compiler/rustc_lint/src/context.rs

   1 //! Implementation of lint checking.
   2 //!
   3 //! The lint checking is mostly consolidated into one pass which runs
   4 //! after all other analyses. Throughout compilation, lint warnings
   5 //! can be added via the `add_lint` method on the Session structure. This
   6 //! requires a span and an ID of the node that the lint is being added to. The
   7 //! lint isn't actually emitted at that time because it is unknown what the
   8 //! actual lint level at that location is.
   9 //!
  10 //! To actually emit lint warnings/errors, a separate pass is used.
  11 //! A context keeps track of the current state of all lint levels.
  12 //! Upon entering a node of the ast which can modify the lint settings, the
  13 //! previous lint state is pushed onto a stack and the ast is then recursed
  14 //! upon. As the ast is traversed, this keeps track of the current lint level
  15 //! for all lint attributes.
  16
  17 use self::TargetLint::*;
  18
  19 use crate::errors::{
  20     CheckNameDeprecated, CheckNameUnknown, CheckNameUnknownTool, CheckNameWarning, RequestedLevel,
  21     UnsupportedGroup,
  22 };
  23 use crate::levels::LintLevelsBuilder;
  24 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
  25 use rustc_ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
  26 use rustc_data_structures::fx::FxHashMap;
  27 use rustc_data_structures::sync;
  28 use rustc_errors::add_elided_lifetime_in_path_suggestion;
  29 use rustc_errors::{
  30     Applicability, DecorateLint, LintDiagnosticBuilder, MultiSpan, SuggestionStyle,
  31 };
  32 use rustc_hir as hir;
  33 use rustc_hir::def::Res;
  34 use rustc_hir::def_id::{CrateNum, DefId};
  35 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  36 use rustc_middle::middle::privacy::AccessLevels;
  37 use rustc_middle::middle::stability;
  38 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  39 use rustc_middle::ty::print::with_no_trimmed_paths;
  40 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
  41 use rustc_session::lint::{BuiltinLintDiagnostics, LintExpectationId};
  42 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  43 use rustc_session::Session;
  44 use rustc_span::lev_distance::find_best_match_for_name;
  45 use rustc_span::symbol::{sym, Ident, Symbol};
  46 use rustc_span::{BytePos, Span};
  47 use rustc_target::abi;
  48
  49 use std::cell::Cell;
  50 use std::iter;
  51 use std::slice;
  52
  53 /// Information about the registered lints.
  54 ///
  55 /// This is basically the subset of `Context` that we can
  56 /// build early in the compile pipeline.
  57 pub struct LintStore {
  58     /// Registered lints.
  59     lints: Vec<&'static Lint>,
  60
  61     /// Constructor functions for each variety of lint pass.
  62     ///
  63     /// These should only be called once, but since we want to avoid locks or
  64     /// interior mutability, we don't enforce this (and lints should, in theory,
  65     /// be compatible with being constructed more than once, though not
  66     /// necessarily in a sane manner. This is safe though.)
  67     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  68     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  69     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  70     /// This is unique in that we construct them per-module, so not once.
  71     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  72
  73     /// Lints indexed by name.
  74     by_name: FxHashMap<String, TargetLint>,
  75
  76     /// Map of registered lint groups to what lints they expand to.
  77     lint_groups: FxHashMap<&'static str, LintGroup>,
  78 }
  79
  80 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  81 #[derive(Debug)]
  82 enum TargetLint {
  83     /// A direct lint target
  84     Id(LintId),
  85
  86     /// Temporary renaming, used for easing migration pain; see #16545
  87     Renamed(String, LintId),
  88
  89     /// Lint with this name existed previously, but has been removed/deprecated.
  90     /// The string argument is the reason for removal.
  91     Removed(String),
  92
  93     /// A lint name that should give no warnings and have no effect.
  94     ///
  95     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  96     Ignored,
  97 }
  98
  99 pub enum FindLintError {
 100     NotFound,
 101     Removed,
 102 }
 103
 104 struct LintAlias {
 105     name: &'static str,
 106     /// Whether deprecation warnings should be suppressed for this alias.
 107     silent: bool,
 108 }
 109
 110 struct LintGroup {
 111     lint_ids: Vec<LintId>,
 112     from_plugin: bool,
 113     depr: Option<LintAlias>,
 114 }
 115
 116 #[derive(Debug)]
 117 pub enum CheckLintNameResult<'a> {
 118     Ok(&'a [LintId]),
 119     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 120     NoLint(Option<Symbol>),
 121     /// The lint refers to a tool that has not been registered.
 122     NoTool,
 123     /// The lint is either renamed or removed. This is the warning
 124     /// message, and an optional new name (`None` if removed).
 125     Warning(String, Option<String>),
 126     /// The lint is from a tool. If the Option is None, then either
 127     /// the lint does not exist in the tool or the code was not
 128     /// compiled with the tool and therefore the lint was never
 129     /// added to the `LintStore`. Otherwise the `LintId` will be
 130     /// returned as if it where a rustc lint.
 131     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 132 }
 133
 134 impl LintStore {
 135     pub fn new() -> LintStore {
 136         LintStore {
 137             lints: vec![],
 138             pre_expansion_passes: vec![],
 139             early_passes: vec![],
 140             late_passes: vec![],
 141             late_module_passes: vec![],
 142             by_name: Default::default(),
 143             lint_groups: Default::default(),
 144         }
 145     }
 146
 147     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 148         &self.lints
 149     }
 150
 151     pub fn get_lint_groups<'t>(
 152         &'t self,
 153     ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
 154         // This function is not used in a way which observes the order of lints.
 155         #[allow(rustc::potential_query_instability)]
 156         self.lint_groups
 157             .iter()
 158             .filter(|(_, LintGroup { depr, .. })| {
 159                 // Don't display deprecated lint groups.
 160                 depr.is_none()
 161             })
 162             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 163                 (*k, lint_ids.clone(), *from_plugin)
 164             })
 165     }
 166
 167     pub fn register_early_pass(
 168         &mut self,
 169         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 170     ) {
 171         self.early_passes.push(Box::new(pass));
 172     }
 173
 174     /// This lint pass is softly deprecated. It misses expanded code and has caused a few
 175     /// errors in the past. Currently, it is only used in Clippy. New implementations
 176     /// should avoid using this interface, as it might be removed in the future.
 177     ///
 178     /// * See [rust#69838](https://github.com/rust-lang/rust/pull/69838)
 179     /// * See [rust-clippy#5518](https://github.com/rust-lang/rust-clippy/pull/5518)
 180     pub fn register_pre_expansion_pass(
 181         &mut self,
 182         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 183     ) {
 184         self.pre_expansion_passes.push(Box::new(pass));
 185     }
 186
 187     pub fn register_late_pass(
 188         &mut self,
 189         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 190     ) {
 191         self.late_passes.push(Box::new(pass));
 192     }
 193
 194     pub fn register_late_mod_pass(
 195         &mut self,
 196         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 197     ) {
 198         self.late_module_passes.push(Box::new(pass));
 199     }
 200
 201     // Helper method for register_early/late_pass
 202     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 203         for lint in lints {
 204             self.lints.push(lint);
 205
 206             let id = LintId::of(lint);
 207             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 208                 bug!("duplicate specification of lint {}", lint.name_lower())
 209             }
 210
 211             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 212                 if let Some(edition) = reason.edition() {
 213                     self.lint_groups
 214                         .entry(edition.lint_name())
 215                         .or_insert(LintGroup {
 216                             lint_ids: vec![],
 217                             from_plugin: lint.is_plugin,
 218                             depr: None,
 219                         })
 220                         .lint_ids
 221                         .push(id);
 222                 } else {
 223                     // Lints belonging to the `future_incompatible` lint group are lints where a
 224                     // future version of rustc will cause existing code to stop compiling.
 225                     // Lints tied to an edition don't count because they are opt-in.
 226                     self.lint_groups
 227                         .entry("future_incompatible")
 228                         .or_insert(LintGroup {
 229                             lint_ids: vec![],
 230                             from_plugin: lint.is_plugin,
 231                             depr: None,
 232                         })
 233                         .lint_ids
 234                         .push(id);
 235                 }
 236             }
 237         }
 238     }
 239
 240     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 241         self.lint_groups.insert(
 242             alias,
 243             LintGroup {
 244                 lint_ids: vec![],
 245                 from_plugin: false,
 246                 depr: Some(LintAlias { name: lint_name, silent: true }),
 247             },
 248         );
 249     }
 250
 251     pub fn register_group(
 252         &mut self,
 253         from_plugin: bool,
 254         name: &'static str,
 255         deprecated_name: Option<&'static str>,
 256         to: Vec<LintId>,
 257     ) {
 258         let new = self
 259             .lint_groups
 260             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 261             .is_none();
 262         if let Some(deprecated) = deprecated_name {
 263             self.lint_groups.insert(
 264                 deprecated,
 265                 LintGroup {
 266                     lint_ids: vec![],
 267                     from_plugin,
 268                     depr: Some(LintAlias { name, silent: false }),
 269                 },
 270             );
 271         }
 272
 273         if !new {
 274             bug!("duplicate specification of lint group {}", name);
 275         }
 276     }
 277
 278     /// This lint should give no warning and have no effect.
 279     ///
 280     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 281     #[track_caller]
 282     pub fn register_ignored(&mut self, name: &str) {
 283         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 284             bug!("duplicate specification of lint {}", name);
 285         }
 286     }
 287
 288     /// This lint has been renamed; warn about using the new name and apply the lint.
 289     #[track_caller]
 290     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 291         let Some(&Id(target)) = self.by_name.get(new_name) else {
 292             bug!("invalid lint renaming of {} to {}", old_name, new_name);
 293         };
 294         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 295     }
 296
 297     pub fn register_removed(&mut self, name: &str, reason: &str) {
 298         self.by_name.insert(name.into(), Removed(reason.into()));
 299     }
 300
 301     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 302         match self.by_name.get(lint_name) {
 303             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 304             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 305             Some(&Removed(_)) => Err(FindLintError::Removed),
 306             Some(&Ignored) => Ok(vec![]),
 307             None => loop {
 308                 return match self.lint_groups.get(lint_name) {
 309                     Some(LintGroup { lint_ids, depr, .. }) => {
 310                         if let Some(LintAlias { name, .. }) = depr {
 311                             lint_name = name;
 312                             continue;
 313                         }
 314                         Ok(lint_ids.clone())
 315                     }
 316                     None => Err(FindLintError::Removed),
 317                 };
 318             },
 319         }
 320     }
 321
 322     /// Checks the validity of lint names derived from the command line.
 323     pub fn check_lint_name_cmdline(
 324         &self,
 325         sess: &Session,
 326         lint_name: &str,
 327         level: Level,
 328         registered_tools: &RegisteredTools,
 329     ) {
 330         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 331         if lint_name_only == crate::WARNINGS.name_lower() && matches!(level, Level::ForceWarn(_)) {
 332             sess.emit_err(UnsupportedGroup { lint_group: crate::WARNINGS.name_lower() });
 333             return;
 334         }
 335         let lint_name = lint_name.to_string();
 336         match self.check_lint_name(lint_name_only, tool_name, registered_tools) {
 337             CheckLintNameResult::Warning(msg, _) => {
 338                 sess.emit_warning(CheckNameWarning {
 339                     msg,
 340                     sub: RequestedLevel { level, lint_name },
 341                 });
 342             }
 343             CheckLintNameResult::NoLint(suggestion) => {
 344                 sess.emit_err(CheckNameUnknown {
 345                     lint_name: lint_name.clone(),
 346                     suggestion,
 347                     sub: RequestedLevel { level, lint_name },
 348                 });
 349             }
 350             CheckLintNameResult::Tool(result) => {
 351                 if let Err((Some(_), new_name)) = result {
 352                     sess.emit_warning(CheckNameDeprecated {
 353                         lint_name: lint_name.clone(),
 354                         new_name,
 355                         sub: RequestedLevel { level, lint_name },
 356                     });
 357                 }
 358             }
 359             CheckLintNameResult::NoTool => {
 360                 sess.emit_err(CheckNameUnknownTool {
 361                     tool_name: tool_name.unwrap(),
 362                     sub: RequestedLevel { level, lint_name },
 363                 });
 364             }
 365             _ => {}
 366         };
 367     }
 368
 369     /// True if this symbol represents a lint group name.
 370     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 371         debug!(
 372             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 373             lint_name,
 374             self.lint_groups.keys().collect::<Vec<_>>()
 375         );
 376         let lint_name_str = lint_name.as_str();
 377         self.lint_groups.contains_key(lint_name_str) || {
 378             let warnings_name_str = crate::WARNINGS.name_lower();
 379             lint_name_str == warnings_name_str
 380         }
 381     }
 382
 383     /// Checks the name of a lint for its existence, and whether it was
 384     /// renamed or removed. Generates a DiagnosticBuilder containing a
 385     /// warning for renamed and removed lints. This is over both lint
 386     /// names from attributes and those passed on the command line. Since
 387     /// it emits non-fatal warnings and there are *two* lint passes that
 388     /// inspect attributes, this is only run from the late pass to avoid
 389     /// printing duplicate warnings.
 390     pub fn check_lint_name(
 391         &self,
 392         lint_name: &str,
 393         tool_name: Option<Symbol>,
 394         registered_tools: &RegisteredTools,
 395     ) -> CheckLintNameResult<'_> {
 396         if let Some(tool_name) = tool_name {
 397             // FIXME: rustc and rustdoc are considered tools for lints, but not for attributes.
 398             if tool_name != sym::rustc
 399                 && tool_name != sym::rustdoc
 400                 && !registered_tools.contains(&Ident::with_dummy_span(tool_name))
 401             {
 402                 return CheckLintNameResult::NoTool;
 403             }
 404         }
 405
 406         let complete_name = if let Some(tool_name) = tool_name {
 407             format!("{}::{}", tool_name, lint_name)
 408         } else {
 409             lint_name.to_string()
 410         };
 411         // If the lint was scoped with `tool::` check if the tool lint exists
 412         if let Some(tool_name) = tool_name {
 413             match self.by_name.get(&complete_name) {
 414                 None => match self.lint_groups.get(&*complete_name) {
 415                     // If the lint isn't registered, there are two possibilities:
 416                     None => {
 417                         // 1. The tool is currently running, so this lint really doesn't exist.
 418                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 419                         debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 420                         let tool_prefix = format!("{}::", tool_name);
 421                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 422                             self.no_lint_suggestion(&complete_name)
 423                         } else {
 424                             // 2. The tool isn't currently running, so no lints will be registered.
 425                             // To avoid giving a false positive, ignore all unknown lints.
 426                             CheckLintNameResult::Tool(Err((None, String::new())))
 427                         };
 428                     }
 429                     Some(LintGroup { lint_ids, .. }) => {
 430                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 431                     }
 432                 },
 433                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 434                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 435                 // to treat tool_lints and rustc lints different and can use the code below.
 436                 _ => {}
 437             }
 438         }
 439         match self.by_name.get(&complete_name) {
 440             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 441                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 442                 Some(new_name.to_owned()),
 443             ),
 444             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 445                 format!("lint `{}` has been removed: {}", complete_name, reason),
 446                 None,
 447             ),
 448             None => match self.lint_groups.get(&*complete_name) {
 449                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 450                 // variant of this lint
 451                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 452                 Some(LintGroup { lint_ids, depr, .. }) => {
 453                     // Check if the lint group name is deprecated
 454                     if let Some(LintAlias { name, silent }) = depr {
 455                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 456                         return if *silent {
 457                             CheckLintNameResult::Ok(&lint_ids)
 458                         } else {
 459                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 460                         };
 461                     }
 462                     CheckLintNameResult::Ok(&lint_ids)
 463                 }
 464             },
 465             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 466             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 467         }
 468     }
 469
 470     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 471         let name_lower = lint_name.to_lowercase();
 472
 473         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 474             // First check if the lint name is (partly) in upper case instead of lower case...
 475             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 476         }
 477         // ...if not, search for lints with a similar name
 478         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 479         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 480         let names: Vec<Symbol> = groups.chain(lints).collect();
 481         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 482         CheckLintNameResult::NoLint(suggestion)
 483     }
 484
 485     fn check_tool_name_for_backwards_compat(
 486         &self,
 487         lint_name: &str,
 488         tool_name: &str,
 489     ) -> CheckLintNameResult<'_> {
 490         let complete_name = format!("{}::{}", tool_name, lint_name);
 491         match self.by_name.get(&complete_name) {
 492             None => match self.lint_groups.get(&*complete_name) {
 493                 // Now we are sure, that this lint exists nowhere
 494                 None => self.no_lint_suggestion(lint_name),
 495                 Some(LintGroup { lint_ids, depr, .. }) => {
 496                     // Reaching this would be weird, but let's cover this case anyway
 497                     if let Some(LintAlias { name, silent }) = depr {
 498                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 499                         return if *silent {
 500                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 501                         } else {
 502                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 503                         };
 504                     }
 505                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 506                 }
 507             },
 508             Some(&Id(ref id)) => {
 509                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 510             }
 511             Some(other) => {
 512                 debug!("got renamed lint {:?}", other);
 513                 CheckLintNameResult::NoLint(None)
 514             }
 515         }
 516     }
 517 }
 518
 519 /// Context for lint checking outside of type inference.
 520 pub struct LateContext<'tcx> {
 521     /// Type context we're checking in.
 522     pub tcx: TyCtxt<'tcx>,
 523
 524     /// Current body, or `None` if outside a body.
 525     pub enclosing_body: Option<hir::BodyId>,
 526
 527     /// Type-checking results for the current body. Access using the `typeck_results`
 528     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 529     // FIXME(eddyb) move all the code accessing internal fields like this,
 530     // to this module, to avoid exposing it to lint logic.
 531     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 532
 533     /// Parameter environment for the item we are in.
 534     pub param_env: ty::ParamEnv<'tcx>,
 535
 536     /// Items accessible from the crate being checked.
 537     pub access_levels: &'tcx AccessLevels,
 538
 539     /// The store of registered lints and the lint levels.
 540     pub lint_store: &'tcx LintStore,
 541
 542     pub last_node_with_lint_attrs: hir::HirId,
 543
 544     /// Generic type parameters in scope for the item we are in.
 545     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 546
 547     /// We are only looking at one module
 548     pub only_module: bool,
 549 }
 550
 551 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 552 pub struct EarlyContext<'a> {
 553     pub builder: LintLevelsBuilder<'a>,
 554     pub buffered: LintBuffer,
 555 }
 556
 557 pub trait LintPassObject: Sized {}
 558
 559 impl LintPassObject for EarlyLintPassObject {}
 560
 561 impl LintPassObject for LateLintPassObject {}
 562
 563 pub trait LintContext: Sized {
 564     type PassObject: LintPassObject;
 565
 566     fn sess(&self) -> &Session;
 567     fn lints(&self) -> &LintStore;
 568
 569     fn lookup_with_diagnostics(
 570         &self,
 571         lint: &'static Lint,
 572         span: Option<impl Into<MultiSpan>>,
 573         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 574         diagnostic: BuiltinLintDiagnostics,
 575     ) {
 576         self.lookup(lint, span, |lint| {
 577             // We first generate a blank diagnostic.
 578             let mut db = lint.build("");
 579
 580             // Now, set up surrounding context.
 581             let sess = self.sess();
 582             match diagnostic {
 583                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
 584                     let spans: Vec<_> = content
 585                         .char_indices()
 586                         .filter_map(|(i, c)| {
 587                             TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
 588                                 let lo = span.lo() + BytePos(2 + i as u32);
 589                                 (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
 590                             })
 591                         })
 592                         .collect();
 593                     let (an, s) = match spans.len() {
 594                         1 => ("an ", ""),
 595                         _ => ("", "s"),
 596                     };
 597                     db.span_label(span, &format!(
 598                         "this comment contains {}invisible unicode text flow control codepoint{}",
 599                         an,
 600                         s,
 601                     ));
 602                     for (c, span) in &spans {
 603                         db.span_label(*span, format!("{:?}", c));
 604                     }
 605                     db.note(
 606                         "these kind of unicode codepoints change the way text flows on \
 607                          applications that support them, but can cause confusion because they \
 608                          change the order of characters on the screen",
 609                     );
 610                     if !spans.is_empty() {
 611                         db.multipart_suggestion_with_style(
 612                             "if their presence wasn't intentional, you can remove them",
 613                             spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
 614                             Applicability::MachineApplicable,
 615                             SuggestionStyle::HideCodeAlways,
 616                         );
 617                     }
 618                 },
 619                 BuiltinLintDiagnostics::Normal => (),
 620                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 621                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 622                         Ok(ref s) => {
 623                             // FIXME(Manishearth) ideally the emitting code
 624                             // can tell us whether or not this is global
 625                             let opt_colon =
 626                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 627
 628                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 629                         }
 630                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 631                     };
 632                     db.span_suggestion(span, "use `crate`", sugg, app);
 633                 }
 634                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 635                     db.span_label(
 636                         span,
 637                         "names from parent modules are not accessible without an explicit import",
 638                     );
 639                 }
 640                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 641                     span_def,
 642                 ) => {
 643                     db.span_note(span_def, "the macro is defined here");
 644                 }
 645                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 646                     n,
 647                     path_span,
 648                     incl_angl_brckt,
 649                     insertion_span,
 650                 ) => {
 651                     add_elided_lifetime_in_path_suggestion(
 652                         sess.source_map(),
 653                         &mut db,
 654                         n,
 655                         path_span,
 656                         incl_angl_brckt,
 657                         insertion_span,
 658                     );
 659                 }
 660                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 661                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 662                 }
 663                 BuiltinLintDiagnostics::UnusedImports(message, replaces, in_test_module) => {
 664                     if !replaces.is_empty() {
 665                         db.tool_only_multipart_suggestion(
 666                             &message,
 667                             replaces,
 668                             Applicability::MachineApplicable,
 669                         );
 670                     }
 671
 672                     if let Some(span) = in_test_module {
 673                         db.span_help(
 674                             self.sess().source_map().guess_head_span(span),
 675                             "consider adding a `#[cfg(test)]` to the containing module",
 676                         );
 677                     }
 678                 }
 679                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 680                     for (span, is_imported) in spans {
 681                         let introduced = if is_imported { "imported" } else { "defined" };
 682                         db.span_label(
 683                             span,
 684                             format!("the item `{}` is already {} here", ident, introduced),
 685                         );
 686                     }
 687                 }
 688                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 689                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 690                 }
 691                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 692                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 693                     db.help("to document an item produced by a macro, \
 694                                   the macro must produce the documentation as part of its expansion");
 695                 }
 696                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 697                     db.span_suggestion(span, "remove `mut` from the parameter", ident, Applicability::MachineApplicable);
 698                 }
 699                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 700                     db.span_label(span, "ABI should be specified here");
 701                     db.help(&format!("the default ABI is {}", default_abi.name()));
 702                 }
 703                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 704                     db.span_label(span, "the attribute is introduced here");
 705                 }
 706                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 707                     db.note(&note);
 708                 }
 709                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 710                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 711                 }
 712                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 713                     db.span_label(span, "unknown prefix");
 714                     db.span_suggestion_verbose(
 715                         span.shrink_to_hi(),
 716                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 717                         " ",
 718                         Applicability::MachineApplicable,
 719                     );
 720                 }
 721                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 722                     attr_name,
 723                     macro_name,
 724                     invoc_span
 725                 } => {
 726                     db.span_note(
 727                         invoc_span,
 728                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 729                     );
 730                 }
 731                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 732                     if is_trailing {
 733                         db.note("macro invocations at the end of a block are treated as expressions");
 734                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 735                     }
 736                 }
 737                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 738                     db.multipart_suggestion(
 739                         "wrap this expression in parentheses",
 740                         vec![(span.shrink_to_lo(), "(".to_string()),
 741                              (span.shrink_to_hi(), ")".to_string())],
 742                         Applicability::MachineApplicable
 743                     );
 744                 }
 745                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 746                     db.help(&help);
 747                     db.note("see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information");
 748                 },
 749                 BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), None) => {
 750                     let Some(names_valid) = &sess.parse_sess.check_config.names_valid else {
 751                         bug!("it shouldn't be possible to have a diagnostic on a name if name checking is not enabled");
 752                     };
 753                     let possibilities: Vec<Symbol> = names_valid.iter().map(|s| *s).collect();
 754
 755                     // Suggest the most probable if we found one
 756                     if let Some(best_match) = find_best_match_for_name(&possibilities, name, None) {
 757                         db.span_suggestion(name_span, "did you mean", best_match, Applicability::MaybeIncorrect);
 758                     }
 759                 },
 760                 BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), Some((value, value_span))) => {
 761                     let Some(values) = &sess.parse_sess.check_config.values_valid.get(&name) else {
 762                         bug!("it shouldn't be possible to have a diagnostic on a value whose name is not in values");
 763                     };
 764                     let possibilities: Vec<Symbol> = values.iter().map(|&s| s).collect();
 765
 766                     // Show the full list if all possible values for a given name, but don't do it
 767                     // for names as the possibilities could be very long
 768                     if !possibilities.is_empty() {
 769                         {
 770                             let mut possibilities = possibilities.iter().map(Symbol::as_str).collect::<Vec<_>>();
 771                             possibilities.sort();
 772
 773                             let possibilities = possibilities.join(", ");
 774                             db.note(&format!("expected values for `{name}` are: {possibilities}"));
 775                         }
 776
 777                         // Suggest the most probable if we found one
 778                         if let Some(best_match) = find_best_match_for_name(&possibilities, value, None) {
 779                             db.span_suggestion(value_span, "did you mean", format!("\"{best_match}\""), Applicability::MaybeIncorrect);
 780                         }
 781                     } else {
 782                         db.note(&format!("no expected value for `{name}`"));
 783                         if name != sym::feature {
 784                             db.span_suggestion(name_span.shrink_to_hi().to(value_span), "remove the value", "", Applicability::MaybeIncorrect);
 785                         }
 786                     }
 787                 },
 788                 BuiltinLintDiagnostics::DeprecatedWhereclauseLocation(new_span, suggestion) => {
 789                     db.multipart_suggestion(
 790                         "move it to the end of the type declaration",
 791                         vec![(db.span.primary_span().unwrap(), "".to_string()), (new_span, suggestion)],
 792                         Applicability::MachineApplicable,
 793                     );
 794                     db.note(
 795                         "see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information",
 796                     );
 797                 },
 798                 BuiltinLintDiagnostics::SingleUseLifetime {
 799                     param_span,
 800                     use_span: Some((use_span, elide)),
 801                     deletion_span,
 802                 } => {
 803                     debug!(?param_span, ?use_span, ?deletion_span);
 804                     db.span_label(param_span, "this lifetime...");
 805                     db.span_label(use_span, "...is used only here");
 806                     let msg = "elide the single-use lifetime";
 807                     let (use_span, replace_lt) = if elide {
 808                         let use_span = sess.source_map().span_extend_while(
 809                             use_span,
 810                             char::is_whitespace,
 811                         ).unwrap_or(use_span);
 812                         (use_span, String::new())
 813                     } else {
 814                         (use_span, "'_".to_owned())
 815                     };
 816                     db.multipart_suggestion(
 817                         msg,
 818                         vec![(deletion_span, String::new()), (use_span, replace_lt)],
 819                         Applicability::MachineApplicable,
 820                     );
 821                 },
 822                 BuiltinLintDiagnostics::SingleUseLifetime {
 823                     param_span: _,
 824                     use_span: None,
 825                     deletion_span,
 826                 } => {
 827                     debug!(?deletion_span);
 828                     db.span_suggestion(
 829                         deletion_span,
 830                         "elide the unused lifetime",
 831                         "",
 832                         Applicability::MachineApplicable,
 833                     );
 834                 },
 835                 BuiltinLintDiagnostics::NamedArgumentUsedPositionally{ position_sp_to_replace, position_sp_for_msg, named_arg_sp, named_arg_name, is_formatting_arg} => {
 836                     db.span_label(named_arg_sp, "this named argument is referred to by position in formatting string");
 837                     if let Some(positional_arg_for_msg) = position_sp_for_msg {
 838                         let msg = format!("this formatting argument uses named argument `{}` by position", named_arg_name);
 839                         db.span_label(positional_arg_for_msg, msg);
 840                     }
 841
 842                     if let Some(positional_arg_to_replace) = position_sp_to_replace {
 843                         let name = if is_formatting_arg { named_arg_name + "$" } else { named_arg_name };
 844                         let span_to_replace = if let Ok(positional_arg_content) =
 845                             self.sess().source_map().span_to_snippet(positional_arg_to_replace) && positional_arg_content.starts_with(":") {
 846                             positional_arg_to_replace.shrink_to_lo()
 847                         } else {
 848                             positional_arg_to_replace
 849                         };
 850                         db.span_suggestion_verbose(
 851                             span_to_replace,
 852                             "use the named argument by name to avoid ambiguity",
 853                             name,
 854                             Applicability::MaybeIncorrect,
 855                         );
 856                     }
 857                 }
 858             }
 859             // Rewrap `db`, and pass control to the user.
 860             decorate(LintDiagnosticBuilder::new(db));
 861         });
 862     }
 863
 864     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 865     // set the span in their `decorate` function (preferably using set_span).
 866     fn lookup<S: Into<MultiSpan>>(
 867         &self,
 868         lint: &'static Lint,
 869         span: Option<S>,
 870         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 871     );
 872
 873     /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
 874     /// typically generated by `#[derive(LintDiagnostic)]`).
 875     fn emit_spanned_lint<S: Into<MultiSpan>>(
 876         &self,
 877         lint: &'static Lint,
 878         span: S,
 879         decorator: impl for<'a> DecorateLint<'a, ()>,
 880     ) {
 881         self.lookup(lint, Some(span), |diag| decorator.decorate_lint(diag));
 882     }
 883
 884     fn struct_span_lint<S: Into<MultiSpan>>(
 885         &self,
 886         lint: &'static Lint,
 887         span: S,
 888         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 889     ) {
 890         self.lookup(lint, Some(span), decorate);
 891     }
 892
 893     /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
 894     /// generated by `#[derive(LintDiagnostic)]`).
 895     fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
 896         self.lookup(lint, None as Option<Span>, |diag| decorator.decorate_lint(diag));
 897     }
 898
 899     /// Emit a lint at the appropriate level, with no associated span.
 900     fn lint(
 901         &self,
 902         lint: &'static Lint,
 903         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 904     ) {
 905         self.lookup(lint, None as Option<Span>, decorate);
 906     }
 907
 908     /// This returns the lint level for the given lint at the current location.
 909     fn get_lint_level(&self, lint: &'static Lint) -> Level;
 910
 911     /// This function can be used to manually fulfill an expectation. This can
 912     /// be used for lints which contain several spans, and should be suppressed,
 913     /// if either location was marked with an expectation.
 914     ///
 915     /// Note that this function should only be called for [`LintExpectationId`]s
 916     /// retrieved from the current lint pass. Buffered or manually created ids can
 917     /// cause ICEs.
 918     fn fulfill_expectation(&self, expectation: LintExpectationId) {
 919         // We need to make sure that submitted expectation ids are correctly fulfilled suppressed
 920         // and stored between compilation sessions. To not manually do these steps, we simply create
 921         // a dummy diagnostic and emit is as usual, which will be suppressed and stored like a normal
 922         // expected lint diagnostic.
 923         self.sess()
 924             .struct_expect(
 925                 "this is a dummy diagnostic, to submit and store an expectation",
 926                 expectation,
 927             )
 928             .emit();
 929     }
 930 }
 931
 932 impl<'a> EarlyContext<'a> {
 933     pub(crate) fn new(
 934         sess: &'a Session,
 935         warn_about_weird_lints: bool,
 936         lint_store: &'a LintStore,
 937         registered_tools: &'a RegisteredTools,
 938         buffered: LintBuffer,
 939     ) -> EarlyContext<'a> {
 940         EarlyContext {
 941             builder: LintLevelsBuilder::new(
 942                 sess,
 943                 warn_about_weird_lints,
 944                 lint_store,
 945                 registered_tools,
 946             ),
 947             buffered,
 948         }
 949     }
 950 }
 951
 952 impl LintContext for LateContext<'_> {
 953     type PassObject = LateLintPassObject;
 954
 955     /// Gets the overall compiler `Session` object.
 956     fn sess(&self) -> &Session {
 957         &self.tcx.sess
 958     }
 959
 960     fn lints(&self) -> &LintStore {
 961         &*self.lint_store
 962     }
 963
 964     fn lookup<S: Into<MultiSpan>>(
 965         &self,
 966         lint: &'static Lint,
 967         span: Option<S>,
 968         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 969     ) {
 970         let hir_id = self.last_node_with_lint_attrs;
 971
 972         match span {
 973             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 974             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 975         }
 976     }
 977
 978     fn get_lint_level(&self, lint: &'static Lint) -> Level {
 979         self.tcx.lint_level_at_node(lint, self.last_node_with_lint_attrs).0
 980     }
 981 }
 982
 983 impl LintContext for EarlyContext<'_> {
 984     type PassObject = EarlyLintPassObject;
 985
 986     /// Gets the overall compiler `Session` object.
 987     fn sess(&self) -> &Session {
 988         &self.builder.sess()
 989     }
 990
 991     fn lints(&self) -> &LintStore {
 992         self.builder.lint_store()
 993     }
 994
 995     fn lookup<S: Into<MultiSpan>>(
 996         &self,
 997         lint: &'static Lint,
 998         span: Option<S>,
 999         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
1000     ) {
1001         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
1002     }
1003
1004     fn get_lint_level(&self, lint: &'static Lint) -> Level {
1005         self.builder.lint_level(lint).0
1006     }
1007 }
1008
1009 impl<'tcx> LateContext<'tcx> {
1010     /// Gets the type-checking results for the current body,
1011     /// or `None` if outside a body.
1012     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
1013         self.cached_typeck_results.get().or_else(|| {
1014             self.enclosing_body.map(|body| {
1015                 let typeck_results = self.tcx.typeck_body(body);
1016                 self.cached_typeck_results.set(Some(typeck_results));
1017                 typeck_results
1018             })
1019         })
1020     }
1021
1022     /// Gets the type-checking results for the current body.
1023     /// As this will ICE if called outside bodies, only call when working with
1024     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
1025     #[track_caller]
1026     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
1027         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
1028     }
1029
1030     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
1031     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
1032     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
1033     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
1034         match *qpath {
1035             hir::QPath::Resolved(_, ref path) => path.res,
1036             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
1037                 .maybe_typeck_results()
1038                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
1039                 .or_else(|| {
1040                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
1041                         Some(self.tcx.typeck(id.owner))
1042                     } else {
1043                         None
1044                     }
1045                 })
1046                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
1047                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
1048         }
1049     }
1050
1051     /// Check if a `DefId`'s path matches the given absolute type path usage.
1052     ///
1053     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
1054     /// inherent `impl` blocks are matched with the name of the type.
1055     ///
1056     /// Instead of using this method, it is often preferable to instead use
1057     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
1058     /// as paths get invalidated if the target definition moves.
1059     ///
1060     /// # Examples
1061     ///
1062     /// ```rust,ignore (no context or def id available)
1063     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
1064     ///     // The given `def_id` is that of an `Option` type
1065     /// }
1066     /// ```
1067     ///
1068     /// Used by clippy, but should be replaced by diagnostic items eventually.
1069     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
1070         let names = self.get_def_path(def_id);
1071
1072         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
1073     }
1074
1075     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
1076     ///
1077     /// # Examples
1078     ///
1079     /// ```rust,ignore (no context or def id available)
1080     /// let def_path = cx.get_def_path(def_id);
1081     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
1082     ///     // The given `def_id` is that of an `Option` type
1083     /// }
1084     /// ```
1085     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
1086         pub struct AbsolutePathPrinter<'tcx> {
1087             pub tcx: TyCtxt<'tcx>,
1088         }
1089
1090         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
1091             type Error = !;
1092
1093             type Path = Vec<Symbol>;
1094             type Region = ();
1095             type Type = ();
1096             type DynExistential = ();
1097             type Const = ();
1098
1099             fn tcx(&self) -> TyCtxt<'tcx> {
1100                 self.tcx
1101             }
1102
1103             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
1104                 Ok(())
1105             }
1106
1107             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
1108                 Ok(())
1109             }
1110
1111             fn print_dyn_existential(
1112                 self,
1113                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
1114             ) -> Result<Self::DynExistential, Self::Error> {
1115                 Ok(())
1116             }
1117
1118             fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1119                 Ok(())
1120             }
1121
1122             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1123                 Ok(vec![self.tcx.crate_name(cnum)])
1124             }
1125
1126             fn path_qualified(
1127                 self,
1128                 self_ty: Ty<'tcx>,
1129                 trait_ref: Option<ty::TraitRef<'tcx>>,
1130             ) -> Result<Self::Path, Self::Error> {
1131                 if trait_ref.is_none() {
1132                     if let ty::Adt(def, substs) = self_ty.kind() {
1133                         return self.print_def_path(def.did(), substs);
1134                     }
1135                 }
1136
1137                 // This shouldn't ever be needed, but just in case:
1138                 with_no_trimmed_paths!({
1139                     Ok(vec![match trait_ref {
1140                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1141                         None => Symbol::intern(&format!("<{}>", self_ty)),
1142                     }])
1143                 })
1144             }
1145
1146             fn path_append_impl(
1147                 self,
1148                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1149                 _disambiguated_data: &DisambiguatedDefPathData,
1150                 self_ty: Ty<'tcx>,
1151                 trait_ref: Option<ty::TraitRef<'tcx>>,
1152             ) -> Result<Self::Path, Self::Error> {
1153                 let mut path = print_prefix(self)?;
1154
1155                 // This shouldn't ever be needed, but just in case:
1156                 path.push(match trait_ref {
1157                     Some(trait_ref) => {
1158                         with_no_trimmed_paths!(Symbol::intern(&format!(
1159                             "<impl {} for {}>",
1160                             trait_ref.print_only_trait_path(),
1161                             self_ty
1162                         )))
1163                     }
1164                     None => {
1165                         with_no_trimmed_paths!(Symbol::intern(&format!("<impl {}>", self_ty)))
1166                     }
1167                 });
1168
1169                 Ok(path)
1170             }
1171
1172             fn path_append(
1173                 self,
1174                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1175                 disambiguated_data: &DisambiguatedDefPathData,
1176             ) -> Result<Self::Path, Self::Error> {
1177                 let mut path = print_prefix(self)?;
1178
1179                 // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1180                 if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1181                     return Ok(path);
1182                 }
1183
1184                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1185                 Ok(path)
1186             }
1187
1188             fn path_generic_args(
1189                 self,
1190                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1191                 _args: &[GenericArg<'tcx>],
1192             ) -> Result<Self::Path, Self::Error> {
1193                 print_prefix(self)
1194             }
1195         }
1196
1197         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1198     }
1199 }
1200
1201 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1202     #[inline]
1203     fn data_layout(&self) -> &abi::TargetDataLayout {
1204         &self.tcx.data_layout
1205     }
1206 }
1207
1208 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1209     #[inline]
1210     fn tcx(&self) -> TyCtxt<'tcx> {
1211         self.tcx
1212     }
1213 }
1214
1215 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1216     #[inline]
1217     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1218         self.param_env
1219     }
1220 }
1221
1222 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1223     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1224
1225     #[inline]
1226     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1227         err
1228     }
1229 }
1230
1231 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1232     match lint_name.split_once("::") {
1233         Some((tool_name, lint_name)) => {
1234             let tool_name = Symbol::intern(tool_name);
1235
1236             (Some(tool_name), lint_name)
1237         }
1238         None => (None, lint_name),
1239     }
1240 }