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 use std::cmp;
  30
  31 fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
  32     let store = unerased_lint_store(tcx);
  33     let crate_attrs = tcx.hir().attrs(CRATE_HIR_ID);
  34     let levels = LintLevelsBuilder::new(tcx.sess, false, &store, crate_attrs);
  35     let mut builder = LintLevelMapBuilder { levels, tcx, store };
  36     let krate = tcx.hir().krate();
  37
  38     builder.levels.id_to_set.reserve(krate.exported_macros.len() + 1);
  39
  40     let push = builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), &store, true);
  41     builder.levels.register_id(hir::CRATE_HIR_ID);
  42     for macro_def in krate.exported_macros {
  43         builder.levels.register_id(macro_def.hir_id());
  44     }
  45     intravisit::walk_crate(&mut builder, krate);
  46     builder.levels.pop(push);
  47
  48     builder.levels.build_map()
  49 }
  50
  51 pub struct LintLevelsBuilder<'s> {
  52     sess: &'s Session,
  53     sets: LintLevelSets,
  54     id_to_set: FxHashMap<HirId, LintStackIndex>,
  55     cur: LintStackIndex,
  56     warn_about_weird_lints: bool,
  57     store: &'s LintStore,
  58     crate_attrs: &'s [ast::Attribute],
  59 }
  60
  61 pub struct BuilderPush {
  62     prev: LintStackIndex,
  63     pub changed: bool,
  64 }
  65
  66 impl<'s> LintLevelsBuilder<'s> {
  67     pub fn new(
  68         sess: &'s Session,
  69         warn_about_weird_lints: bool,
  70         store: &'s LintStore,
  71         crate_attrs: &'s [ast::Attribute],
  72     ) -> Self {
  73         let mut builder = LintLevelsBuilder {
  74             sess,
  75             sets: LintLevelSets::new(),
  76             cur: COMMAND_LINE,
  77             id_to_set: Default::default(),
  78             warn_about_weird_lints,
  79             store,
  80             crate_attrs,
  81         };
  82         builder.process_command_line(sess, store);
  83         assert_eq!(builder.sets.list.len(), 1);
  84         builder
  85     }
  86
  87     fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
  88         let mut specs = FxHashMap::default();
  89         self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
  90
  91         for &(ref lint_name, level) in &sess.opts.lint_opts {
  92             store.check_lint_name_cmdline(sess, &lint_name, level, self.crate_attrs);
  93             let orig_level = level;
  94
  95             // If the cap is less than this specified level, e.g., if we've got
  96             // `--cap-lints allow` but we've also got `-D foo` then we ignore
  97             // this specification as the lint cap will set it to allow anyway.
  98             let level = cmp::min(level, self.sets.lint_cap);
  99
 100             let lint_flag_val = Symbol::intern(lint_name);
 101
 102             let ids = match store.find_lints(&lint_name) {
 103                 Ok(ids) => ids,
 104                 Err(_) => continue, // errors handled in check_lint_name_cmdline above
 105             };
 106             for id in ids {
 107                 self.check_gated_lint(id, DUMMY_SP);
 108                 let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
 109                 specs.insert(id, (level, src));
 110             }
 111         }
 112
 113         for lint_name in &sess.opts.force_warns {
 114             store.check_lint_name_cmdline(sess, lint_name, Level::ForceWarn, self.crate_attrs);
 115             let lints = store
 116                 .find_lints(lint_name)
 117                 .unwrap_or_else(|_| bug!("A valid lint failed to produce a lint ids"));
 118             for id in lints {
 119                 let src = LintLevelSource::CommandLine(Symbol::intern(lint_name), Level::ForceWarn);
 120                 specs.insert(id, (Level::ForceWarn, src));
 121             }
 122         }
 123
 124         self.cur = self.sets.list.push(LintSet { specs, parent: COMMAND_LINE });
 125     }
 126
 127     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
 128     /// (e.g. if a forbid was already inserted on the same scope), then emits a
 129     /// diagnostic with no change to `specs`.
 130     fn insert_spec(
 131         &mut self,
 132         specs: &mut FxHashMap<LintId, LevelAndSource>,
 133         id: LintId,
 134         (level, src): LevelAndSource,
 135     ) {
 136         let (old_level, old_src) =
 137             self.sets.get_lint_level(id.lint, self.cur, Some(&specs), &self.sess);
 138         // Setting to a non-forbid level is an error if the lint previously had
 139         // a forbid level. Note that this is not necessarily true even with a
 140         // `#[forbid(..)]` attribute present, as that is overriden by `--cap-lints`.
 141         //
 142         // This means that this only errors if we're truly lowering the lint
 143         // level from forbid.
 144         if level != Level::Forbid {
 145             if let Level::Forbid = old_level {
 146                 // Backwards compatibility check:
 147                 //
 148                 // We used to not consider `forbid(lint_group)`
 149                 // as preventing `allow(lint)` for some lint `lint` in
 150                 // `lint_group`. For now, issue a future-compatibility
 151                 // warning for this case.
 152                 let id_name = id.lint.name_lower();
 153                 let fcw_warning = match old_src {
 154                     LintLevelSource::Default => false,
 155                     LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
 156                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
 157                 };
 158                 debug!(
 159                     "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
 160                     fcw_warning, specs, old_src, id_name
 161                 );
 162
 163                 let decorate_diag_builder = |mut diag_builder: DiagnosticBuilder<'_>| {
 164                     diag_builder.span_label(src.span(), "overruled by previous forbid");
 165                     match old_src {
 166                         LintLevelSource::Default => {
 167                             diag_builder.note(&format!(
 168                                 "`forbid` lint level is the default for {}",
 169                                 id.to_string()
 170                             ));
 171                         }
 172                         LintLevelSource::Node(_, forbid_source_span, reason) => {
 173                             diag_builder.span_label(forbid_source_span, "`forbid` level set here");
 174                             if let Some(rationale) = reason {
 175                                 diag_builder.note(&rationale.as_str());
 176                             }
 177                         }
 178                         LintLevelSource::CommandLine(_, _) => {
 179                             diag_builder.note("`forbid` lint level was set on command line");
 180                         }
 181                     }
 182                     diag_builder.emit();
 183                 };
 184                 if !fcw_warning {
 185                     let diag_builder = struct_span_err!(
 186                         self.sess,
 187                         src.span(),
 188                         E0453,
 189                         "{}({}) incompatible with previous forbid",
 190                         level.as_str(),
 191                         src.name(),
 192                     );
 193                     decorate_diag_builder(diag_builder);
 194                 } else {
 195                     self.struct_lint(
 196                         FORBIDDEN_LINT_GROUPS,
 197                         Some(src.span().into()),
 198                         |diag_builder| {
 199                             let diag_builder = diag_builder.build(&format!(
 200                                 "{}({}) incompatible with previous forbid",
 201                                 level.as_str(),
 202                                 src.name(),
 203                             ));
 204                             decorate_diag_builder(diag_builder);
 205                         },
 206                     );
 207                 }
 208
 209                 // Retain the forbid lint level, unless we are
 210                 // issuing a FCW. In the FCW case, we want to
 211                 // respect the new setting.
 212                 if !fcw_warning {
 213                     return;
 214                 }
 215             }
 216         }
 217         if let Level::ForceWarn = old_level {
 218             specs.insert(id, (old_level, old_src));
 219         } else {
 220             specs.insert(id, (level, src));
 221         }
 222     }
 223
 224     /// Pushes a list of AST lint attributes onto this context.
 225     ///
 226     /// This function will return a `BuilderPush` object which should be passed
 227     /// to `pop` when this scope for the attributes provided is exited.
 228     ///
 229     /// This function will perform a number of tasks:
 230     ///
 231     /// * It'll validate all lint-related attributes in `attrs`
 232     /// * It'll mark all lint-related attributes as used
 233     /// * Lint levels will be updated based on the attributes provided
 234     /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
 235     ///   `#[allow]`
 236     ///
 237     /// Don't forget to call `pop`!
 238     pub(crate) fn push(
 239         &mut self,
 240         attrs: &[ast::Attribute],
 241         store: &LintStore,
 242         is_crate_node: bool,
 243     ) -> BuilderPush {
 244         let mut specs = FxHashMap::default();
 245         let sess = self.sess;
 246         let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
 247         for attr in attrs {
 248             let level = match Level::from_symbol(attr.name_or_empty()) {
 249                 None => continue,
 250                 Some(lvl) => lvl,
 251             };
 252
 253             self.sess.mark_attr_used(attr);
 254
 255             let mut metas = unwrap_or!(attr.meta_item_list(), continue);
 256
 257             if metas.is_empty() {
 258                 // FIXME (#55112): issue unused-attributes lint for `#[level()]`
 259                 continue;
 260             }
 261
 262             // Before processing the lint names, look for a reason (RFC 2383)
 263             // at the end.
 264             let mut reason = None;
 265             let tail_li = &metas[metas.len() - 1];
 266             if let Some(item) = tail_li.meta_item() {
 267                 match item.kind {
 268                     ast::MetaItemKind::Word => {} // actual lint names handled later
 269                     ast::MetaItemKind::NameValue(ref name_value) => {
 270                         if item.path == sym::reason {
 271                             // FIXME (#55112): issue unused-attributes lint if we thereby
 272                             // don't have any lint names (`#[level(reason = "foo")]`)
 273                             if let ast::LitKind::Str(rationale, _) = name_value.kind {
 274                                 if !self.sess.features_untracked().lint_reasons {
 275                                     feature_err(
 276                                         &self.sess.parse_sess,
 277                                         sym::lint_reasons,
 278                                         item.span,
 279                                         "lint reasons are experimental",
 280                                     )
 281                                     .emit();
 282                                 }
 283                                 reason = Some(rationale);
 284                             } else {
 285                                 bad_attr(name_value.span)
 286                                     .span_label(name_value.span, "reason must be a string literal")
 287                                     .emit();
 288                             }
 289                             // found reason, reslice meta list to exclude it
 290                             metas.pop().unwrap();
 291                         } else {
 292                             bad_attr(item.span)
 293                                 .span_label(item.span, "bad attribute argument")
 294                                 .emit();
 295                         }
 296                     }
 297                     ast::MetaItemKind::List(_) => {
 298                         bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
 299                     }
 300                 }
 301             }
 302
 303             for li in metas {
 304                 let sp = li.span();
 305                 let mut meta_item = match li {
 306                     ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
 307                     _ => {
 308                         let mut err = bad_attr(sp);
 309                         let mut add_label = true;
 310                         if let Some(item) = li.meta_item() {
 311                             if let ast::MetaItemKind::NameValue(_) = item.kind {
 312                                 if item.path == sym::reason {
 313                                     err.span_label(sp, "reason in lint attribute must come last");
 314                                     add_label = false;
 315                                 }
 316                             }
 317                         }
 318                         if add_label {
 319                             err.span_label(sp, "bad attribute argument");
 320                         }
 321                         err.emit();
 322                         continue;
 323                     }
 324                 };
 325                 let tool_ident = if meta_item.path.segments.len() > 1 {
 326                     Some(meta_item.path.segments.remove(0).ident)
 327                 } else {
 328                     None
 329                 };
 330                 let tool_name = tool_ident.map(|ident| ident.name);
 331                 let name = pprust::path_to_string(&meta_item.path);
 332                 let lint_result = store.check_lint_name(sess, &name, tool_name, self.crate_attrs);
 333                 match &lint_result {
 334                     CheckLintNameResult::Ok(ids) => {
 335                         let src = LintLevelSource::Node(
 336                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 337                             sp,
 338                             reason,
 339                         );
 340                         for &id in *ids {
 341                             self.check_gated_lint(id, attr.span);
 342                             self.insert_spec(&mut specs, id, (level, src));
 343                         }
 344                     }
 345
 346                     CheckLintNameResult::Tool(result) => {
 347                         match *result {
 348                             Ok(ids) => {
 349                                 let complete_name =
 350                                     &format!("{}::{}", tool_ident.unwrap().name, name);
 351                                 let src = LintLevelSource::Node(
 352                                     Symbol::intern(complete_name),
 353                                     sp,
 354                                     reason,
 355                                 );
 356                                 for id in ids {
 357                                     self.insert_spec(&mut specs, *id, (level, src));
 358                                 }
 359                             }
 360                             Err((Some(ids), ref new_lint_name)) => {
 361                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 362                                 let (lvl, src) =
 363                                     self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 364                                 struct_lint_level(
 365                                     self.sess,
 366                                     lint,
 367                                     lvl,
 368                                     src,
 369                                     Some(sp.into()),
 370                                     |lint| {
 371                                         let msg = format!(
 372                                             "lint name `{}` is deprecated \
 373                                              and may not have an effect in the future.",
 374                                             name
 375                                         );
 376                                         lint.build(&msg)
 377                                             .span_suggestion(
 378                                                 sp,
 379                                                 "change it to",
 380                                                 new_lint_name.to_string(),
 381                                                 Applicability::MachineApplicable,
 382                                             )
 383                                             .emit();
 384                                     },
 385                                 );
 386
 387                                 let src = LintLevelSource::Node(
 388                                     Symbol::intern(&new_lint_name),
 389                                     sp,
 390                                     reason,
 391                                 );
 392                                 for id in ids {
 393                                     self.insert_spec(&mut specs, *id, (level, src));
 394                                 }
 395                             }
 396                             Err((None, _)) => {
 397                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 398                                 // exist in the tool or the code was not compiled with the tool and
 399                                 // therefore the lint was never added to the `LintStore`. To detect
 400                                 // this is the responsibility of the lint tool.
 401                             }
 402                         }
 403                     }
 404
 405                     &CheckLintNameResult::NoTool => {
 406                         let mut err = struct_span_err!(
 407                             sess,
 408                             tool_ident.map_or(DUMMY_SP, |ident| ident.span),
 409                             E0710,
 410                             "unknown tool name `{}` found in scoped lint: `{}::{}`",
 411                             tool_name.unwrap(),
 412                             tool_name.unwrap(),
 413                             pprust::path_to_string(&meta_item.path),
 414                         );
 415                         if sess.is_nightly_build() {
 416                             err.help(&format!(
 417                                 "add `#![register_tool({})]` to the crate root",
 418                                 tool_name.unwrap()
 419                             ));
 420                         }
 421                         err.emit();
 422                         continue;
 423                     }
 424
 425                     _ if !self.warn_about_weird_lints => {}
 426
 427                     CheckLintNameResult::Warning(msg, renamed) => {
 428                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 429                         let (renamed_lint_level, src) =
 430                             self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 431                         struct_lint_level(
 432                             self.sess,
 433                             lint,
 434                             renamed_lint_level,
 435                             src,
 436                             Some(sp.into()),
 437                             |lint| {
 438                                 let mut err = lint.build(&msg);
 439                                 if let Some(new_name) = &renamed {
 440                                     err.span_suggestion(
 441                                         sp,
 442                                         "use the new name",
 443                                         new_name.to_string(),
 444                                         Applicability::MachineApplicable,
 445                                     );
 446                                 }
 447                                 err.emit();
 448                             },
 449                         );
 450                     }
 451                     CheckLintNameResult::NoLint(suggestion) => {
 452                         let lint = builtin::UNKNOWN_LINTS;
 453                         let (level, src) =
 454                             self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 455                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 456                             let name = if let Some(tool_ident) = tool_ident {
 457                                 format!("{}::{}", tool_ident.name, name)
 458                             } else {
 459                                 name.to_string()
 460                             };
 461                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 462                             if let Some(suggestion) = suggestion {
 463                                 db.span_suggestion(
 464                                     sp,
 465                                     "did you mean",
 466                                     suggestion.to_string(),
 467                                     Applicability::MachineApplicable,
 468                                 );
 469                             }
 470                             db.emit();
 471                         });
 472                     }
 473                 }
 474                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 475                 // This happens outside of the match because the new lint should be applied even if
 476                 // we don't warn about the name change.
 477                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 478                     // Ignore any errors or warnings that happen because the new name is inaccurate
 479                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 480                     if let CheckLintNameResult::Ok(ids) =
 481                         store.check_lint_name(sess, &new_name, None, self.crate_attrs)
 482                     {
 483                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 484                         for &id in ids {
 485                             self.check_gated_lint(id, attr.span);
 486                             self.insert_spec(&mut specs, id, (level, src));
 487                         }
 488                     } else {
 489                         panic!("renamed lint does not exist: {}", new_name);
 490                     }
 491                 }
 492             }
 493         }
 494
 495         if !is_crate_node {
 496             for (id, &(level, ref src)) in specs.iter() {
 497                 if !id.lint.crate_level_only {
 498                     continue;
 499                 }
 500
 501                 let (lint_attr_name, lint_attr_span) = match *src {
 502                     LintLevelSource::Node(name, span, _) => (name, span),
 503                     _ => continue,
 504                 };
 505
 506                 let lint = builtin::UNUSED_ATTRIBUTES;
 507                 let (lint_level, lint_src) =
 508                     self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 509                 struct_lint_level(
 510                     self.sess,
 511                     lint,
 512                     lint_level,
 513                     lint_src,
 514                     Some(lint_attr_span.into()),
 515                     |lint| {
 516                         let mut db = lint.build(&format!(
 517                             "{}({}) is ignored unless specified at crate level",
 518                             level.as_str(),
 519                             lint_attr_name
 520                         ));
 521                         db.emit();
 522                     },
 523                 );
 524                 // don't set a separate error for every lint in the group
 525                 break;
 526             }
 527         }
 528
 529         let prev = self.cur;
 530         if !specs.is_empty() {
 531             self.cur = self.sets.list.push(LintSet { specs, parent: prev });
 532         }
 533
 534         BuilderPush { prev, changed: prev != self.cur }
 535     }
 536
 537     /// Checks if the lint is gated on a feature that is not enabled.
 538     fn check_gated_lint(&self, lint_id: LintId, span: Span) {
 539         if let Some(feature) = lint_id.lint.feature_gate {
 540             if !self.sess.features_untracked().enabled(feature) {
 541                 feature_err(
 542                     &self.sess.parse_sess,
 543                     feature,
 544                     span,
 545                     &format!("the `{}` lint is unstable", lint_id.lint.name_lower()),
 546                 )
 547                 .emit();
 548             }
 549         }
 550     }
 551
 552     /// Called after `push` when the scope of a set of attributes are exited.
 553     pub fn pop(&mut self, push: BuilderPush) {
 554         self.cur = push.prev;
 555     }
 556
 557     /// Find the lint level for a lint.
 558     pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
 559         self.sets.get_lint_level(lint, self.cur, None, self.sess)
 560     }
 561
 562     /// Used to emit a lint-related diagnostic based on the current state of
 563     /// this lint context.
 564     pub fn struct_lint(
 565         &self,
 566         lint: &'static Lint,
 567         span: Option<MultiSpan>,
 568         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 569     ) {
 570         let (level, src) = self.lint_level(lint);
 571         struct_lint_level(self.sess, lint, level, src, span, decorate)
 572     }
 573
 574     /// Registers the ID provided with the current set of lints stored in
 575     /// this context.
 576     pub fn register_id(&mut self, id: HirId) {
 577         self.id_to_set.insert(id, self.cur);
 578     }
 579
 580     pub fn build_map(self) -> LintLevelMap {
 581         LintLevelMap { sets: self.sets, id_to_set: self.id_to_set }
 582     }
 583 }
 584
 585 pub fn is_known_lint_tool(m_item: Symbol, sess: &Session, attrs: &[ast::Attribute]) -> bool {
 586     if [sym::clippy, sym::rustc, sym::rustdoc].contains(&m_item) {
 587         return true;
 588     }
 589     // Look for registered tools
 590     // NOTE: does no error handling; error handling is done by rustc_resolve.
 591     sess.filter_by_name(attrs, sym::register_tool)
 592         .filter_map(|attr| attr.meta_item_list())
 593         .flat_map(std::convert::identity)
 594         .filter_map(|nested_meta| nested_meta.ident())
 595         .map(|ident| ident.name)
 596         .any(|name| name == m_item)
 597 }
 598
 599 struct LintLevelMapBuilder<'a, 'tcx> {
 600     levels: LintLevelsBuilder<'tcx>,
 601     tcx: TyCtxt<'tcx>,
 602     store: &'a LintStore,
 603 }
 604
 605 impl LintLevelMapBuilder<'_, '_> {
 606     fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
 607     where
 608         F: FnOnce(&mut Self),
 609     {
 610         let is_crate_hir = id == hir::CRATE_HIR_ID;
 611         let attrs = self.tcx.hir().attrs(id);
 612         let push = self.levels.push(attrs, self.store, is_crate_hir);
 613         if push.changed {
 614             self.levels.register_id(id);
 615         }
 616         f(self);
 617         self.levels.pop(push);
 618     }
 619 }
 620
 621 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
 622     type Map = Map<'tcx>;
 623
 624     fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
 625         intravisit::NestedVisitorMap::All(self.tcx.hir())
 626     }
 627
 628     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 629         self.with_lint_attrs(param.hir_id, |builder| {
 630             intravisit::walk_param(builder, param);
 631         });
 632     }
 633
 634     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 635         self.with_lint_attrs(it.hir_id(), |builder| {
 636             intravisit::walk_item(builder, it);
 637         });
 638     }
 639
 640     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 641         self.with_lint_attrs(it.hir_id(), |builder| {
 642             intravisit::walk_foreign_item(builder, it);
 643         })
 644     }
 645
 646     fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
 647         // We will call `with_lint_attrs` when we walk
 648         // the `StmtKind`. The outer statement itself doesn't
 649         // define the lint levels.
 650         intravisit::walk_stmt(self, e);
 651     }
 652
 653     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 654         self.with_lint_attrs(e.hir_id, |builder| {
 655             intravisit::walk_expr(builder, e);
 656         })
 657     }
 658
 659     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
 660         self.with_lint_attrs(s.hir_id, |builder| {
 661             intravisit::walk_field_def(builder, s);
 662         })
 663     }
 664
 665     fn visit_variant(
 666         &mut self,
 667         v: &'tcx hir::Variant<'tcx>,
 668         g: &'tcx hir::Generics<'tcx>,
 669         item_id: hir::HirId,
 670     ) {
 671         self.with_lint_attrs(v.id, |builder| {
 672             intravisit::walk_variant(builder, v, g, item_id);
 673         })
 674     }
 675
 676     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 677         self.with_lint_attrs(l.hir_id, |builder| {
 678             intravisit::walk_local(builder, l);
 679         })
 680     }
 681
 682     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 683         self.with_lint_attrs(a.hir_id, |builder| {
 684             intravisit::walk_arm(builder, a);
 685         })
 686     }
 687
 688     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 689         self.with_lint_attrs(trait_item.hir_id(), |builder| {
 690             intravisit::walk_trait_item(builder, trait_item);
 691         });
 692     }
 693
 694     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 695         self.with_lint_attrs(impl_item.hir_id(), |builder| {
 696             intravisit::walk_impl_item(builder, impl_item);
 697         });
 698     }
 699 }
 700
 701 pub fn provide(providers: &mut Providers) {
 702     providers.lint_levels = lint_levels;
 703 }