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 #![deny(rustc::untranslatable_diagnostic)]
  17 #![deny(rustc::diagnostic_outside_of_impl)]
  18
  19 use self::TargetLint::*;
  20
  21 use crate::errors::{
  22     CheckNameDeprecated, CheckNameUnknown, CheckNameUnknownTool, CheckNameWarning, RequestedLevel,
  23     UnsupportedGroup,
  24 };
  25 use crate::levels::LintLevelsBuilder;
  26 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
  27 use rustc_ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
  28 use rustc_data_structures::fx::FxHashMap;
  29 use rustc_data_structures::sync;
  30 use rustc_errors::{add_elided_lifetime_in_path_suggestion, DiagnosticBuilder, DiagnosticMessage};
  31 use rustc_errors::{Applicability, DecorateLint, MultiSpan, SuggestionStyle};
  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::EffectiveVisibilities;
  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 type EarlyLintPassFactory = dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync;
  54 type LateLintPassFactory =
  55     dyn for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx> + sync::Send + sync::Sync;
  56
  57 /// Information about the registered lints.
  58 ///
  59 /// This is basically the subset of `Context` that we can
  60 /// build early in the compile pipeline.
  61 pub struct LintStore {
  62     /// Registered lints.
  63     lints: Vec<&'static Lint>,
  64
  65     /// Constructor functions for each variety of lint pass.
  66     ///
  67     /// These should only be called once, but since we want to avoid locks or
  68     /// interior mutability, we don't enforce this (and lints should, in theory,
  69     /// be compatible with being constructed more than once, though not
  70     /// necessarily in a sane manner. This is safe though.)
  71     pub pre_expansion_passes: Vec<Box<EarlyLintPassFactory>>,
  72     pub early_passes: Vec<Box<EarlyLintPassFactory>>,
  73     pub late_passes: Vec<Box<LateLintPassFactory>>,
  74     /// This is unique in that we construct them per-module, so not once.
  75     pub late_module_passes: Vec<Box<LateLintPassFactory>>,
  76
  77     /// Lints indexed by name.
  78     by_name: FxHashMap<String, TargetLint>,
  79
  80     /// Map of registered lint groups to what lints they expand to.
  81     lint_groups: FxHashMap<&'static str, LintGroup>,
  82 }
  83
  84 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  85 #[derive(Debug)]
  86 enum TargetLint {
  87     /// A direct lint target
  88     Id(LintId),
  89
  90     /// Temporary renaming, used for easing migration pain; see #16545
  91     Renamed(String, LintId),
  92
  93     /// Lint with this name existed previously, but has been removed/deprecated.
  94     /// The string argument is the reason for removal.
  95     Removed(String),
  96
  97     /// A lint name that should give no warnings and have no effect.
  98     ///
  99     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 100     Ignored,
 101 }
 102
 103 pub enum FindLintError {
 104     NotFound,
 105     Removed,
 106 }
 107
 108 struct LintAlias {
 109     name: &'static str,
 110     /// Whether deprecation warnings should be suppressed for this alias.
 111     silent: bool,
 112 }
 113
 114 struct LintGroup {
 115     lint_ids: Vec<LintId>,
 116     from_plugin: bool,
 117     depr: Option<LintAlias>,
 118 }
 119
 120 #[derive(Debug)]
 121 pub enum CheckLintNameResult<'a> {
 122     Ok(&'a [LintId]),
 123     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 124     NoLint(Option<Symbol>),
 125     /// The lint refers to a tool that has not been registered.
 126     NoTool,
 127     /// The lint is either renamed or removed. This is the warning
 128     /// message, and an optional new name (`None` if removed).
 129     Warning(String, Option<String>),
 130     /// The lint is from a tool. If the Option is None, then either
 131     /// the lint does not exist in the tool or the code was not
 132     /// compiled with the tool and therefore the lint was never
 133     /// added to the `LintStore`. Otherwise the `LintId` will be
 134     /// returned as if it where a rustc lint.
 135     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 136 }
 137
 138 impl LintStore {
 139     pub fn new() -> LintStore {
 140         LintStore {
 141             lints: vec![],
 142             pre_expansion_passes: vec![],
 143             early_passes: vec![],
 144             late_passes: vec![],
 145             late_module_passes: vec![],
 146             by_name: Default::default(),
 147             lint_groups: Default::default(),
 148         }
 149     }
 150
 151     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 152         &self.lints
 153     }
 154
 155     pub fn get_lint_groups<'t>(
 156         &'t self,
 157     ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
 158         // This function is not used in a way which observes the order of lints.
 159         #[allow(rustc::potential_query_instability)]
 160         self.lint_groups
 161             .iter()
 162             .filter(|(_, LintGroup { depr, .. })| {
 163                 // Don't display deprecated lint groups.
 164                 depr.is_none()
 165             })
 166             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 167                 (*k, lint_ids.clone(), *from_plugin)
 168             })
 169     }
 170
 171     pub fn register_early_pass(
 172         &mut self,
 173         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 174     ) {
 175         self.early_passes.push(Box::new(pass));
 176     }
 177
 178     /// This lint pass is softly deprecated. It misses expanded code and has caused a few
 179     /// errors in the past. Currently, it is only used in Clippy. New implementations
 180     /// should avoid using this interface, as it might be removed in the future.
 181     ///
 182     /// * See [rust#69838](https://github.com/rust-lang/rust/pull/69838)
 183     /// * See [rust-clippy#5518](https://github.com/rust-lang/rust-clippy/pull/5518)
 184     pub fn register_pre_expansion_pass(
 185         &mut self,
 186         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 187     ) {
 188         self.pre_expansion_passes.push(Box::new(pass));
 189     }
 190
 191     pub fn register_late_pass(
 192         &mut self,
 193         pass: impl for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx>
 194         + 'static
 195         + sync::Send
 196         + sync::Sync,
 197     ) {
 198         self.late_passes.push(Box::new(pass));
 199     }
 200
 201     pub fn register_late_mod_pass(
 202         &mut self,
 203         pass: impl for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx>
 204         + 'static
 205         + sync::Send
 206         + sync::Sync,
 207     ) {
 208         self.late_module_passes.push(Box::new(pass));
 209     }
 210
 211     /// Helper method for register_early/late_pass
 212     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 213         for lint in lints {
 214             self.lints.push(lint);
 215
 216             let id = LintId::of(lint);
 217             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 218                 bug!("duplicate specification of lint {}", lint.name_lower())
 219             }
 220
 221             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 222                 if let Some(edition) = reason.edition() {
 223                     self.lint_groups
 224                         .entry(edition.lint_name())
 225                         .or_insert(LintGroup {
 226                             lint_ids: vec![],
 227                             from_plugin: lint.is_plugin,
 228                             depr: None,
 229                         })
 230                         .lint_ids
 231                         .push(id);
 232                 } else {
 233                     // Lints belonging to the `future_incompatible` lint group are lints where a
 234                     // future version of rustc will cause existing code to stop compiling.
 235                     // Lints tied to an edition don't count because they are opt-in.
 236                     self.lint_groups
 237                         .entry("future_incompatible")
 238                         .or_insert(LintGroup {
 239                             lint_ids: vec![],
 240                             from_plugin: lint.is_plugin,
 241                             depr: None,
 242                         })
 243                         .lint_ids
 244                         .push(id);
 245                 }
 246             }
 247         }
 248     }
 249
 250     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 251         self.lint_groups.insert(
 252             alias,
 253             LintGroup {
 254                 lint_ids: vec![],
 255                 from_plugin: false,
 256                 depr: Some(LintAlias { name: lint_name, silent: true }),
 257             },
 258         );
 259     }
 260
 261     pub fn register_group(
 262         &mut self,
 263         from_plugin: bool,
 264         name: &'static str,
 265         deprecated_name: Option<&'static str>,
 266         to: Vec<LintId>,
 267     ) {
 268         let new = self
 269             .lint_groups
 270             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 271             .is_none();
 272         if let Some(deprecated) = deprecated_name {
 273             self.lint_groups.insert(
 274                 deprecated,
 275                 LintGroup {
 276                     lint_ids: vec![],
 277                     from_plugin,
 278                     depr: Some(LintAlias { name, silent: false }),
 279                 },
 280             );
 281         }
 282
 283         if !new {
 284             bug!("duplicate specification of lint group {}", name);
 285         }
 286     }
 287
 288     /// This lint should give no warning and have no effect.
 289     ///
 290     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 291     #[track_caller]
 292     pub fn register_ignored(&mut self, name: &str) {
 293         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 294             bug!("duplicate specification of lint {}", name);
 295         }
 296     }
 297
 298     /// This lint has been renamed; warn about using the new name and apply the lint.
 299     #[track_caller]
 300     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 301         let Some(&Id(target)) = self.by_name.get(new_name) else {
 302             bug!("invalid lint renaming of {} to {}", old_name, new_name);
 303         };
 304         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 305     }
 306
 307     pub fn register_removed(&mut self, name: &str, reason: &str) {
 308         self.by_name.insert(name.into(), Removed(reason.into()));
 309     }
 310
 311     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 312         match self.by_name.get(lint_name) {
 313             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 314             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 315             Some(&Removed(_)) => Err(FindLintError::Removed),
 316             Some(&Ignored) => Ok(vec![]),
 317             None => loop {
 318                 return match self.lint_groups.get(lint_name) {
 319                     Some(LintGroup { lint_ids, depr, .. }) => {
 320                         if let Some(LintAlias { name, .. }) = depr {
 321                             lint_name = name;
 322                             continue;
 323                         }
 324                         Ok(lint_ids.clone())
 325                     }
 326                     None => Err(FindLintError::Removed),
 327                 };
 328             },
 329         }
 330     }
 331
 332     /// Checks the validity of lint names derived from the command line.
 333     pub fn check_lint_name_cmdline(
 334         &self,
 335         sess: &Session,
 336         lint_name: &str,
 337         level: Level,
 338         registered_tools: &RegisteredTools,
 339     ) {
 340         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 341         if lint_name_only == crate::WARNINGS.name_lower() && matches!(level, Level::ForceWarn(_)) {
 342             sess.emit_err(UnsupportedGroup { lint_group: crate::WARNINGS.name_lower() });
 343             return;
 344         }
 345         let lint_name = lint_name.to_string();
 346         match self.check_lint_name(lint_name_only, tool_name, registered_tools) {
 347             CheckLintNameResult::Warning(msg, _) => {
 348                 sess.emit_warning(CheckNameWarning {
 349                     msg,
 350                     sub: RequestedLevel { level, lint_name },
 351                 });
 352             }
 353             CheckLintNameResult::NoLint(suggestion) => {
 354                 sess.emit_err(CheckNameUnknown {
 355                     lint_name: lint_name.clone(),
 356                     suggestion,
 357                     sub: RequestedLevel { level, lint_name },
 358                 });
 359             }
 360             CheckLintNameResult::Tool(Err((Some(_), new_name))) => {
 361                 sess.emit_warning(CheckNameDeprecated {
 362                     lint_name: lint_name.clone(),
 363                     new_name,
 364                     sub: RequestedLevel { level, lint_name },
 365                 });
 366             }
 367             CheckLintNameResult::NoTool => {
 368                 sess.emit_err(CheckNameUnknownTool {
 369                     tool_name: tool_name.unwrap(),
 370                     sub: RequestedLevel { level, lint_name },
 371                 });
 372             }
 373             _ => {}
 374         };
 375     }
 376
 377     /// True if this symbol represents a lint group name.
 378     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 379         debug!(
 380             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 381             lint_name,
 382             self.lint_groups.keys().collect::<Vec<_>>()
 383         );
 384         let lint_name_str = lint_name.as_str();
 385         self.lint_groups.contains_key(lint_name_str) || {
 386             let warnings_name_str = crate::WARNINGS.name_lower();
 387             lint_name_str == warnings_name_str
 388         }
 389     }
 390
 391     /// Checks the name of a lint for its existence, and whether it was
 392     /// renamed or removed. Generates a DiagnosticBuilder containing a
 393     /// warning for renamed and removed lints. This is over both lint
 394     /// names from attributes and those passed on the command line. Since
 395     /// it emits non-fatal warnings and there are *two* lint passes that
 396     /// inspect attributes, this is only run from the late pass to avoid
 397     /// printing duplicate warnings.
 398     pub fn check_lint_name(
 399         &self,
 400         lint_name: &str,
 401         tool_name: Option<Symbol>,
 402         registered_tools: &RegisteredTools,
 403     ) -> CheckLintNameResult<'_> {
 404         if let Some(tool_name) = tool_name {
 405             // FIXME: rustc and rustdoc are considered tools for lints, but not for attributes.
 406             if tool_name != sym::rustc
 407                 && tool_name != sym::rustdoc
 408                 && !registered_tools.contains(&Ident::with_dummy_span(tool_name))
 409             {
 410                 return CheckLintNameResult::NoTool;
 411             }
 412         }
 413
 414         let complete_name = if let Some(tool_name) = tool_name {
 415             format!("{}::{}", tool_name, lint_name)
 416         } else {
 417             lint_name.to_string()
 418         };
 419         // If the lint was scoped with `tool::` check if the tool lint exists
 420         if let Some(tool_name) = tool_name {
 421             match self.by_name.get(&complete_name) {
 422                 None => match self.lint_groups.get(&*complete_name) {
 423                     // If the lint isn't registered, there are two possibilities:
 424                     None => {
 425                         // 1. The tool is currently running, so this lint really doesn't exist.
 426                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 427                         debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 428                         let tool_prefix = format!("{}::", tool_name);
 429                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 430                             self.no_lint_suggestion(&complete_name)
 431                         } else {
 432                             // 2. The tool isn't currently running, so no lints will be registered.
 433                             // To avoid giving a false positive, ignore all unknown lints.
 434                             CheckLintNameResult::Tool(Err((None, String::new())))
 435                         };
 436                     }
 437                     Some(LintGroup { lint_ids, .. }) => {
 438                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 439                     }
 440                 },
 441                 Some(Id(id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 442                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 443                 // to treat tool_lints and rustc lints different and can use the code below.
 444                 _ => {}
 445             }
 446         }
 447         match self.by_name.get(&complete_name) {
 448             Some(Renamed(new_name, _)) => CheckLintNameResult::Warning(
 449                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 450                 Some(new_name.to_owned()),
 451             ),
 452             Some(Removed(reason)) => CheckLintNameResult::Warning(
 453                 format!("lint `{}` has been removed: {}", complete_name, reason),
 454                 None,
 455             ),
 456             None => match self.lint_groups.get(&*complete_name) {
 457                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 458                 // variant of this lint
 459                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 460                 Some(LintGroup { lint_ids, depr, .. }) => {
 461                     // Check if the lint group name is deprecated
 462                     if let Some(LintAlias { name, silent }) = depr {
 463                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 464                         return if *silent {
 465                             CheckLintNameResult::Ok(&lint_ids)
 466                         } else {
 467                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 468                         };
 469                     }
 470                     CheckLintNameResult::Ok(&lint_ids)
 471                 }
 472             },
 473             Some(Id(id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 474             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 475         }
 476     }
 477
 478     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 479         let name_lower = lint_name.to_lowercase();
 480
 481         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 482             // First check if the lint name is (partly) in upper case instead of lower case...
 483             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 484         }
 485         // ...if not, search for lints with a similar name
 486         // Note: find_best_match_for_name depends on the sort order of its input vector.
 487         // To ensure deterministic output, sort elements of the lint_groups hash map.
 488         // Also, never suggest deprecated lint groups.
 489         let mut groups: Vec<_> = self
 490             .lint_groups
 491             .iter()
 492             .filter_map(|(k, LintGroup { depr, .. })| if depr.is_none() { Some(k) } else { None })
 493             .collect();
 494         groups.sort();
 495         let groups = groups.iter().map(|k| Symbol::intern(k));
 496         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 497         let names: Vec<Symbol> = groups.chain(lints).collect();
 498         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 499         CheckLintNameResult::NoLint(suggestion)
 500     }
 501
 502     fn check_tool_name_for_backwards_compat(
 503         &self,
 504         lint_name: &str,
 505         tool_name: &str,
 506     ) -> CheckLintNameResult<'_> {
 507         let complete_name = format!("{}::{}", tool_name, lint_name);
 508         match self.by_name.get(&complete_name) {
 509             None => match self.lint_groups.get(&*complete_name) {
 510                 // Now we are sure, that this lint exists nowhere
 511                 None => self.no_lint_suggestion(lint_name),
 512                 Some(LintGroup { lint_ids, depr, .. }) => {
 513                     // Reaching this would be weird, but let's cover this case anyway
 514                     if let Some(LintAlias { name, silent }) = depr {
 515                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 516                         return if *silent {
 517                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 518                         } else {
 519                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 520                         };
 521                     }
 522                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 523                 }
 524             },
 525             Some(Id(id)) => {
 526                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 527             }
 528             Some(other) => {
 529                 debug!("got renamed lint {:?}", other);
 530                 CheckLintNameResult::NoLint(None)
 531             }
 532         }
 533     }
 534 }
 535
 536 /// Context for lint checking outside of type inference.
 537 pub struct LateContext<'tcx> {
 538     /// Type context we're checking in.
 539     pub tcx: TyCtxt<'tcx>,
 540
 541     /// Current body, or `None` if outside a body.
 542     pub enclosing_body: Option<hir::BodyId>,
 543
 544     /// Type-checking results for the current body. Access using the `typeck_results`
 545     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 546     // FIXME(eddyb) move all the code accessing internal fields like this,
 547     // to this module, to avoid exposing it to lint logic.
 548     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 549
 550     /// Parameter environment for the item we are in.
 551     pub param_env: ty::ParamEnv<'tcx>,
 552
 553     /// Items accessible from the crate being checked.
 554     pub effective_visibilities: &'tcx EffectiveVisibilities,
 555
 556     /// The store of registered lints and the lint levels.
 557     pub lint_store: &'tcx LintStore,
 558
 559     pub last_node_with_lint_attrs: hir::HirId,
 560
 561     /// Generic type parameters in scope for the item we are in.
 562     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 563
 564     /// We are only looking at one module
 565     pub only_module: bool,
 566 }
 567
 568 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 569 pub struct EarlyContext<'a> {
 570     pub builder: LintLevelsBuilder<'a, crate::levels::TopDown>,
 571     pub buffered: LintBuffer,
 572 }
 573
 574 pub trait LintPassObject: Sized {}
 575
 576 impl LintPassObject for EarlyLintPassObject {}
 577
 578 impl LintPassObject for LateLintPassObject<'_> {}
 579
 580 pub trait LintContext: Sized {
 581     type PassObject: LintPassObject;
 582
 583     fn sess(&self) -> &Session;
 584     fn lints(&self) -> &LintStore;
 585
 586     /// Emit a lint at the appropriate level, with an optional associated span and an existing diagnostic.
 587     ///
 588     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 589     ///
 590     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 591     #[rustc_lint_diagnostics]
 592     fn lookup_with_diagnostics(
 593         &self,
 594         lint: &'static Lint,
 595         span: Option<impl Into<MultiSpan>>,
 596         msg: impl Into<DiagnosticMessage>,
 597         decorate: impl for<'a, 'b> FnOnce(
 598             &'b mut DiagnosticBuilder<'a, ()>,
 599         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 600         diagnostic: BuiltinLintDiagnostics,
 601     ) {
 602         // We first generate a blank diagnostic.
 603         self.lookup(lint, span, msg,|db| {
 604             // Now, set up surrounding context.
 605             let sess = self.sess();
 606             match diagnostic {
 607                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
 608                     let spans: Vec<_> = content
 609                         .char_indices()
 610                         .filter_map(|(i, c)| {
 611                             TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
 612                                 let lo = span.lo() + BytePos(2 + i as u32);
 613                                 (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
 614                             })
 615                         })
 616                         .collect();
 617                     let (an, s) = match spans.len() {
 618                         1 => ("an ", ""),
 619                         _ => ("", "s"),
 620                     };
 621                     db.span_label(span, &format!(
 622                         "this comment contains {}invisible unicode text flow control codepoint{}",
 623                         an,
 624                         s,
 625                     ));
 626                     for (c, span) in &spans {
 627                         db.span_label(*span, format!("{:?}", c));
 628                     }
 629                     db.note(
 630                         "these kind of unicode codepoints change the way text flows on \
 631                          applications that support them, but can cause confusion because they \
 632                          change the order of characters on the screen",
 633                     );
 634                     if !spans.is_empty() {
 635                         db.multipart_suggestion_with_style(
 636                             "if their presence wasn't intentional, you can remove them",
 637                             spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
 638                             Applicability::MachineApplicable,
 639                             SuggestionStyle::HideCodeAlways,
 640                         );
 641                     }
 642                 },
 643                 BuiltinLintDiagnostics::Normal => (),
 644                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 645                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 646                         Ok(ref s) => {
 647                             // FIXME(Manishearth) ideally the emitting code
 648                             // can tell us whether or not this is global
 649                             let opt_colon =
 650                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 651
 652                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 653                         }
 654                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 655                     };
 656                     db.span_suggestion(span, "use `crate`", sugg, app);
 657                 }
 658                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 659                     db.span_label(
 660                         span,
 661                         "names from parent modules are not accessible without an explicit import",
 662                     );
 663                 }
 664                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 665                     span_def,
 666                 ) => {
 667                     db.span_note(span_def, "the macro is defined here");
 668                 }
 669                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 670                     n,
 671                     path_span,
 672                     incl_angl_brckt,
 673                     insertion_span,
 674                 ) => {
 675                     add_elided_lifetime_in_path_suggestion(
 676                         sess.source_map(),
 677                         db,
 678                         n,
 679                         path_span,
 680                         incl_angl_brckt,
 681                         insertion_span,
 682                     );
 683                 }
 684                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 685                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 686                 }
 687                 BuiltinLintDiagnostics::UnusedImports(message, replaces, in_test_module) => {
 688                     if !replaces.is_empty() {
 689                         db.tool_only_multipart_suggestion(
 690                             &message,
 691                             replaces,
 692                             Applicability::MachineApplicable,
 693                         );
 694                     }
 695
 696                     if let Some(span) = in_test_module {
 697                         db.span_help(
 698                             self.sess().source_map().guess_head_span(span),
 699                             "consider adding a `#[cfg(test)]` to the containing module",
 700                         );
 701                     }
 702                 }
 703                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 704                     for (span, is_imported) in spans {
 705                         let introduced = if is_imported { "imported" } else { "defined" };
 706                         db.span_label(
 707                             span,
 708                             format!("the item `{}` is already {} here", ident, introduced),
 709                         );
 710                     }
 711                 }
 712                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 713                     stability::deprecation_suggestion(db, "macro", suggestion, span)
 714                 }
 715                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 716                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 717                     db.help("to document an item produced by a macro, \
 718                                   the macro must produce the documentation as part of its expansion");
 719                 }
 720                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 721                     db.span_suggestion(span, "remove `mut` from the parameter", ident, Applicability::MachineApplicable);
 722                 }
 723                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 724                     db.span_label(span, "ABI should be specified here");
 725                     db.help(&format!("the default ABI is {}", default_abi.name()));
 726                 }
 727                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 728                     db.span_label(span, "the attribute is introduced here");
 729                 }
 730                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 731                     db.note(&note);
 732                 }
 733                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 734                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 735                 }
 736                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 737                     db.span_label(span, "unknown prefix");
 738                     db.span_suggestion_verbose(
 739                         span.shrink_to_hi(),
 740                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 741                         " ",
 742                         Applicability::MachineApplicable,
 743                     );
 744                 }
 745                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 746                     attr_name,
 747                     macro_name,
 748                     invoc_span
 749                 } => {
 750                     db.span_note(
 751                         invoc_span,
 752                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 753                     );
 754                 }
 755                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 756                     if is_trailing {
 757                         db.note("macro invocations at the end of a block are treated as expressions");
 758                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 759                     }
 760                 }
 761                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 762                     db.multipart_suggestion(
 763                         "wrap this expression in parentheses",
 764                         vec![(span.shrink_to_lo(), "(".to_string()),
 765                              (span.shrink_to_hi(), ")".to_string())],
 766                         Applicability::MachineApplicable
 767                     );
 768                 }
 769                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 770                     db.help(&help);
 771                     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");
 772                 },
 773                 BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), None) => {
 774                     let Some(names_valid) = &sess.parse_sess.check_config.names_valid else {
 775                         bug!("it shouldn't be possible to have a diagnostic on a name if name checking is not enabled");
 776                     };
 777                     let possibilities: Vec<Symbol> = names_valid.iter().map(|s| *s).collect();
 778
 779                     // Suggest the most probable if we found one
 780                     if let Some(best_match) = find_best_match_for_name(&possibilities, name, None) {
 781                         db.span_suggestion(name_span, "did you mean", best_match, Applicability::MaybeIncorrect);
 782                     }
 783                 },
 784                 BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), Some((value, value_span))) => {
 785                     let Some(values) = &sess.parse_sess.check_config.values_valid.get(&name) else {
 786                         bug!("it shouldn't be possible to have a diagnostic on a value whose name is not in values");
 787                     };
 788                     let possibilities: Vec<Symbol> = values.iter().map(|&s| s).collect();
 789
 790                     // Show the full list if all possible values for a given name, but don't do it
 791                     // for names as the possibilities could be very long
 792                     if !possibilities.is_empty() {
 793                         {
 794                             let mut possibilities = possibilities.iter().map(Symbol::as_str).collect::<Vec<_>>();
 795                             possibilities.sort();
 796
 797                             let possibilities = possibilities.join(", ");
 798                             db.note(&format!("expected values for `{name}` are: {possibilities}"));
 799                         }
 800
 801                         // Suggest the most probable if we found one
 802                         if let Some(best_match) = find_best_match_for_name(&possibilities, value, None) {
 803                             db.span_suggestion(value_span, "did you mean", format!("\"{best_match}\""), Applicability::MaybeIncorrect);
 804                         }
 805                     } else {
 806                         db.note(&format!("no expected value for `{name}`"));
 807                         if name != sym::feature {
 808                             db.span_suggestion(name_span.shrink_to_hi().to(value_span), "remove the value", "", Applicability::MaybeIncorrect);
 809                         }
 810                     }
 811                 },
 812                 BuiltinLintDiagnostics::DeprecatedWhereclauseLocation(new_span, suggestion) => {
 813                     db.multipart_suggestion(
 814                         "move it to the end of the type declaration",
 815                         vec![(db.span.primary_span().unwrap(), "".to_string()), (new_span, suggestion)],
 816                         Applicability::MachineApplicable,
 817                     );
 818                     db.note(
 819                         "see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information",
 820                     );
 821                 },
 822                 BuiltinLintDiagnostics::SingleUseLifetime {
 823                     param_span,
 824                     use_span: Some((use_span, elide)),
 825                     deletion_span,
 826                 } => {
 827                     debug!(?param_span, ?use_span, ?deletion_span);
 828                     db.span_label(param_span, "this lifetime...");
 829                     db.span_label(use_span, "...is used only here");
 830                     let msg = "elide the single-use lifetime";
 831                     let (use_span, replace_lt) = if elide {
 832                         let use_span = sess.source_map().span_extend_while(
 833                             use_span,
 834                             char::is_whitespace,
 835                         ).unwrap_or(use_span);
 836                         (use_span, String::new())
 837                     } else {
 838                         (use_span, "'_".to_owned())
 839                     };
 840                     db.multipart_suggestion(
 841                         msg,
 842                         vec![(deletion_span, String::new()), (use_span, replace_lt)],
 843                         Applicability::MachineApplicable,
 844                     );
 845                 },
 846                 BuiltinLintDiagnostics::SingleUseLifetime {
 847                     param_span: _,
 848                     use_span: None,
 849                     deletion_span,
 850                 } => {
 851                     debug!(?deletion_span);
 852                     db.span_suggestion(
 853                         deletion_span,
 854                         "elide the unused lifetime",
 855                         "",
 856                         Applicability::MachineApplicable,
 857                     );
 858                 },
 859                 BuiltinLintDiagnostics::NamedArgumentUsedPositionally{ position_sp_to_replace, position_sp_for_msg, named_arg_sp, named_arg_name, is_formatting_arg} => {
 860                     db.span_label(named_arg_sp, "this named argument is referred to by position in formatting string");
 861                     if let Some(positional_arg_for_msg) = position_sp_for_msg {
 862                         let msg = format!("this formatting argument uses named argument `{}` by position", named_arg_name);
 863                         db.span_label(positional_arg_for_msg, msg);
 864                     }
 865
 866                     if let Some(positional_arg_to_replace) = position_sp_to_replace {
 867                         let name = if is_formatting_arg { named_arg_name + "$" } else { named_arg_name };
 868                         let span_to_replace = if let Ok(positional_arg_content) =
 869                             self.sess().source_map().span_to_snippet(positional_arg_to_replace) && positional_arg_content.starts_with(':') {
 870                             positional_arg_to_replace.shrink_to_lo()
 871                         } else {
 872                             positional_arg_to_replace
 873                         };
 874                         db.span_suggestion_verbose(
 875                             span_to_replace,
 876                             "use the named argument by name to avoid ambiguity",
 877                             name,
 878                             Applicability::MaybeIncorrect,
 879                         );
 880                     }
 881                 }
 882             }
 883             // Rewrap `db`, and pass control to the user.
 884             decorate(db)
 885         });
 886     }
 887
 888     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 889     // set the span in their `decorate` function (preferably using set_span).
 890     /// Emit a lint at the appropriate level, with an optional associated span.
 891     ///
 892     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 893     ///
 894     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 895     #[rustc_lint_diagnostics]
 896     fn lookup<S: Into<MultiSpan>>(
 897         &self,
 898         lint: &'static Lint,
 899         span: Option<S>,
 900         msg: impl Into<DiagnosticMessage>,
 901         decorate: impl for<'a, 'b> FnOnce(
 902             &'b mut DiagnosticBuilder<'a, ()>,
 903         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 904     );
 905
 906     /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
 907     /// typically generated by `#[derive(LintDiagnostic)]`).
 908     fn emit_spanned_lint<S: Into<MultiSpan>>(
 909         &self,
 910         lint: &'static Lint,
 911         span: S,
 912         decorator: impl for<'a> DecorateLint<'a, ()>,
 913     ) {
 914         self.lookup(lint, Some(span), decorator.msg(), |diag| decorator.decorate_lint(diag));
 915     }
 916
 917     /// Emit a lint at the appropriate level, with an associated span.
 918     ///
 919     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 920     ///
 921     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 922     #[rustc_lint_diagnostics]
 923     fn struct_span_lint<S: Into<MultiSpan>>(
 924         &self,
 925         lint: &'static Lint,
 926         span: S,
 927         msg: impl Into<DiagnosticMessage>,
 928         decorate: impl for<'a, 'b> FnOnce(
 929             &'b mut DiagnosticBuilder<'a, ()>,
 930         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 931     ) {
 932         self.lookup(lint, Some(span), msg, decorate);
 933     }
 934
 935     /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
 936     /// generated by `#[derive(LintDiagnostic)]`).
 937     fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
 938         self.lookup(lint, None as Option<Span>, decorator.msg(), |diag| {
 939             decorator.decorate_lint(diag)
 940         });
 941     }
 942
 943     /// Emit a lint at the appropriate level, with no associated span.
 944     ///
 945     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 946     ///
 947     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 948     #[rustc_lint_diagnostics]
 949     fn lint(
 950         &self,
 951         lint: &'static Lint,
 952         msg: impl Into<DiagnosticMessage>,
 953         decorate: impl for<'a, 'b> FnOnce(
 954             &'b mut DiagnosticBuilder<'a, ()>,
 955         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 956     ) {
 957         self.lookup(lint, None as Option<Span>, msg, decorate);
 958     }
 959
 960     /// This returns the lint level for the given lint at the current location.
 961     fn get_lint_level(&self, lint: &'static Lint) -> Level;
 962
 963     /// This function can be used to manually fulfill an expectation. This can
 964     /// be used for lints which contain several spans, and should be suppressed,
 965     /// if either location was marked with an expectation.
 966     ///
 967     /// Note that this function should only be called for [`LintExpectationId`]s
 968     /// retrieved from the current lint pass. Buffered or manually created ids can
 969     /// cause ICEs.
 970     #[rustc_lint_diagnostics]
 971     fn fulfill_expectation(&self, expectation: LintExpectationId) {
 972         // We need to make sure that submitted expectation ids are correctly fulfilled suppressed
 973         // and stored between compilation sessions. To not manually do these steps, we simply create
 974         // a dummy diagnostic and emit is as usual, which will be suppressed and stored like a normal
 975         // expected lint diagnostic.
 976         self.sess()
 977             .struct_expect(
 978                 "this is a dummy diagnostic, to submit and store an expectation",
 979                 expectation,
 980             )
 981             .emit();
 982     }
 983 }
 984
 985 impl<'a> EarlyContext<'a> {
 986     pub(crate) fn new(
 987         sess: &'a Session,
 988         warn_about_weird_lints: bool,
 989         lint_store: &'a LintStore,
 990         registered_tools: &'a RegisteredTools,
 991         buffered: LintBuffer,
 992     ) -> EarlyContext<'a> {
 993         EarlyContext {
 994             builder: LintLevelsBuilder::new(
 995                 sess,
 996                 warn_about_weird_lints,
 997                 lint_store,
 998                 registered_tools,
 999             ),
1000             buffered,
1001         }
1002     }
1003 }
1004
1005 impl<'tcx> LintContext for LateContext<'tcx> {
1006     type PassObject = LateLintPassObject<'tcx>;
1007
1008     /// Gets the overall compiler `Session` object.
1009     fn sess(&self) -> &Session {
1010         &self.tcx.sess
1011     }
1012
1013     fn lints(&self) -> &LintStore {
1014         &*self.lint_store
1015     }
1016
1017     #[rustc_lint_diagnostics]
1018     fn lookup<S: Into<MultiSpan>>(
1019         &self,
1020         lint: &'static Lint,
1021         span: Option<S>,
1022         msg: impl Into<DiagnosticMessage>,
1023         decorate: impl for<'a, 'b> FnOnce(
1024             &'b mut DiagnosticBuilder<'a, ()>,
1025         ) -> &'b mut DiagnosticBuilder<'a, ()>,
1026     ) {
1027         let hir_id = self.last_node_with_lint_attrs;
1028
1029         match span {
1030             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, msg, decorate),
1031             None => self.tcx.struct_lint_node(lint, hir_id, msg, decorate),
1032         }
1033     }
1034
1035     fn get_lint_level(&self, lint: &'static Lint) -> Level {
1036         self.tcx.lint_level_at_node(lint, self.last_node_with_lint_attrs).0
1037     }
1038 }
1039
1040 impl LintContext for EarlyContext<'_> {
1041     type PassObject = EarlyLintPassObject;
1042
1043     /// Gets the overall compiler `Session` object.
1044     fn sess(&self) -> &Session {
1045         &self.builder.sess()
1046     }
1047
1048     fn lints(&self) -> &LintStore {
1049         self.builder.lint_store()
1050     }
1051
1052     #[rustc_lint_diagnostics]
1053     fn lookup<S: Into<MultiSpan>>(
1054         &self,
1055         lint: &'static Lint,
1056         span: Option<S>,
1057         msg: impl Into<DiagnosticMessage>,
1058         decorate: impl for<'a, 'b> FnOnce(
1059             &'b mut DiagnosticBuilder<'a, ()>,
1060         ) -> &'b mut DiagnosticBuilder<'a, ()>,
1061     ) {
1062         self.builder.struct_lint(lint, span.map(|s| s.into()), msg, decorate)
1063     }
1064
1065     fn get_lint_level(&self, lint: &'static Lint) -> Level {
1066         self.builder.lint_level(lint).0
1067     }
1068 }
1069
1070 impl<'tcx> LateContext<'tcx> {
1071     /// Gets the type-checking results for the current body,
1072     /// or `None` if outside a body.
1073     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
1074         self.cached_typeck_results.get().or_else(|| {
1075             self.enclosing_body.map(|body| {
1076                 let typeck_results = self.tcx.typeck_body(body);
1077                 self.cached_typeck_results.set(Some(typeck_results));
1078                 typeck_results
1079             })
1080         })
1081     }
1082
1083     /// Gets the type-checking results for the current body.
1084     /// As this will ICE if called outside bodies, only call when working with
1085     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
1086     #[track_caller]
1087     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
1088         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
1089     }
1090
1091     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
1092     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
1093     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
1094     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
1095         match *qpath {
1096             hir::QPath::Resolved(_, ref path) => path.res,
1097             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
1098                 .maybe_typeck_results()
1099                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
1100                 .or_else(|| {
1101                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
1102                         Some(self.tcx.typeck(id.owner.def_id))
1103                     } else {
1104                         None
1105                     }
1106                 })
1107                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
1108                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
1109         }
1110     }
1111
1112     /// Check if a `DefId`'s path matches the given absolute type path usage.
1113     ///
1114     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
1115     /// inherent `impl` blocks are matched with the name of the type.
1116     ///
1117     /// Instead of using this method, it is often preferable to instead use
1118     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
1119     /// as paths get invalidated if the target definition moves.
1120     ///
1121     /// # Examples
1122     ///
1123     /// ```rust,ignore (no context or def id available)
1124     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
1125     ///     // The given `def_id` is that of an `Option` type
1126     /// }
1127     /// ```
1128     ///
1129     /// Used by clippy, but should be replaced by diagnostic items eventually.
1130     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
1131         let names = self.get_def_path(def_id);
1132
1133         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
1134     }
1135
1136     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
1137     ///
1138     /// # Examples
1139     ///
1140     /// ```rust,ignore (no context or def id available)
1141     /// let def_path = cx.get_def_path(def_id);
1142     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
1143     ///     // The given `def_id` is that of an `Option` type
1144     /// }
1145     /// ```
1146     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
1147         pub struct AbsolutePathPrinter<'tcx> {
1148             pub tcx: TyCtxt<'tcx>,
1149         }
1150
1151         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
1152             type Error = !;
1153
1154             type Path = Vec<Symbol>;
1155             type Region = ();
1156             type Type = ();
1157             type DynExistential = ();
1158             type Const = ();
1159
1160             fn tcx(&self) -> TyCtxt<'tcx> {
1161                 self.tcx
1162             }
1163
1164             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
1165                 Ok(())
1166             }
1167
1168             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
1169                 Ok(())
1170             }
1171
1172             fn print_dyn_existential(
1173                 self,
1174                 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
1175             ) -> Result<Self::DynExistential, Self::Error> {
1176                 Ok(())
1177             }
1178
1179             fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1180                 Ok(())
1181             }
1182
1183             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1184                 Ok(vec![self.tcx.crate_name(cnum)])
1185             }
1186
1187             fn path_qualified(
1188                 self,
1189                 self_ty: Ty<'tcx>,
1190                 trait_ref: Option<ty::TraitRef<'tcx>>,
1191             ) -> Result<Self::Path, Self::Error> {
1192                 if trait_ref.is_none() {
1193                     if let ty::Adt(def, substs) = self_ty.kind() {
1194                         return self.print_def_path(def.did(), substs);
1195                     }
1196                 }
1197
1198                 // This shouldn't ever be needed, but just in case:
1199                 with_no_trimmed_paths!({
1200                     Ok(vec![match trait_ref {
1201                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1202                         None => Symbol::intern(&format!("<{}>", self_ty)),
1203                     }])
1204                 })
1205             }
1206
1207             fn path_append_impl(
1208                 self,
1209                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1210                 _disambiguated_data: &DisambiguatedDefPathData,
1211                 self_ty: Ty<'tcx>,
1212                 trait_ref: Option<ty::TraitRef<'tcx>>,
1213             ) -> Result<Self::Path, Self::Error> {
1214                 let mut path = print_prefix(self)?;
1215
1216                 // This shouldn't ever be needed, but just in case:
1217                 path.push(match trait_ref {
1218                     Some(trait_ref) => {
1219                         with_no_trimmed_paths!(Symbol::intern(&format!(
1220                             "<impl {} for {}>",
1221                             trait_ref.print_only_trait_path(),
1222                             self_ty
1223                         )))
1224                     }
1225                     None => {
1226                         with_no_trimmed_paths!(Symbol::intern(&format!("<impl {}>", self_ty)))
1227                     }
1228                 });
1229
1230                 Ok(path)
1231             }
1232
1233             fn path_append(
1234                 self,
1235                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1236                 disambiguated_data: &DisambiguatedDefPathData,
1237             ) -> Result<Self::Path, Self::Error> {
1238                 let mut path = print_prefix(self)?;
1239
1240                 // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1241                 if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1242                     return Ok(path);
1243                 }
1244
1245                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1246                 Ok(path)
1247             }
1248
1249             fn path_generic_args(
1250                 self,
1251                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1252                 _args: &[GenericArg<'tcx>],
1253             ) -> Result<Self::Path, Self::Error> {
1254                 print_prefix(self)
1255             }
1256         }
1257
1258         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1259     }
1260
1261     /// Returns the associated type `name` for `self_ty` as an implementation of `trait_id`.
1262     /// Do not invoke without first verifying that the type implements the trait.
1263     pub fn get_associated_type(
1264         &self,
1265         self_ty: Ty<'tcx>,
1266         trait_id: DefId,
1267         name: &str,
1268     ) -> Option<Ty<'tcx>> {
1269         let tcx = self.tcx;
1270         tcx.associated_items(trait_id)
1271             .find_by_name_and_kind(tcx, Ident::from_str(name), ty::AssocKind::Type, trait_id)
1272             .and_then(|assoc| {
1273                 let proj = tcx.mk_projection(assoc.def_id, [self_ty]);
1274                 tcx.try_normalize_erasing_regions(self.param_env, proj).ok()
1275             })
1276     }
1277 }
1278
1279 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1280     #[inline]
1281     fn data_layout(&self) -> &abi::TargetDataLayout {
1282         &self.tcx.data_layout
1283     }
1284 }
1285
1286 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1287     #[inline]
1288     fn tcx(&self) -> TyCtxt<'tcx> {
1289         self.tcx
1290     }
1291 }
1292
1293 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1294     #[inline]
1295     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1296         self.param_env
1297     }
1298 }
1299
1300 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1301     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1302
1303     #[inline]
1304     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1305         err
1306     }
1307 }
1308
1309 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1310     match lint_name.split_once("::") {
1311         Some((tool_name, lint_name)) => {
1312             let tool_name = Symbol::intern(tool_name);
1313
1314             (Some(tool_name), lint_name)
1315         }
1316         None => (None, lint_name),
1317     }
1318 }