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, Diagnostic};
   7 use rustc_hir as hir;
   8 use rustc_hir::{intravisit, HirId};
   9 use rustc_middle::hir::nested_filter;
  10 use rustc_middle::lint::{
  11     struct_lint_level, LevelAndSource, LintDiagnosticBuilder, LintExpectation, LintLevelMap,
  12     LintLevelSets, LintLevelSource, LintSet, LintStackIndex, COMMAND_LINE,
  13 };
  14 use rustc_middle::ty::query::Providers;
  15 use rustc_middle::ty::{RegisteredTools, TyCtxt};
  16 use rustc_session::lint::{
  17     builtin::{self, FORBIDDEN_LINT_GROUPS},
  18     Level, Lint, LintExpectationId, LintId,
  19 };
  20 use rustc_session::parse::feature_err;
  21 use rustc_session::Session;
  22 use rustc_span::symbol::{sym, Symbol};
  23 use rustc_span::{source_map::MultiSpan, Span, DUMMY_SP};
  24 use tracing::debug;
  25
  26 fn lint_levels(tcx: TyCtxt<'_>, (): ()) -> LintLevelMap {
  27     let store = unerased_lint_store(tcx);
  28     let levels =
  29         LintLevelsBuilder::new(tcx.sess, false, &store, &tcx.resolutions(()).registered_tools);
  30     let mut builder = LintLevelMapBuilder { levels, tcx };
  31     let krate = tcx.hir().krate();
  32
  33     builder.levels.id_to_set.reserve(krate.owners.len() + 1);
  34
  35     let push =
  36         builder.levels.push(tcx.hir().attrs(hir::CRATE_HIR_ID), true, Some(hir::CRATE_HIR_ID));
  37
  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.update_unstable_expectation_ids();
  43     builder.levels.build_map()
  44 }
  45
  46 pub struct LintLevelsBuilder<'s> {
  47     sess: &'s Session,
  48     lint_expectations: Vec<(LintExpectationId, LintExpectation)>,
  49     /// Each expectation has a stable and an unstable identifier. This map
  50     /// is used to map from unstable to stable [`LintExpectationId`]s.
  51     expectation_id_map: FxHashMap<LintExpectationId, LintExpectationId>,
  52     sets: LintLevelSets,
  53     id_to_set: FxHashMap<HirId, LintStackIndex>,
  54     cur: LintStackIndex,
  55     warn_about_weird_lints: bool,
  56     store: &'s LintStore,
  57     registered_tools: &'s RegisteredTools,
  58 }
  59
  60 pub struct BuilderPush {
  61     prev: LintStackIndex,
  62     pub changed: bool,
  63 }
  64
  65 impl<'s> LintLevelsBuilder<'s> {
  66     pub fn new(
  67         sess: &'s Session,
  68         warn_about_weird_lints: bool,
  69         store: &'s LintStore,
  70         registered_tools: &'s RegisteredTools,
  71     ) -> Self {
  72         let mut builder = LintLevelsBuilder {
  73             sess,
  74             lint_expectations: Default::default(),
  75             expectation_id_map: Default::default(),
  76             sets: LintLevelSets::new(),
  77             cur: COMMAND_LINE,
  78             id_to_set: Default::default(),
  79             warn_about_weird_lints,
  80             store,
  81             registered_tools,
  82         };
  83         builder.process_command_line(sess, store);
  84         assert_eq!(builder.sets.list.len(), 1);
  85         builder
  86     }
  87
  88     pub(crate) fn sess(&self) -> &Session {
  89         self.sess
  90     }
  91
  92     pub(crate) fn lint_store(&self) -> &LintStore {
  93         self.store
  94     }
  95
  96     fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
  97         let mut specs = FxHashMap::default();
  98         self.sets.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
  99
 100         for &(ref lint_name, level) in &sess.opts.lint_opts {
 101             store.check_lint_name_cmdline(sess, &lint_name, level, self.registered_tools);
 102             let orig_level = level;
 103             let lint_flag_val = Symbol::intern(lint_name);
 104
 105             let Ok(ids) = store.find_lints(&lint_name) else {
 106                 // errors handled in check_lint_name_cmdline above
 107                 continue
 108             };
 109             for id in ids {
 110                 // ForceWarn and Forbid cannot be overriden
 111                 if let Some((Level::ForceWarn | Level::Forbid, _)) = specs.get(&id) {
 112                     continue;
 113                 }
 114
 115                 self.check_gated_lint(id, DUMMY_SP);
 116                 let src = LintLevelSource::CommandLine(lint_flag_val, orig_level);
 117                 specs.insert(id, (level, src));
 118             }
 119         }
 120
 121         self.cur = self.sets.list.push(LintSet { specs, parent: COMMAND_LINE });
 122     }
 123
 124     /// Attempts to insert the `id` to `level_src` map entry. If unsuccessful
 125     /// (e.g. if a forbid was already inserted on the same scope), then emits a
 126     /// diagnostic with no change to `specs`.
 127     fn insert_spec(
 128         &mut self,
 129         specs: &mut FxHashMap<LintId, LevelAndSource>,
 130         id: LintId,
 131         (level, src): LevelAndSource,
 132     ) {
 133         let (old_level, old_src) =
 134             self.sets.get_lint_level(id.lint, self.cur, Some(&specs), &self.sess);
 135         // Setting to a non-forbid level is an error if the lint previously had
 136         // a forbid level. Note that this is not necessarily true even with a
 137         // `#[forbid(..)]` attribute present, as that is overriden by `--cap-lints`.
 138         //
 139         // This means that this only errors if we're truly lowering the lint
 140         // level from forbid.
 141         if level != Level::Forbid {
 142             if let Level::Forbid = old_level {
 143                 // Backwards compatibility check:
 144                 //
 145                 // We used to not consider `forbid(lint_group)`
 146                 // as preventing `allow(lint)` for some lint `lint` in
 147                 // `lint_group`. For now, issue a future-compatibility
 148                 // warning for this case.
 149                 let id_name = id.lint.name_lower();
 150                 let fcw_warning = match old_src {
 151                     LintLevelSource::Default => false,
 152                     LintLevelSource::Node(symbol, _, _) => self.store.is_lint_group(symbol),
 153                     LintLevelSource::CommandLine(symbol, _) => self.store.is_lint_group(symbol),
 154                 };
 155                 debug!(
 156                     "fcw_warning={:?}, specs.get(&id) = {:?}, old_src={:?}, id_name={:?}",
 157                     fcw_warning, specs, old_src, id_name
 158                 );
 159
 160                 let decorate_diag = |diag: &mut Diagnostic| {
 161                     diag.span_label(src.span(), "overruled by previous forbid");
 162                     match old_src {
 163                         LintLevelSource::Default => {
 164                             diag.note(&format!(
 165                                 "`forbid` lint level is the default for {}",
 166                                 id.to_string()
 167                             ));
 168                         }
 169                         LintLevelSource::Node(_, forbid_source_span, reason) => {
 170                             diag.span_label(forbid_source_span, "`forbid` level set here");
 171                             if let Some(rationale) = reason {
 172                                 diag.note(rationale.as_str());
 173                             }
 174                         }
 175                         LintLevelSource::CommandLine(_, _) => {
 176                             diag.note("`forbid` lint level was set on command line");
 177                         }
 178                     }
 179                 };
 180                 if !fcw_warning {
 181                     let mut diag_builder = struct_span_err!(
 182                         self.sess,
 183                         src.span(),
 184                         E0453,
 185                         "{}({}) incompatible with previous forbid",
 186                         level.as_str(),
 187                         src.name(),
 188                     );
 189                     decorate_diag(&mut diag_builder);
 190                     diag_builder.emit();
 191                 } else {
 192                     self.struct_lint(
 193                         FORBIDDEN_LINT_GROUPS,
 194                         Some(src.span().into()),
 195                         |diag_builder| {
 196                             let mut diag_builder = diag_builder.build(&format!(
 197                                 "{}({}) incompatible with previous forbid",
 198                                 level.as_str(),
 199                                 src.name(),
 200                             ));
 201                             decorate_diag(&mut diag_builder);
 202                             diag_builder.emit();
 203                         },
 204                     );
 205                 }
 206
 207                 // Retain the forbid lint level, unless we are
 208                 // issuing a FCW. In the FCW case, we want to
 209                 // respect the new setting.
 210                 if !fcw_warning {
 211                     return;
 212                 }
 213             }
 214         }
 215         if let Level::ForceWarn = old_level {
 216             specs.insert(id, (old_level, old_src));
 217         } else {
 218             specs.insert(id, (level, src));
 219         }
 220     }
 221
 222     /// Pushes a list of AST lint attributes onto this context.
 223     ///
 224     /// This function will return a `BuilderPush` object which should be passed
 225     /// to `pop` when this scope for the attributes provided is exited.
 226     ///
 227     /// This function will perform a number of tasks:
 228     ///
 229     /// * It'll validate all lint-related attributes in `attrs`
 230     /// * It'll mark all lint-related attributes as used
 231     /// * Lint levels will be updated based on the attributes provided
 232     /// * Lint attributes are validated, e.g., a `#[forbid]` can't be switched to
 233     ///   `#[allow]`
 234     ///
 235     /// Don't forget to call `pop`!
 236     pub(crate) fn push(
 237         &mut self,
 238         attrs: &[ast::Attribute],
 239         is_crate_node: bool,
 240         source_hir_id: Option<HirId>,
 241     ) -> BuilderPush {
 242         let mut specs = FxHashMap::default();
 243         let sess = self.sess;
 244         let bad_attr = |span| struct_span_err!(sess, span, E0452, "malformed lint attribute input");
 245         for (attr_index, attr) in attrs.iter().enumerate() {
 246             let level = match Level::from_attr(attr) {
 247                 None => continue,
 248                 Some(Level::Expect(unstable_id)) if let Some(hir_id) = source_hir_id => {
 249                     let stable_id = self.create_stable_id(unstable_id, hir_id, attr_index);
 250
 251                     Level::Expect(stable_id)
 252                 }
 253                 Some(lvl) => lvl,
 254             };
 255
 256             let Some(mut metas) = attr.meta_item_list() else {
 257                 continue
 258             };
 259
 260             if metas.is_empty() {
 261                 // This emits the unused_attributes lint for `#[level()]`
 262                 continue;
 263             }
 264
 265             // Before processing the lint names, look for a reason (RFC 2383)
 266             // at the end.
 267             let mut reason = None;
 268             let tail_li = &metas[metas.len() - 1];
 269             if let Some(item) = tail_li.meta_item() {
 270                 match item.kind {
 271                     ast::MetaItemKind::Word => {} // actual lint names handled later
 272                     ast::MetaItemKind::NameValue(ref name_value) => {
 273                         if item.path == sym::reason {
 274                             if let ast::LitKind::Str(rationale, _) = name_value.kind {
 275                                 if !self.sess.features_untracked().lint_reasons {
 276                                     feature_err(
 277                                         &self.sess.parse_sess,
 278                                         sym::lint_reasons,
 279                                         item.span,
 280                                         "lint reasons are experimental",
 281                                     )
 282                                     .emit();
 283                                 }
 284                                 reason = Some(rationale);
 285                             } else {
 286                                 bad_attr(name_value.span)
 287                                     .span_label(name_value.span, "reason must be a string literal")
 288                                     .emit();
 289                             }
 290                             // found reason, reslice meta list to exclude it
 291                             metas.pop().unwrap();
 292                         } else {
 293                             bad_attr(item.span)
 294                                 .span_label(item.span, "bad attribute argument")
 295                                 .emit();
 296                         }
 297                     }
 298                     ast::MetaItemKind::List(_) => {
 299                         bad_attr(item.span).span_label(item.span, "bad attribute argument").emit();
 300                     }
 301                 }
 302             }
 303
 304             for (lint_index, li) in metas.iter_mut().enumerate() {
 305                 let level = match level {
 306                     Level::Expect(mut id) => {
 307                         id.set_lint_index(Some(lint_index as u16));
 308                         Level::Expect(id)
 309                     }
 310                     level => level,
 311                 };
 312
 313                 let sp = li.span();
 314                 let meta_item = match li {
 315                     ast::NestedMetaItem::MetaItem(meta_item) if meta_item.is_word() => meta_item,
 316                     _ => {
 317                         let mut err = bad_attr(sp);
 318                         let mut add_label = true;
 319                         if let Some(item) = li.meta_item() {
 320                             if let ast::MetaItemKind::NameValue(_) = item.kind {
 321                                 if item.path == sym::reason {
 322                                     err.span_label(sp, "reason in lint attribute must come last");
 323                                     add_label = false;
 324                                 }
 325                             }
 326                         }
 327                         if add_label {
 328                             err.span_label(sp, "bad attribute argument");
 329                         }
 330                         err.emit();
 331                         continue;
 332                     }
 333                 };
 334                 let tool_ident = if meta_item.path.segments.len() > 1 {
 335                     Some(meta_item.path.segments.remove(0).ident)
 336                 } else {
 337                     None
 338                 };
 339                 let tool_name = tool_ident.map(|ident| ident.name);
 340                 let name = pprust::path_to_string(&meta_item.path);
 341                 let lint_result =
 342                     self.store.check_lint_name(&name, tool_name, self.registered_tools);
 343                 match &lint_result {
 344                     CheckLintNameResult::Ok(ids) => {
 345                         let src = LintLevelSource::Node(
 346                             meta_item.path.segments.last().expect("empty lint name").ident.name,
 347                             sp,
 348                             reason,
 349                         );
 350                         for &id in *ids {
 351                             self.check_gated_lint(id, attr.span);
 352                             self.insert_spec(&mut specs, id, (level, src));
 353                         }
 354                         if let Level::Expect(expect_id) = level {
 355                             self.lint_expectations
 356                                 .push((expect_id, LintExpectation::new(reason, sp)));
 357                         }
 358                     }
 359
 360                     CheckLintNameResult::Tool(result) => {
 361                         match *result {
 362                             Ok(ids) => {
 363                                 let complete_name =
 364                                     &format!("{}::{}", tool_ident.unwrap().name, name);
 365                                 let src = LintLevelSource::Node(
 366                                     Symbol::intern(complete_name),
 367                                     sp,
 368                                     reason,
 369                                 );
 370                                 for id in ids {
 371                                     self.insert_spec(&mut specs, *id, (level, src));
 372                                 }
 373                                 if let Level::Expect(expect_id) = level {
 374                                     self.lint_expectations
 375                                         .push((expect_id, LintExpectation::new(reason, sp)));
 376                                 }
 377                             }
 378                             Err((Some(ids), ref new_lint_name)) => {
 379                                 let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 380                                 let (lvl, src) =
 381                                     self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 382                                 struct_lint_level(
 383                                     self.sess,
 384                                     lint,
 385                                     lvl,
 386                                     src,
 387                                     Some(sp.into()),
 388                                     |lint| {
 389                                         let msg = format!(
 390                                             "lint name `{}` is deprecated \
 391                                              and may not have an effect in the future.",
 392                                             name
 393                                         );
 394                                         lint.build(&msg)
 395                                             .span_suggestion(
 396                                                 sp,
 397                                                 "change it to",
 398                                                 new_lint_name.to_string(),
 399                                                 Applicability::MachineApplicable,
 400                                             )
 401                                             .emit();
 402                                     },
 403                                 );
 404
 405                                 let src = LintLevelSource::Node(
 406                                     Symbol::intern(&new_lint_name),
 407                                     sp,
 408                                     reason,
 409                                 );
 410                                 for id in ids {
 411                                     self.insert_spec(&mut specs, *id, (level, src));
 412                                 }
 413                                 if let Level::Expect(expect_id) = level {
 414                                     self.lint_expectations
 415                                         .push((expect_id, LintExpectation::new(reason, sp)));
 416                                 }
 417                             }
 418                             Err((None, _)) => {
 419                                 // If Tool(Err(None, _)) is returned, then either the lint does not
 420                                 // exist in the tool or the code was not compiled with the tool and
 421                                 // therefore the lint was never added to the `LintStore`. To detect
 422                                 // this is the responsibility of the lint tool.
 423                             }
 424                         }
 425                     }
 426
 427                     &CheckLintNameResult::NoTool => {
 428                         let mut err = struct_span_err!(
 429                             sess,
 430                             tool_ident.map_or(DUMMY_SP, |ident| ident.span),
 431                             E0710,
 432                             "unknown tool name `{}` found in scoped lint: `{}::{}`",
 433                             tool_name.unwrap(),
 434                             tool_name.unwrap(),
 435                             pprust::path_to_string(&meta_item.path),
 436                         );
 437                         if sess.is_nightly_build() {
 438                             err.help(&format!(
 439                                 "add `#![register_tool({})]` to the crate root",
 440                                 tool_name.unwrap()
 441                             ));
 442                         }
 443                         err.emit();
 444                         continue;
 445                     }
 446
 447                     _ if !self.warn_about_weird_lints => {}
 448
 449                     CheckLintNameResult::Warning(msg, renamed) => {
 450                         let lint = builtin::RENAMED_AND_REMOVED_LINTS;
 451                         let (renamed_lint_level, src) =
 452                             self.sets.get_lint_level(lint, self.cur, Some(&specs), &sess);
 453                         struct_lint_level(
 454                             self.sess,
 455                             lint,
 456                             renamed_lint_level,
 457                             src,
 458                             Some(sp.into()),
 459                             |lint| {
 460                                 let mut err = lint.build(&msg);
 461                                 if let Some(new_name) = &renamed {
 462                                     err.span_suggestion(
 463                                         sp,
 464                                         "use the new name",
 465                                         new_name.to_string(),
 466                                         Applicability::MachineApplicable,
 467                                     );
 468                                 }
 469                                 err.emit();
 470                             },
 471                         );
 472                     }
 473                     CheckLintNameResult::NoLint(suggestion) => {
 474                         let lint = builtin::UNKNOWN_LINTS;
 475                         let (level, src) =
 476                             self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 477                         struct_lint_level(self.sess, lint, level, src, Some(sp.into()), |lint| {
 478                             let name = if let Some(tool_ident) = tool_ident {
 479                                 format!("{}::{}", tool_ident.name, name)
 480                             } else {
 481                                 name.to_string()
 482                             };
 483                             let mut db = lint.build(&format!("unknown lint: `{}`", name));
 484                             if let Some(suggestion) = suggestion {
 485                                 db.span_suggestion(
 486                                     sp,
 487                                     "did you mean",
 488                                     suggestion.to_string(),
 489                                     Applicability::MachineApplicable,
 490                                 );
 491                             }
 492                             db.emit();
 493                         });
 494                     }
 495                 }
 496                 // If this lint was renamed, apply the new lint instead of ignoring the attribute.
 497                 // This happens outside of the match because the new lint should be applied even if
 498                 // we don't warn about the name change.
 499                 if let CheckLintNameResult::Warning(_, Some(new_name)) = lint_result {
 500                     // Ignore any errors or warnings that happen because the new name is inaccurate
 501                     // NOTE: `new_name` already includes the tool name, so we don't have to add it again.
 502                     if let CheckLintNameResult::Ok(ids) =
 503                         self.store.check_lint_name(&new_name, None, self.registered_tools)
 504                     {
 505                         let src = LintLevelSource::Node(Symbol::intern(&new_name), sp, reason);
 506                         for &id in ids {
 507                             self.check_gated_lint(id, attr.span);
 508                             self.insert_spec(&mut specs, id, (level, src));
 509                         }
 510                         if let Level::Expect(expect_id) = level {
 511                             self.lint_expectations
 512                                 .push((expect_id, LintExpectation::new(reason, sp)));
 513                         }
 514                     } else {
 515                         panic!("renamed lint does not exist: {}", new_name);
 516                     }
 517                 }
 518             }
 519         }
 520
 521         if !is_crate_node {
 522             for (id, &(level, ref src)) in specs.iter() {
 523                 if !id.lint.crate_level_only {
 524                     continue;
 525                 }
 526
 527                 let LintLevelSource::Node(lint_attr_name, lint_attr_span, _) = *src else {
 528                     continue
 529                 };
 530
 531                 let lint = builtin::UNUSED_ATTRIBUTES;
 532                 let (lint_level, lint_src) =
 533                     self.sets.get_lint_level(lint, self.cur, Some(&specs), self.sess);
 534                 struct_lint_level(
 535                     self.sess,
 536                     lint,
 537                     lint_level,
 538                     lint_src,
 539                     Some(lint_attr_span.into()),
 540                     |lint| {
 541                         let mut db = lint.build(&format!(
 542                             "{}({}) is ignored unless specified at crate level",
 543                             level.as_str(),
 544                             lint_attr_name
 545                         ));
 546                         db.emit();
 547                     },
 548                 );
 549                 // don't set a separate error for every lint in the group
 550                 break;
 551             }
 552         }
 553
 554         let prev = self.cur;
 555         if !specs.is_empty() {
 556             self.cur = self.sets.list.push(LintSet { specs, parent: prev });
 557         }
 558
 559         BuilderPush { prev, changed: prev != self.cur }
 560     }
 561
 562     fn create_stable_id(
 563         &mut self,
 564         unstable_id: LintExpectationId,
 565         hir_id: HirId,
 566         attr_index: usize,
 567     ) -> LintExpectationId {
 568         let stable_id =
 569             LintExpectationId::Stable { hir_id, attr_index: attr_index as u16, lint_index: None };
 570
 571         self.expectation_id_map.insert(unstable_id, stable_id);
 572
 573         stable_id
 574     }
 575
 576     /// Checks if the lint is gated on a feature that is not enabled.
 577     fn check_gated_lint(&self, lint_id: LintId, span: Span) {
 578         if let Some(feature) = lint_id.lint.feature_gate {
 579             if !self.sess.features_untracked().enabled(feature) {
 580                 feature_err(
 581                     &self.sess.parse_sess,
 582                     feature,
 583                     span,
 584                     &format!("the `{}` lint is unstable", lint_id.lint.name_lower()),
 585                 )
 586                 .emit();
 587             }
 588         }
 589     }
 590
 591     /// Called after `push` when the scope of a set of attributes are exited.
 592     pub fn pop(&mut self, push: BuilderPush) {
 593         self.cur = push.prev;
 594     }
 595
 596     /// Find the lint level for a lint.
 597     pub fn lint_level(&self, lint: &'static Lint) -> (Level, LintLevelSource) {
 598         self.sets.get_lint_level(lint, self.cur, None, self.sess)
 599     }
 600
 601     /// Used to emit a lint-related diagnostic based on the current state of
 602     /// this lint context.
 603     pub fn struct_lint(
 604         &self,
 605         lint: &'static Lint,
 606         span: Option<MultiSpan>,
 607         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 608     ) {
 609         let (level, src) = self.lint_level(lint);
 610         struct_lint_level(self.sess, lint, level, src, span, decorate)
 611     }
 612
 613     /// Registers the ID provided with the current set of lints stored in
 614     /// this context.
 615     pub fn register_id(&mut self, id: HirId) {
 616         self.id_to_set.insert(id, self.cur);
 617     }
 618
 619     fn update_unstable_expectation_ids(&self) {
 620         self.sess.diagnostic().update_unstable_expectation_id(&self.expectation_id_map);
 621     }
 622
 623     pub fn build_map(self) -> LintLevelMap {
 624         LintLevelMap {
 625             sets: self.sets,
 626             id_to_set: self.id_to_set,
 627             lint_expectations: self.lint_expectations,
 628         }
 629     }
 630 }
 631
 632 struct LintLevelMapBuilder<'tcx> {
 633     levels: LintLevelsBuilder<'tcx>,
 634     tcx: TyCtxt<'tcx>,
 635 }
 636
 637 impl LintLevelMapBuilder<'_> {
 638     fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
 639     where
 640         F: FnOnce(&mut Self),
 641     {
 642         let is_crate_hir = id == hir::CRATE_HIR_ID;
 643         let attrs = self.tcx.hir().attrs(id);
 644         let push = self.levels.push(attrs, is_crate_hir, Some(id));
 645
 646         if push.changed {
 647             self.levels.register_id(id);
 648         }
 649         f(self);
 650         self.levels.pop(push);
 651     }
 652 }
 653
 654 impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
 655     type NestedFilter = nested_filter::All;
 656
 657     fn nested_visit_map(&mut self) -> Self::Map {
 658         self.tcx.hir()
 659     }
 660
 661     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 662         self.with_lint_attrs(param.hir_id, |builder| {
 663             intravisit::walk_param(builder, param);
 664         });
 665     }
 666
 667     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 668         self.with_lint_attrs(it.hir_id(), |builder| {
 669             intravisit::walk_item(builder, it);
 670         });
 671     }
 672
 673     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 674         self.with_lint_attrs(it.hir_id(), |builder| {
 675             intravisit::walk_foreign_item(builder, it);
 676         })
 677     }
 678
 679     fn visit_stmt(&mut self, e: &'tcx hir::Stmt<'tcx>) {
 680         // We will call `with_lint_attrs` when we walk
 681         // the `StmtKind`. The outer statement itself doesn't
 682         // define the lint levels.
 683         intravisit::walk_stmt(self, e);
 684     }
 685
 686     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 687         self.with_lint_attrs(e.hir_id, |builder| {
 688             intravisit::walk_expr(builder, e);
 689         })
 690     }
 691
 692     fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
 693         self.with_lint_attrs(s.hir_id, |builder| {
 694             intravisit::walk_field_def(builder, s);
 695         })
 696     }
 697
 698     fn visit_variant(
 699         &mut self,
 700         v: &'tcx hir::Variant<'tcx>,
 701         g: &'tcx hir::Generics<'tcx>,
 702         item_id: hir::HirId,
 703     ) {
 704         self.with_lint_attrs(v.id, |builder| {
 705             intravisit::walk_variant(builder, v, g, item_id);
 706         })
 707     }
 708
 709     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 710         self.with_lint_attrs(l.hir_id, |builder| {
 711             intravisit::walk_local(builder, l);
 712         })
 713     }
 714
 715     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 716         self.with_lint_attrs(a.hir_id, |builder| {
 717             intravisit::walk_arm(builder, a);
 718         })
 719     }
 720
 721     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 722         self.with_lint_attrs(trait_item.hir_id(), |builder| {
 723             intravisit::walk_trait_item(builder, trait_item);
 724         });
 725     }
 726
 727     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 728         self.with_lint_attrs(impl_item.hir_id(), |builder| {
 729             intravisit::walk_impl_item(builder, impl_item);
 730         });
 731     }
 732 }
 733
 734 pub fn provide(providers: &mut Providers) {
 735     providers.lint_levels = lint_levels;
 736 }