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 level = match Level::from_symbol(attr.name_or_empty()) {
 231                 None => continue,
 232                 Some(lvl) => lvl,
 233             };
 234
 235             let mut metas = match attr.meta_item_list() {
 236                 Some(x) => x,
 237                 None => continue,
 238             };
 239
 240             if metas.is_empty() {
 241                 // FIXME (#55112): issue unused-attributes lint for `#[level()]`
 242                 continue;
 243             }
 244
 245             // Before processing the lint names, look for a reason (RFC 2383)
 246             // at the end.
 247             let mut reason = None;
 248             let tail_li = &metas[metas.len() - 1];
 249             if let Some(item) = tail_li.meta_item() {
 250                 match item.kind {
 251                     ast::MetaItemKind::Word => {} // actual lint names handled later
 252                     ast::MetaItemKind::NameValue(ref name_value) => {
 253                         if item.path == sym::reason {
 254                             // FIXME (#55112): issue unused-attributes lint if we thereby
 255                             // don't have any lint names (`#[level(reason = "foo")]`)
 256                             if let ast::LitKind::Str(rationale, _) = name_value.kind {
 257                                 if !self.sess.features_untracked().lint_reasons {
 258                                     feature_err(
 259                                         &self.sess.parse_sess,
 260                                         sym::lint_reasons,
 261                                         item.span,
 262                                         "lint reasons are experimental",
 263                                     )
 264                                     .emit();
 265                                 }
 266                                 reason = Some(rationale);
 267                             } else {
 268                                 bad_attr(name_value.span)
 269                                     .span_label(name_value.span, "reason must be a string literal")
 270                                     .emit();
 271                             }
 272                             // found reason, reslice meta list to exclude it
 273                             metas.pop().unwrap();
 274                         } else {
 275                             bad_attr(item.span)
 276                                 .span_label(item.span, "bad attribute argument")
 277                                 .emit();
 278                         }
 279                     }
 280                     ast::MetaItemKind::List(_) => {
 281                         bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
 282                     }
 283                 }
 284             }
 285
 286             for li in metas {
 287                 let sp = li.span();
 288                 let mut meta_item = match li {
 289                     ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
 290                     _ => {
 291                         let mut err = bad_attr(sp);
 292                         let mut add_label = true;
 293                         if let Some(item) = li.meta_item() {
 294                             if let ast::MetaItemKind::NameValue(_) = item.kind {
 295                                 if item.path == sym::reason {
 296                                     err.span_label(sp, "reason in lint attribute must come last");
 297                                     add_label = false;
 298                                 }
 299                             }
 300                         }
 301                         if add_label {
 302                             err.span_label(sp, "bad attribute argument");
 303                         }
 304                         err.emit();
 305                         continue;
 306                     }
 307                 };
 308                 let tool_ident = if meta_item.path.segments.len() > 1 {
 309                     Some(meta_item.path.segments.remove(0).ident)
 310                 } else {
 311                     None
 312                 };
 313                 let tool_name = tool_ident.map(|ident| ident.name);
 314                 let name = pprust::path_to_string(&meta_item.path);
 315                 let lint_result = store.check_lint_name(sess, &name, tool_name, self.crate_attrs);
 316                 match &lint_result {
 317                     CheckLintNameResult::Ok(ids) => {
 318                         let src = LintLevelSource::Node(
 319                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 320                             sp,
 321                             reason,
 322                         );
 323                         for &id in *ids {
 324                             self.check_gated_lint(id, attr.span);
 325                             self.insert_spec(&mut specs, id, (level, src));
 326                         }
 327                     }
 328
 329                     CheckLintNameResult::Tool(result) => {
 330                         match *result {
 331                             Ok(ids) => {
 332                                 let complete_name =
 333                                     &format!("{}::{}", tool_ident.unwrap().name, name);
 334                                 let src = LintLevelSource::Node(
 335                                     Symbol::intern(complete_name),
 336                                     sp,
 337                                     reason,
 338                                 );
 339                                 for id in ids {
 340                                     self.insert_spec(&mut specs, *id, (level, src));
 341                                 }
 342                             }
 343                             Err((Some(ids), ref new_lint_name)) => {
 344                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 345                                 let (lvl, src) =
 346                                     self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 347                                 struct_lint_level(
 348                                     self.sess,
 349                                     lint,
 350                                     lvl,
 351                                     src,
 352                                     Some(sp.into()),
 353                                     |lint| {
 354                                         let msg = format!(
 355                                             "lint name `{}` is deprecated \
 356                                              and may not have an effect in the future.",
 357                                             name
 358                                         );
 359                                         lint.build(&msg)
 360                                             .span_suggestion(
 361                                                 sp,
 362                                                 "change it to",
 363                                                 new_lint_name.to_string(),
 364                                                 Applicability::MachineApplicable,
 365                                             )
 366                                             .emit();
 367                                     },
 368                                 );
 369
 370                                 let src = LintLevelSource::Node(
 371                                     Symbol::intern(&new_lint_name),
 372                                     sp,
 373                                     reason,
 374                                 );
 375                                 for id in ids {
 376                                     self.insert_spec(&mut specs, *id, (level, src));
 377                                 }
 378                             }
 379                             Err((None, _)) => {
 380                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 381                                 // exist in the tool or the code was not compiled with the tool and
 382                                 // therefore the lint was never added to the `LintStore`. To detect
 383                                 // this is the responsibility of the lint tool.
 384                             }
 385                         }
 386                     }
 387
 388                     &CheckLintNameResult::NoTool => {
 389                         let mut err = struct_span_err!(
 390                             sess,
 391                             tool_ident.map_or(DUMMY_SP, |ident| ident.span),
 392                             E0710,
 393                             "unknown tool name `{}` found in scoped lint: `{}::{}`",
 394                             tool_name.unwrap(),
 395                             tool_name.unwrap(),
 396                             pprust::path_to_string(&meta_item.path),
 397                         );
 398                         if sess.is_nightly_build() {
 399                             err.help(&format!(
 400                                 "add `#![register_tool({})]` to the crate root",
 401                                 tool_name.unwrap()
 402                             ));
 403                         }
 404                         err.emit();
 405                         continue;
 406                     }
 407
 408                     _ if !self.warn_about_weird_lints => {}
 409
 410                     CheckLintNameResult::Warning(msg, renamed) => {
 411                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 412                         let (renamed_lint_level, src) =
 413                             self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 414                         struct_lint_level(
 415                             self.sess,
 416                             lint,
 417                             renamed_lint_level,
 418                             src,
 419                             Some(sp.into()),
 420                             |lint| {
 421                                 let mut err = lint.build(&msg);
 422                                 if let Some(new_name) = &renamed {
 423                                     err.span_suggestion(
 424                                         sp,
 425                                         "use the new name",
 426                                         new_name.to_string(),
 427                                         Applicability::MachineApplicable,
 428                                     );
 429                                 }
 430                                 err.emit();
 431                             },
 432                         );
 433                     }
 434                     CheckLintNameResult::NoLint(suggestion) => {
 435                         let lint = builtin::UNKNOWN_LINTS;
 436                         let (level, src) =
 437                             self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 438                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 439                             let name = if let Some(tool_ident) = tool_ident {
 440                                 format!("{}::{}", tool_ident.name, name)
 441                             } else {
 442                                 name.to_string()
 443                             };
 444                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 445                             if let Some(suggestion) = suggestion {
 446                                 db.span_suggestion(
 447                                     sp,
 448                                     "did you mean",
 449                                     suggestion.to_string(),
 450                                     Applicability::MachineApplicable,
 451                                 );
 452                             }
 453                             db.emit();
 454                         });
 455                     }
 456                 }
 457                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 458                 // This happens outside of the match because the new lint should be applied even if
 459                 // we don't warn about the name change.
 460                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 461                     // Ignore any errors or warnings that happen because the new name is inaccurate
 462                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 463                     if let CheckLintNameResult::Ok(ids) =
 464                         store.check_lint_name(sess, &new_name, None, self.crate_attrs)
 465                     {
 466                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 467                         for &id in ids {
 468                             self.check_gated_lint(id, attr.span);
 469                             self.insert_spec(&mut specs, id, (level, src));
 470                         }
 471                     } else {
 472                         panic!("renamed lint does not exist: {}", new_name);
 473                     }
 474                 }
 475             }
 476         }
 477
 478         if !is_crate_node {
 479             for (id, &(level, ref src)) in specs.iter() {
 480                 if !id.lint.crate_level_only {
 481                     continue;
 482                 }
 483
 484                 let (lint_attr_name, lint_attr_span) = match *src {
 485                     LintLevelSource::Node(name, span, _) => (name, span),
 486                     _ => continue,
 487                 };
 488
 489                 let lint = builtin::UNUSED_ATTRIBUTES;
 490                 let (lint_level, lint_src) =
 491                     self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 492                 struct_lint_level(
 493                     self.sess,
 494                     lint,
 495                     lint_level,
 496                     lint_src,
 497                     Some(lint_attr_span.into()),
 498                     |lint| {
 499                         let mut db = lint.build(&format!(
 500                             "{}({}) is ignored unless specified at crate level",
 501                             level.as_str(),
 502                             lint_attr_name
 503                         ));
 504                         db.emit();
 505                     },
 506                 );
 507                 // don't set a separate error for every lint in the group
 508                 break;
 509             }
 510         }
 511
 512         let prev = self.cur;
 513         if !specs.is_empty() {
 514             self.cur = self.sets.list.push(LintSet { specs, parent: prev });
 515         }
 516
 517         BuilderPush { prev, changed: prev != self.cur }
 518     }
 519
 520     /// Checks if the lint is gated on a feature that is not enabled.
 521     fn check_gated_lint(&self, lint_id: LintId, span: Span) {
 522         if let Some(feature) = lint_id.lint.feature_gate {
 523             if !self.sess.features_untracked().enabled(feature) {
 524                 feature_err(
 525                     &self.sess.parse_sess,
 526                     feature,
 527                     span,
 528                     &format!("the `{}` lint is unstable", lint_id.lint.name_lower()),
 529                 )
 530                 .emit();
 531             }
 532         }
 533     }
 534
 535     /// Called after `push` when the scope of a set of attributes are exited.
 536     pub fn pop(&mut self, push: BuilderPush) {
 537         self.cur = push.prev;
 538     }
 539
 540     /// Find the lint level for a lint.
 541     pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
 542         self.sets.get_lint_level(lint, self.cur, None, self.sess)
 543     }
 544
 545     /// Used to emit a lint-related diagnostic based on the current state of
 546     /// this lint context.
 547     pub fn struct_lint(
 548         &self,
 549         lint: &'static Lint,
 550         span: Option<MultiSpan>,
 551         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 552     ) {
 553         let (level, src) = self.lint_level(lint);
 554         struct_lint_level(self.sess, lint, level, src, span, decorate)
 555     }
 556
 557     /// Registers the ID provided with the current set of lints stored in
 558     /// this context.
 559     pub fn register_id(&mut self, id: HirId) {
 560         self.id_to_set.insert(id, self.cur);
 561     }
 562
 563     pub fn build_map(self) -> LintLevelMap {
 564         LintLevelMap { sets: self.sets, id_to_set: self.id_to_set }
 565     }
 566 }
 567
 568 pub fn is_known_lint_tool(m_item: Symbol, sess: &Session, attrs: &[ast::Attribute]) -> bool {
 569     if [sym::clippy, sym::rustc, sym::rustdoc].contains(&m_item) {
 570         return true;
 571     }
 572     // Look for registered tools
 573     // NOTE: does no error handling; error handling is done by rustc_resolve.
 574     sess.filter_by_name(attrs, sym::register_tool)
 575         .filter_map(|attr| attr.meta_item_list())
 576         .flatten()
 577         .filter_map(|nested_meta| nested_meta.ident())
 578         .map(|ident| ident.name)
 579         .any(|name| name == m_item)
 580 }
 581
 582 struct LintLevelMapBuilder<'a, 'tcx> {
 583     levels: LintLevelsBuilder<'tcx>,
 584     tcx: TyCtxt<'tcx>,
 585     store: &'a LintStore,
 586 }
 587
 588 impl LintLevelMapBuilder<'_, '_> {
 589     fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
 590     where
 591         F: FnOnce(&mut Self),
 592     {
 593         let is_crate_hir = id == hir::CRATE_HIR_ID;
 594         let attrs = self.tcx.hir().attrs(id);
 595         let push = self.levels.push(attrs, self.store, is_crate_hir);
 596         if push.changed {
 597             self.levels.register_id(id);
 598         }
 599         f(self);
 600         self.levels.pop(push);
 601     }
 602 }
 603
 604 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
 605     type Map = Map<'tcx>;
 606
 607     fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
 608         intravisit::NestedVisitorMap::All(self.tcx.hir())
 609     }
 610
 611     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 612         self.with_lint_attrs(param.hir_id, |builder| {
 613             intravisit::walk_param(builder, param);
 614         });
 615     }
 616
 617     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 618         self.with_lint_attrs(it.hir_id(), |builder| {
 619             intravisit::walk_item(builder, it);
 620         });
 621     }
 622
 623     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 624         self.with_lint_attrs(it.hir_id(), |builder| {
 625             intravisit::walk_foreign_item(builder, it);
 626         })
 627     }
 628
 629     fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
 630         // We will call `with_lint_attrs` when we walk
 631         // the `StmtKind`. The outer statement itself doesn't
 632         // define the lint levels.
 633         intravisit::walk_stmt(self, e);
 634     }
 635
 636     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 637         self.with_lint_attrs(e.hir_id, |builder| {
 638             intravisit::walk_expr(builder, e);
 639         })
 640     }
 641
 642     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
 643         self.with_lint_attrs(s.hir_id, |builder| {
 644             intravisit::walk_field_def(builder, s);
 645         })
 646     }
 647
 648     fn visit_variant(
 649         &mut self,
 650         v: &'tcx hir::Variant<'tcx>,
 651         g: &'tcx hir::Generics<'tcx>,
 652         item_id: hir::HirId,
 653     ) {
 654         self.with_lint_attrs(v.id, |builder| {
 655             intravisit::walk_variant(builder, v, g, item_id);
 656         })
 657     }
 658
 659     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 660         self.with_lint_attrs(l.hir_id, |builder| {
 661             intravisit::walk_local(builder, l);
 662         })
 663     }
 664
 665     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 666         self.with_lint_attrs(a.hir_id, |builder| {
 667             intravisit::walk_arm(builder, a);
 668         })
 669     }
 670
 671     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 672         self.with_lint_attrs(trait_item.hir_id(), |builder| {
 673             intravisit::walk_trait_item(builder, trait_item);
 674         });
 675     }
 676
 677     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 678         self.with_lint_attrs(impl_item.hir_id(), |builder| {
 679             intravisit::walk_impl_item(builder, impl_item);
 680         });
 681     }
 682 }
 683
 684 pub fn provide(providers: &mut Providers) {
 685     providers.lint_levels = lint_levels;
 686 }