) in &sess.opts.lint_opts {
  90             store.check_lint_name_cmdline(sess, &lint_name, level, self.crate_attrs);
  91             let orig_level = level;
  92             let lint_flag_val = Symbol::intern(lint_name);
  93
  94             let ids = match store.find_lints(&lint_name) {
  95                 Ok(ids) => ids,
  96                 Err(_) => continue, // errors handled in check_lint_name_cmdline above
  97             };
  98             for id in ids {
  99                 // ForceWarn and Forbid cannot be overriden
 100                 if let Some((Level::ForceWarn | Level::Forbid, _)) = specs.get(&id) {
 101                     continue;
 102                 }
 103
 104                 self.check_gated_lint(id, DUMMY_SP);
 105                 let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
 106                 specs.insert(id, (level, src));
 107             }
 108         }
 109
 110         self.cur = self.sets.list.push(LintSet { specs, parent: COMMAND_LINE });
 111     }
 112
 113     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
 114     /// (e.g. if a forbid was already inserted on the same scope), then emits a
 115     /// diagnostic with no change to `specs`.
 116     fn insert_spec(
 117         &mut self,
 118         specs: &mut FxHashMap<LintId, LevelAndSource>,
 119         id: LintId,
 120         (level, src): LevelAndSource,
 121     ) {
 122         let (old_level, old_src) =
 123             self.sets.get_lint_level(id.lint, self.cur, Some(&specs), &self.sess);
 124         // Setting to a non-forbid level is an error if the lint previously had
 125         // a forbid level. Note that this is not necessarily true even with a
 126         // `#[forbid(..)]` attribute present, as that is overriden by `--cap-lints`.
 127         //
 128         // This means that this only errors if we're truly lowering the lint
 129         // level from forbid.
 130         if level != Level::Forbid {
 131             if let Level::Forbid = old_level {
 132                 // Backwards compatibility check:
 133                 //
 134                 // We used to not consider `forbid(lint_group)`
 135                 // as preventing `allow(lint)` for some lint `lint` in
 136                 // `lint_group`. For now, issue a future-compatibility
 137                 // warning for this case.
 138                 let id_name = id.lint.name_lower();
 139                 let fcw_warning = match old_src {
 140                     LintLevelSource::Default => false,
 141                     LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
 142                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
 143                 };
 144                 debug!(
 145                     "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
 146                     fcw_warning, specs, old_src, id_name
 147                 );
 148
 149                 let decorate_diag_builder = |mut diag_builder: DiagnosticBuilder<'_>| {
 150                     diag_builder.span_label(src.span(), "overruled by previous forbid");
 151                     match old_src {
 152                         LintLevelSource::Default => {
 153                             diag_builder.note(&format!(
 154                                 "`forbid` lint level is the default for {}",
 155                                 id.to_string()
 156                             ));
 157                         }
 158                         LintLevelSource::Node(_, forbid_source_span, reason) => {
 159                             diag_builder.span_label(forbid_source_span, "`forbid` level set here");
 160                             if let Some(rationale) = reason {
 161                                 diag_builder.note(&rationale.as_str());
 162                             }
 163                         }
 164                         LintLevelSource::CommandLine(_, _) => {
 165                             diag_builder.note("`forbid` lint level was set on command line");
 166                         }
 167                     }
 168                     diag_builder.emit();
 169                 };
 170                 if !fcw_warning {
 171                     let diag_builder = struct_span_err!(
 172                         self.sess,
 173                         src.span(),
 174                         E0453,
 175                         "{}({}) incompatible with previous forbid",
 176                         level.as_str(),
 177                         src.name(),
 178                     );
 179                     decorate_diag_builder(diag_builder);
 180                 } else {
 181                     self.struct_lint(
 182                         FORBIDDEN_LINT_GROUPS,
 183                         Some(src.span().into()),
 184                         |diag_builder| {
 185                             let diag_builder = diag_builder.build(&format!(
 186                                 "{}({}) incompatible with previous forbid",
 187                                 level.as_str(),
 188                                 src.name(),
 189                             ));
 190                             decorate_diag_builder(diag_builder);
 191                         },
 192                     );
 193                 }
 194
 195                 // Retain the forbid lint level, unless we are
 196                 // issuing a FCW. In the FCW case, we want to
 197                 // respect the new setting.
 198                 if !fcw_warning {
 199                     return;
 200                 }
 201             }
 202         }
 203         if let Level::ForceWarn = old_level {
 204             specs.insert(id, (old_level, old_src));
 205         } else {
 206             specs.insert(id, (level, src));
 207         }
 208     }
 209
 210     /// Pushes a list of AST lint attributes onto this context.
 211     ///
 212     /// This function will return a `BuilderPush` object which should be passed
 213     /// to `pop` when this scope for the attributes provided is exited.
 214     ///
 215     /// This function will perform a number of tasks:
 216     ///
 217     /// * It'll validate all lint-related attributes in `attrs`
 218     /// * It'll mark all lint-related attributes as used
 219     /// * Lint levels will be updated based on the attributes provided
 220     /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
 221     ///   `#[allow]`
 222     ///
 223     /// Don't forget to call `pop`!
 224     pub(crate) fn push(
 225         &mut self,
 226         attrs: &[ast::Attribute],
 227         store: &LintStore,
 228         is_crate_node: bool,
 229     ) -> BuilderPush {
 230         let mut specs = FxHashMap::default();
 231         let sess = self.sess;
 232         let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
 233         for attr in attrs {
 234             let level = match Level::from_symbol(attr.name_or_empty()) {
 235                 None => continue,
 236                 Some(lvl) => lvl,
 237             };
 238
 239             self.sess.mark_attr_used(attr);
 240
 241             let mut metas = unwrap_or!(attr.meta_item_list(), continue);
 242
 243             if metas.is_empty() {
 244                 // FIXME (#55112): issue unused-attributes lint for `#[level()]`
 245                 continue;
 246             }
 247
 248             // Before processing the lint names, look for a reason (RFC 2383)
 249             // at the end.
 250             let mut reason = None;
 251             let tail_li = &metas[metas.len() - 1];
 252             if let Some(item) = tail_li.meta_item() {
 253                 match item.kind {
 254                     ast::MetaItemKind::Word => {} // actual lint names handled later
 255                     ast::MetaItemKind::NameValue(ref name_value) => {
 256                         if item.path == sym::reason {
 257                             // FIXME (#55112): issue unused-attributes lint if we thereby
 258                             // don't have any lint names (`#[level(reason = "foo")]`)
 259                             if let ast::LitKind::Str(rationale, _) = name_value.kind {
 260                                 if !self.sess.features_untracked().lint_reasons {
 261                                     feature_err(
 262                                         &self.sess.parse_sess,
 263                                         sym::lint_reasons,
 264                                         item.span,
 265                                         "lint reasons are experimental",
 266                                     )
 267                                     .emit();
 268                                 }
 269                                 reason = Some(rationale);
 270                             } else {
 271                                 bad_attr(name_value.span)
 272                                     .span_label(name_value.span, "reason must be a string literal")
 273                                     .emit();
 274                             }
 275                             // found reason, reslice meta list to exclude it
 276                             metas.pop().unwrap();
 277                         } else {
 278                             bad_attr(item.span)
 279                                 .span_label(item.span, "bad attribute argument")
 280                                 .emit();
 281                         }
 282                     }
 283                     ast::MetaItemKind::List(_) => {
 284                         bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
 285                     }
 286                 }
 287             }
 288
 289             for li in metas {
 290                 let sp = li.span();
 291                 let mut meta_item = match li {
 292                     ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
 293                     _ => {
 294                         let mut err = bad_attr(sp);
 295                         let mut add_label = true;
 296                         if let Some(item) = li.meta_item() {
 297                             if let ast::MetaItemKind::NameValue(_) = item.kind {
 298                                 if item.path == sym::reason {
 299                                     err.span_label(sp, "reason in lint attribute must come last");
 300                                     add_label = false;
 301                                 }
 302                             }
 303                         }
 304                         if add_label {
 305                             err.span_label(sp, "bad attribute argument");
 306                         }
 307                         err.emit();
 308                         continue;
 309                     }
 310                 };
 311                 let tool_ident = if meta_item.path.segments.len() > 1 {
 312                     Some(meta_item.path.segments.remove(0).ident)
 313                 } else {
 314                     None
 315                 };
 316                 let tool_name = tool_ident.map(|ident| ident.name);
 317                 let name = pprust::path_to_string(&meta_item.path);
 318                 let lint_result = store.check_lint_name(sess, &name, tool_name, self.crate_attrs);
 319                 match &lint_result {
 320                     CheckLintNameResult::Ok(ids) => {
 321                         let src = LintLevelSource::Node(
 322                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 323                             sp,
 324                             reason,
 325                         );
 326                         for &id in *ids {
 327                             self.check_gated_lint(id, attr.span);
 328                             self.insert_spec(&mut specs, id, (level, src));
 329                         }
 330                     }
 331
 332                     CheckLintNameResult::Tool(result) => {
 333                         match *result {
 334                             Ok(ids) => {
 335                                 let complete_name =
 336                                     &format!("{}::{}", tool_ident.unwrap().name, name);
 337                                 let src = LintLevelSource::Node(
 338                                     Symbol::intern(complete_name),
 339                                     sp,
 340                                     reason,
 341                                 );
 342                                 for id in ids {
 343                                     self.insert_spec(&mut specs, *id, (level, src));
 344                                 }
 345                             }
 346                             Err((Some(ids), ref new_lint_name)) => {
 347                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 348                                 let (lvl, src) =
 349                                     self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 350                                 struct_lint_level(
 351                                     self.sess,
 352                                     lint,
 353                                     lvl,
 354                                     src,
 355                                     Some(sp.into()),
 356                                     |lint| {
 357                                         let msg = format!(
 358                                             "lint name `{}` is deprecated \
 359                                              and may not have an effect in the future.",
 360                                             name
 361                                         );
 362                                         lint.build(&msg)
 363                                             .span_suggestion(
 364                                                 sp,
 365                                                 "change it to",
 366                                                 new_lint_name.to_string(),
 367                                                 Applicability::MachineApplicable,
 368                                             )
 369                                             .emit();
 370                                     },
 371                                 );
 372
 373                                 let src = LintLevelSource::Node(
 374                                     Symbol::intern(&new_lint_name),
 375                                     sp,
 376                                     reason,
 377                                 );
 378                                 for id in ids {
 379                                     self.insert_spec(&mut specs, *id, (level, src));
 380                                 }
 381                             }
 382                             Err((None, _)) => {
 383                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 384                                 // exist in the tool or the code was not compiled with the tool and
 385                                 // therefore the lint was never added to the `LintStore`. To detect
 386                                 // this is the responsibility of the lint tool.
 387                             }
 388                         }
 389                     }
 390
 391                     &CheckLintNameResult::NoTool => {
 392                         let mut err = struct_span_err!(
 393                             sess,
 394                             tool_ident.map_or(DUMMY_SP, |ident| ident.span),
 395                             E0710,
 396                             "unknown tool name `{}` found in scoped lint: `{}::{}`",
 397                             tool_name.unwrap(),
 398                             tool_name.unwrap(),
 399                             pprust::path_to_string(&meta_item.path),
 400                         );
 401                         if sess.is_nightly_build() {
 402                             err.help(&format!(
 403                                 "add `#![register_tool({})]` to the crate root",
 404                                 tool_name.unwrap()
 405                             ));
 406                         }
 407                         err.emit();
 408                         continue;
 409                     }
 410
 411                     _ if !self.warn_about_weird_lints => {}
 412
 413                     CheckLintNameResult::Warning(msg, renamed) => {
 414                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 415                         let (renamed_lint_level, src) =
 416                             self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 417                         struct_lint_level(
 418                             self.sess,
 419                             lint,
 420                             renamed_lint_level,
 421                             src,
 422                             Some(sp.into()),
 423                             |lint| {
 424                                 let mut err = lint.build(&msg);
 425                                 if let Some(new_name) = &renamed {
 426                                     err.span_suggestion(
 427                                         sp,
 428                                         "use the new name",
 429                                         new_name.to_string(),
 430                                         Applicability::MachineApplicable,
 431                                     );
 432                                 }
 433                                 err.emit();
 434                             },
 435                         );
 436                     }
 437                     CheckLintNameResult::NoLint(suggestion) => {
 438                         let lint = builtin::UNKNOWN_LINTS;
 439                         let (level, src) =
 440                             self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 441                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 442                             let name = if let Some(tool_ident) = tool_ident {
 443                                 format!("{}::{}", tool_ident.name, name)
 444                             } else {
 445                                 name.to_string()
 446                             };
 447                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 448                             if let Some(suggestion) = suggestion {
 449                                 db.span_suggestion(
 450                                     sp,
 451                                     "did you mean",
 452                                     suggestion.to_string(),
 453                                     Applicability::MachineApplicable,
 454                                 );
 455                             }
 456                             db.emit();
 457                         });
 458                     }
 459                 }
 460                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 461                 // This happens outside of the match because the new lint should be applied even if
 462                 // we don't warn about the name change.
 463                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 464                     // Ignore any errors or warnings that happen because the new name is inaccurate
 465                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 466                     if let CheckLintNameResult::Ok(ids) =
 467                         store.check_lint_name(sess, &new_name, None, self.crate_attrs)
 468                     {
 469                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 470                         for &id in ids {
 471                             self.check_gated_lint(id, attr.span);
 472                             self.insert_spec(&mut specs, id, (level, src));
 473                         }
 474                     } else {
 475                         panic!("renamed lint does not exist: {}", new_name);
 476                     }
 477                 }
 478             }
 479         }
 480
 481         if !is_crate_node {
 482             for (id, &(level, ref src)) in specs.iter() {
 483                 if !id.lint.crate_level_only {
 484                     continue;
 485                 }
 486
 487                 let (lint_attr_name, lint_attr_span) = match *src {
 488                     LintLevelSource::Node(name, span, _) => (name, span),
 489                     _ => continue,
 490                 };
 491
 492                 let lint = builtin::UNUSED_ATTRIBUTES;
 493                 let (lint_level, lint_src) =
 494                     self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 495                 struct_lint_level(
 496                     self.sess,
 497                     lint,
 498                     lint_level,
 499                     lint_src,
 500                     Some(lint_attr_span.into()),
 501                     |lint| {
 502                         let mut db = lint.build(&format!(
 503                             "{}({}) is ignored unless specified at crate level",
 504                             level.as_str(),
 505                             lint_attr_name
 506                         ));
 507                         db.emit();
 508                     },
 509                 );
 510                 // don't set a separate error for every lint in the group
 511                 break;
 512             }
 513         }
 514
 515         let prev = self.cur;
 516         if !specs.is_empty() {
 517             self.cur = self.sets.list.push(LintSet { specs, parent: prev });
 518         }
 519
 520         BuilderPush { prev, changed: prev != self.cur }
 521     }
 522
 523     /// Checks if the lint is gated on a feature that is not enabled.
 524     fn check_gated_lint(&self, lint_id: LintId, span: Span) {
 525         if let Some(feature) = lint_id.lint.feature_gate {
 526             if !self.sess.features_untracked().enabled(feature) {
 527                 feature_err(
 528                     &self.sess.parse_sess,
 529                     feature,
 530                     span,
 531                     &format!("the `{}` lint is unstable", lint_id.lint.name_lower()),
 532                 )
 533                 .emit();
 534             }
 535         }
 536     }
 537
 538     /// Called after `push` when the scope of a set of attributes are exited.
 539     pub fn pop(&mut self, push: BuilderPush) {
 540         self.cur = push.prev;
 541     }
 542
 543     /// Find the lint level for a lint.
 544     pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
 545         self.sets.get_lint_level(lint, self.cur, None, self.sess)
 546     }
 547
 548     /// Used to emit a lint-related diagnostic based on the current state of
 549     /// this lint context.
 550     pub fn struct_lint(
 551         &self,
 552         lint: &'static Lint,
 553         span: Option<MultiSpan>,
 554         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 555     ) {
 556         let (level, src) = self.lint_level(lint);
 557         struct_lint_level(self.sess, lint, level, src, span, decorate)
 558     }
 559
 560     /// Registers the ID provided with the current set of lints stored in
 561     /// this context.
 562     pub fn register_id(&mut self, id: HirId) {
 563         self.id_to_set.insert(id, self.cur);
 564     }
 565
 566     pub fn build_map(self) -> LintLevelMap {
 567         LintLevelMap { sets: self.sets, id_to_set: self.id_to_set }
 568     }
 569 }
 570
 571 pub fn is_known_lint_tool(m_item: Symbol, sess: &Session, attrs: &[ast::Attribute]) -> bool {
 572     if [sym::clippy, sym::rustc, sym::rustdoc].contains(&m_item) {
 573         return true;
 574     }
 575     // Look for registered tools
 576     // NOTE: does no error handling; error handling is done by rustc_resolve.
 577     sess.filter_by_name(attrs, sym::register_tool)
 578         .filter_map(|attr| attr.meta_item_list())
 579         .flatten()
 580         .filter_map(|nested_meta| nested_meta.ident())
 581         .map(|ident| ident.name)
 582         .any(|name| name == m_item)
 583 }
 584
 585 struct LintLevelMapBuilder<'a, 'tcx> {
 586     levels: LintLevelsBuilder<'tcx>,
 587     tcx: TyCtxt<'tcx>,
 588     store: &'a LintStore,
 589 }
 590
 591 impl LintLevelMapBuilder<'_, '_> {
 592     fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
 593     where
 594         F: FnOnce(&mut Self),
 595     {
 596         let is_crate_hir = id == hir::CRATE_HIR_ID;
 597         let attrs = self.tcx.hir().attrs(id);
 598         let push = self.levels.push(attrs, self.store, is_crate_hir);
 599         if push.changed {
 600             self.levels.register_id(id);
 601         }
 602         f(self);
 603         self.levels.pop(push);
 604     }
 605 }
 606
 607 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
 608     type Map = Map<'tcx>;
 609
 610     fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
 611         intravisit::NestedVisitorMap::All(self.tcx.hir())
 612     }
 613
 614     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 615         self.with_lint_attrs(param.hir_id, |builder| {
 616             intravisit::walk_param(builder, param);
 617         });
 618     }
 619
 620     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 621         self.with_lint_attrs(it.hir_id(), |builder| {
 622             intravisit::walk_item(builder, it);
 623         });
 624     }
 625
 626     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 627         self.with_lint_attrs(it.hir_id(), |builder| {
 628             intravisit::walk_foreign_item(builder, it);
 629         })
 630     }
 631
 632     fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
 633         // We will call `with_lint_attrs` when we walk
 634         // the `StmtKind`. The outer statement itself doesn't
 635         // define the lint levels.
 636         intravisit::walk_stmt(self, e);
 637     }
 638
 639     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 640         self.with_lint_attrs(e.hir_id, |builder| {
 641             intravisit::walk_expr(builder, e);
 642         })
 643     }
 644
 645     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
 646         self.with_lint_attrs(s.hir_id, |builder| {
 647             intravisit::walk_field_def(builder, s);
 648         })
 649     }
 650
 651     fn visit_variant(
 652         &mut self,
 653         v: &'tcx hir::Variant<'tcx>,
 654         g: &'tcx hir::Generics<'tcx>,
 655         item_id: hir::HirId,
 656     ) {
 657         self.with_lint_attrs(v.id, |builder| {
 658             intravisit::walk_variant(builder, v, g, item_id);
 659         })
 660     }
 661
 662     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 663         self.with_lint_attrs(l.hir_id, |builder| {
 664             intravisit::walk_local(builder, l);
 665         })
 666     }
 667
 668     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 669         self.with_lint_attrs(a.hir_id, |builder| {
 670             intravisit::walk_arm(builder, a);
 671         })
 672     }
 673
 674     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 675         self.with_lint_attrs(trait_item.hir_id(), |builder| {
 676             intravisit::walk_trait_item(builder, trait_item);
 677         });
 678     }
 679
 680     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 681         self.with_lint_attrs(impl_item.hir_id(), |builder| {
 682             intravisit::walk_impl_item(builder, impl_item);
 683         });
 684     }
 685 }
 686
 687 pub fn provide(providers: &mut Providers) {
 688     providers.lint_levels = lint_levels;
 689 }