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::def_id::{CrateNum, DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
  10 use rustc_hir::{intravisit, HirId};
  11 use rustc_middle::hir::map::Map;
  12 use rustc_middle::lint::LevelAndSource;
  13 use rustc_middle::lint::LintDiagnosticBuilder;
  14 use rustc_middle::lint::{
  15     struct_lint_level, LintLevelMap, LintLevelSets, LintLevelSource, LintSet,
  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 use std::cmp;
  30
  31 fn lint_levels(tcx: TyCtxt<'_>, cnum: CrateNum) -> LintLevelMap {
  32     assert_eq!(cnum, LOCAL_CRATE);
  33     let store = unerased_lint_store(tcx);
  34     let crate_attrs = tcx.get_attrs(DefId { krate: cnum, index: CRATE_DEF_INDEX });
  35     let levels = LintLevelsBuilder::new(tcx.sess, false, &store, crate_attrs);
  36     let mut builder = LintLevelMapBuilder { levels, tcx, store };
  37     let krate = tcx.hir().krate();
  38
  39     builder.levels.id_to_set.reserve(krate.exported_macros.len() + 1);
  40
  41     let push = builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), &store, true);
  42     builder.levels.register_id(hir::CRATE_HIR_ID);
  43     for macro_def in krate.exported_macros {
  44         builder.levels.register_id(macro_def.hir_id());
  45     }
  46     intravisit::walk_crate(&mut builder, krate);
  47     builder.levels.pop(push);
  48
  49     builder.levels.build_map()
  50 }
  51
  52 pub struct LintLevelsBuilder<'s> {
  53     sess: &'s Session,
  54     sets: LintLevelSets,
  55     id_to_set: FxHashMap<HirId, u32>,
  56     cur: u32,
  57     warn_about_weird_lints: bool,
  58     store: &'s LintStore,
  59     crate_attrs: &'s [ast::Attribute],
  60 }
  61
  62 pub struct BuilderPush {
  63     prev: u32,
  64     pub changed: bool,
  65 }
  66
  67 impl<'s> LintLevelsBuilder<'s> {
  68     pub fn new(
  69         sess: &'s Session,
  70         warn_about_weird_lints: bool,
  71         store: &'s LintStore,
  72         crate_attrs: &'s [ast::Attribute],
  73     ) -> Self {
  74         let mut builder = LintLevelsBuilder {
  75             sess,
  76             sets: LintLevelSets::new(),
  77             cur: 0,
  78             id_to_set: Default::default(),
  79             warn_about_weird_lints,
  80             store,
  81             crate_attrs,
  82         };
  83         builder.process_command_line(sess, store);
  84         assert_eq!(builder.sets.list.len(), 1);
  85         builder
  86     }
  87
  88     fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
  89         let mut specs = FxHashMap::default();
  90         self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
  91
  92         for &(ref lint_name, level) in &sess.opts.lint_opts {
  93             store.check_lint_name_cmdline(sess, &lint_name, level);
  94             let orig_level = level;
  95
  96             // If the cap is less than this specified level, e.g., if we've got
  97             // `--cap-lints allow` but we've also got `-D foo` then we ignore
  98             // this specification as the lint cap will set it to allow anyway.
  99             let level = cmp::min(level, self.sets.lint_cap);
 100
 101             let lint_flag_val = Symbol::intern(lint_name);
 102
 103             let ids = match store.find_lints(&lint_name) {
 104                 Ok(ids) => ids,
 105                 Err(_) => continue, // errors handled in check_lint_name_cmdline above
 106             };
 107             for id in ids {
 108                 self.check_gated_lint(id, DUMMY_SP);
 109                 let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
 110                 specs.insert(id, (level, src));
 111             }
 112         }
 113
 114         self.sets.list.push(LintSet::CommandLine { specs });
 115     }
 116
 117     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
 118     /// (e.g. if a forbid was already inserted on the same scope), then emits a
 119     /// diagnostic with no change to `specs`.
 120     fn insert_spec(
 121         &mut self,
 122         specs: &mut FxHashMap<LintId, LevelAndSource>,
 123         id: LintId,
 124         (level, src): LevelAndSource,
 125     ) {
 126         // Setting to a non-forbid level is an error if the lint previously had
 127         // a forbid level. Note that this is not necessarily true even with a
 128         // `#[forbid(..)]` attribute present, as that is overriden by `--cap-lints`.
 129         //
 130         // This means that this only errors if we're truly lowering the lint
 131         // level from forbid.
 132         if level != Level::Forbid {
 133             if let (Level::Forbid, old_src) =
 134                 self.sets.get_lint_level(id.lint, self.cur, Some(&specs), &self.sess)
 135             {
 136                 // Backwards compatibility check:
 137                 //
 138                 // We used to not consider `forbid(lint_group)`
 139                 // as preventing `allow(lint)` for some lint `lint` in
 140                 // `lint_group`. For now, issue a future-compatibility
 141                 // warning for this case.
 142                 let id_name = id.lint.name_lower();
 143                 let fcw_warning = match old_src {
 144                     LintLevelSource::Default => false,
 145                     LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
 146                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
 147                 };
 148                 debug!(
 149                     "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
 150                     fcw_warning, specs, old_src, id_name
 151                 );
 152
 153                 let decorate_diag_builder = |mut diag_builder: DiagnosticBuilder<'_>| {
 154                     diag_builder.span_label(src.span(), "overruled by previous forbid");
 155                     match old_src {
 156                         LintLevelSource::Default => {
 157                             diag_builder.note(&format!(
 158                                 "`forbid` lint level is the default for {}",
 159                                 id.to_string()
 160                             ));
 161                         }
 162                         LintLevelSource::Node(_, forbid_source_span, reason) => {
 163                             diag_builder.span_label(forbid_source_span, "`forbid` level set here");
 164                             if let Some(rationale) = reason {
 165                                 diag_builder.note(&rationale.as_str());
 166                             }
 167                         }
 168                         LintLevelSource::CommandLine(_, _) => {
 169                             diag_builder.note("`forbid` lint level was set on command line");
 170                         }
 171                     }
 172                     diag_builder.emit();
 173                 };
 174                 if !fcw_warning {
 175                     let diag_builder = struct_span_err!(
 176                         self.sess,
 177                         src.span(),
 178                         E0453,
 179                         "{}({}) incompatible with previous forbid",
 180                         level.as_str(),
 181                         src.name(),
 182                     );
 183                     decorate_diag_builder(diag_builder);
 184                 } else {
 185                     self.struct_lint(
 186                         FORBIDDEN_LINT_GROUPS,
 187                         Some(src.span().into()),
 188                         |diag_builder| {
 189                             let diag_builder = diag_builder.build(&format!(
 190                                 "{}({}) incompatible with previous forbid",
 191                                 level.as_str(),
 192                                 src.name(),
 193                             ));
 194                             decorate_diag_builder(diag_builder);
 195                         },
 196                     );
 197                 }
 198
 199                 // Retain the forbid lint level, unless we are
 200                 // issuing a FCW. In the FCW case, we want to
 201                 // respect the new setting.
 202                 if !fcw_warning {
 203                     return;
 204                 }
 205             }
 206         }
 207         specs.insert(id, (level, src));
 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_name = if meta_item.path.segments.len() > 1 {
 312                     let tool_ident = meta_item.path.segments[0].ident;
 313                     if !is_known_lint_tool(tool_ident.name, sess, &self.crate_attrs) {
 314                         let mut err = struct_span_err!(
 315                             sess,
 316                             tool_ident.span,
 317                             E0710,
 318                             "unknown tool name `{}` found in scoped lint: `{}`",
 319                             tool_ident.name,
 320                             pprust::path_to_string(&meta_item.path),
 321                         );
 322                         if sess.is_nightly_build() {
 323                             err.help(&format!(
 324                                 "add `#![register_tool({})]` to the crate root",
 325                                 tool_ident.name
 326                             ));
 327                         }
 328                         err.emit();
 329                         continue;
 330                     }
 331
 332                     Some(meta_item.path.segments.remove(0).ident.name)
 333                 } else {
 334                     None
 335                 };
 336                 let name = pprust::path_to_string(&meta_item.path);
 337                 let lint_result = store.check_lint_name(&name, tool_name);
 338                 match &lint_result {
 339                     CheckLintNameResult::Ok(ids) => {
 340                         let src = LintLevelSource::Node(
 341                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 342                             sp,
 343                             reason,
 344                         );
 345                         for &id in *ids {
 346                             self.check_gated_lint(id, attr.span);
 347                             self.insert_spec(&mut specs, id, (level, src));
 348                         }
 349                     }
 350
 351                     CheckLintNameResult::Tool(result) => {
 352                         match *result {
 353                             Ok(ids) => {
 354                                 let complete_name = &format!("{}::{}", tool_name.unwrap(), name);
 355                                 let src = LintLevelSource::Node(
 356                                     Symbol::intern(complete_name),
 357                                     sp,
 358                                     reason,
 359                                 );
 360                                 for id in ids {
 361                                     self.insert_spec(&mut specs, *id, (level, src));
 362                                 }
 363                             }
 364                             Err((Some(ids), ref new_lint_name)) => {
 365                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 366                                 let (lvl, src) =
 367                                     self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 368                                 struct_lint_level(
 369                                     self.sess,
 370                                     lint,
 371                                     lvl,
 372                                     src,
 373                                     Some(sp.into()),
 374                                     |lint| {
 375                                         let msg = format!(
 376                                             "lint name `{}` is deprecated \
 377                                              and may not have an effect in the future.",
 378                                             name
 379                                         );
 380                                         lint.build(&msg)
 381                                             .span_suggestion(
 382                                                 sp,
 383                                                 "change it to",
 384                                                 new_lint_name.to_string(),
 385                                                 Applicability::MachineApplicable,
 386                                             )
 387                                             .emit();
 388                                     },
 389                                 );
 390
 391                                 let src = LintLevelSource::Node(
 392                                     Symbol::intern(&new_lint_name),
 393                                     sp,
 394                                     reason,
 395                                 );
 396                                 for id in ids {
 397                                     self.insert_spec(&mut specs, *id, (level, src));
 398                                 }
 399                             }
 400                             Err((None, _)) => {
 401                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 402                                 // exist in the tool or the code was not compiled with the tool and
 403                                 // therefore the lint was never added to the `LintStore`. To detect
 404                                 // this is the responsibility of the lint tool.
 405                             }
 406                         }
 407                     }
 408
 409                     _ if !self.warn_about_weird_lints => {}
 410
 411                     CheckLintNameResult::Warning(msg, renamed) => {
 412                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 413                         let (renamed_lint_level, src) =
 414                             self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 415                         struct_lint_level(
 416                             self.sess,
 417                             lint,
 418                             renamed_lint_level,
 419                             src,
 420                             Some(sp.into()),
 421                             |lint| {
 422                                 let mut err = lint.build(&msg);
 423                                 if let Some(new_name) = &renamed {
 424                                     err.span_suggestion(
 425                                         sp,
 426                                         "use the new name",
 427                                         new_name.to_string(),
 428                                         Applicability::MachineApplicable,
 429                                     );
 430                                 }
 431                                 err.emit();
 432                             },
 433                         );
 434                     }
 435                     CheckLintNameResult::NoLint(suggestion) => {
 436                         let lint = builtin::UNKNOWN_LINTS;
 437                         let (level, src) =
 438                             self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 439                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 440                             let name = if let Some(tool_name) = tool_name {
 441                                 format!("{}::{}", tool_name, name)
 442                             } else {
 443                                 name.to_string()
 444                             };
 445                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 446                             if let Some(suggestion) = suggestion {
 447                                 db.span_suggestion(
 448                                     sp,
 449                                     "did you mean",
 450                                     suggestion.to_string(),
 451                                     Applicability::MachineApplicable,
 452                                 );
 453                             }
 454                             db.emit();
 455                         });
 456                     }
 457                 }
 458                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 459                 // This happens outside of the match because the new lint should be applied even if
 460                 // we don't warn about the name change.
 461                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 462                     // Ignore any errors or warnings that happen because the new name is inaccurate
 463                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 464                     if let CheckLintNameResult::Ok(ids) = store.check_lint_name(&new_name, None) {
 465                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 466                         for &id in ids {
 467                             self.check_gated_lint(id, attr.span);
 468                             self.insert_spec(&mut specs, id, (level, src));
 469                         }
 470                     } else {
 471                         panic!("renamed lint does not exist: {}", new_name);
 472                     }
 473                 }
 474             }
 475         }
 476
 477         if !is_crate_node {
 478             for (id, &(level, ref src)) in specs.iter() {
 479                 if !id.lint.crate_level_only {
 480                     continue;
 481                 }
 482
 483                 let (lint_attr_name, lint_attr_span) = match *src {
 484                     LintLevelSource::Node(name, span, _) => (name, span),
 485                     _ => continue,
 486                 };
 487
 488                 let lint = builtin::UNUSED_ATTRIBUTES;
 489                 let (lint_level, lint_src) =
 490                     self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 491                 struct_lint_level(
 492                     self.sess,
 493                     lint,
 494                     lint_level,
 495                     lint_src,
 496                     Some(lint_attr_span.into()),
 497                     |lint| {
 498                         let mut db = lint.build(&format!(
 499                             "{}({}) is ignored unless specified at crate level",
 500                             level.as_str(),
 501                             lint_attr_name
 502                         ));
 503                         db.emit();
 504                     },
 505                 );
 506                 // don't set a separate error for every lint in the group
 507                 break;
 508             }
 509         }
 510
 511         let prev = self.cur;
 512         if !specs.is_empty() {
 513             self.cur = self.sets.list.len() as u32;
 514             self.sets.list.push(LintSet::Node { 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 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         .flat_map(std::convert::identity)
 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 }