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, DiagnosticBuilder, DiagnosticMessage};
  29 use rustc_errors::{Applicability, DecorateLint, MultiSpan, SuggestionStyle};
  30 use rustc_hir as hir;
  31 use rustc_hir::def::Res;
  32 use rustc_hir::def_id::{CrateNum, DefId};
  33 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  34 use rustc_middle::middle::privacy::EffectiveVisibilities;
  35 use rustc_middle::middle::stability;
  36 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  37 use rustc_middle::ty::print::with_no_trimmed_paths;
  38 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
  39 use rustc_session::lint::{BuiltinLintDiagnostics, LintExpectationId};
  40 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  41 use rustc_session::Session;
  42 use rustc_span::lev_distance::find_best_match_for_name;
  43 use rustc_span::symbol::{sym, Ident, Symbol};
  44 use rustc_span::{BytePos, Span};
  45 use rustc_target::abi;
  46
  47 use std::cell::Cell;
  48 use std::iter;
  49 use std::slice;
  50
  51 type EarlyLintPassFactory = dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync;
  52 type LateLintPassFactory =
  53     dyn for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx> + sync::Send + sync::Sync;
  54
  55 /// Information about the registered lints.
  56 ///
  57 /// This is basically the subset of `Context` that we can
  58 /// build early in the compile pipeline.
  59 pub struct LintStore {
  60     /// Registered lints.
  61     lints: Vec<&'static Lint>,
  62
  63     /// Constructor functions for each variety of lint pass.
  64     ///
  65     /// These should only be called once, but since we want to avoid locks or
  66     /// interior mutability, we don't enforce this (and lints should, in theory,
  67     /// be compatible with being constructed more than once, though not
  68     /// necessarily in a sane manner. This is safe though.)
  69     pub pre_expansion_passes: Vec<Box<EarlyLintPassFactory>>,
  70     pub early_passes: Vec<Box<EarlyLintPassFactory>>,
  71     pub late_passes: Vec<Box<LateLintPassFactory>>,
  72     /// This is unique in that we construct them per-module, so not once.
  73     pub late_module_passes: Vec<Box<LateLintPassFactory>>,
  74
  75     /// Lints indexed by name.
  76     by_name: FxHashMap<String, TargetLint>,
  77
  78     /// Map of registered lint groups to what lints they expand to.
  79     lint_groups: FxHashMap<&'static str, LintGroup>,
  80 }
  81
  82 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  83 #[derive(Debug)]
  84 enum TargetLint {
  85     /// A direct lint target
  86     Id(LintId),
  87
  88     /// Temporary renaming, used for easing migration pain; see #16545
  89     Renamed(String, LintId),
  90
  91     /// Lint with this name existed previously, but has been removed/deprecated.
  92     /// The string argument is the reason for removal.
  93     Removed(String),
  94
  95     /// A lint name that should give no warnings and have no effect.
  96     ///
  97     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  98     Ignored,
  99 }
 100
 101 pub enum FindLintError {
 102     NotFound,
 103     Removed,
 104 }
 105
 106 struct LintAlias {
 107     name: &'static str,
 108     /// Whether deprecation warnings should be suppressed for this alias.
 109     silent: bool,
 110 }
 111
 112 struct LintGroup {
 113     lint_ids: Vec<LintId>,
 114     from_plugin: bool,
 115     depr: Option<LintAlias>,
 116 }
 117
 118 #[derive(Debug)]
 119 pub enum CheckLintNameResult<'a> {
 120     Ok(&'a [LintId]),
 121     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 122     NoLint(Option<Symbol>),
 123     /// The lint refers to a tool that has not been registered.
 124     NoTool,
 125     /// The lint is either renamed or removed. This is the warning
 126     /// message, and an optional new name (`None` if removed).
 127     Warning(String, Option<String>),
 128     /// The lint is from a tool. If the Option is None, then either
 129     /// the lint does not exist in the tool or the code was not
 130     /// compiled with the tool and therefore the lint was never
 131     /// added to the `LintStore`. Otherwise the `LintId` will be
 132     /// returned as if it where a rustc lint.
 133     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 134 }
 135
 136 impl LintStore {
 137     pub fn new() -> LintStore {
 138         LintStore {
 139             lints: vec![],
 140             pre_expansion_passes: vec![],
 141             early_passes: vec![],
 142             late_passes: vec![],
 143             late_module_passes: vec![],
 144             by_name: Default::default(),
 145             lint_groups: Default::default(),
 146         }
 147     }
 148
 149     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 150         &self.lints
 151     }
 152
 153     pub fn get_lint_groups<'t>(
 154         &'t self,
 155     ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
 156         // This function is not used in a way which observes the order of lints.
 157         #[allow(rustc::potential_query_instability)]
 158         self.lint_groups
 159             .iter()
 160             .filter(|(_, LintGroup { depr, .. })| {
 161                 // Don't display deprecated lint groups.
 162                 depr.is_none()
 163             })
 164             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 165                 (*k, lint_ids.clone(), *from_plugin)
 166             })
 167     }
 168
 169     pub fn register_early_pass(
 170         &mut self,
 171         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 172     ) {
 173         self.early_passes.push(Box::new(pass));
 174     }
 175
 176     /// This lint pass is softly deprecated. It misses expanded code and has caused a few
 177     /// errors in the past. Currently, it is only used in Clippy. New implementations
 178     /// should avoid using this interface, as it might be removed in the future.
 179     ///
 180     /// * See [rust#69838](https://github.com/rust-lang/rust/pull/69838)
 181     /// * See [rust-clippy#5518](https://github.com/rust-lang/rust-clippy/pull/5518)
 182     pub fn register_pre_expansion_pass(
 183         &mut self,
 184         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 185     ) {
 186         self.pre_expansion_passes.push(Box::new(pass));
 187     }
 188
 189     pub fn register_late_pass(
 190         &mut self,
 191         pass: impl for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx>
 192         + 'static
 193         + sync::Send
 194         + sync::Sync,
 195     ) {
 196         self.late_passes.push(Box::new(pass));
 197     }
 198
 199     pub fn register_late_mod_pass(
 200         &mut self,
 201         pass: impl for<'tcx> Fn(TyCtxt<'tcx>) -> LateLintPassObject<'tcx>
 202         + 'static
 203         + sync::Send
 204         + sync::Sync,
 205     ) {
 206         self.late_module_passes.push(Box::new(pass));
 207     }
 208
 209     // Helper method for register_early/late_pass
 210     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 211         for lint in lints {
 212             self.lints.push(lint);
 213
 214             let id = LintId::of(lint);
 215             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 216                 bug!("duplicate specification of lint {}", lint.name_lower())
 217             }
 218
 219             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 220                 if let Some(edition) = reason.edition() {
 221                     self.lint_groups
 222                         .entry(edition.lint_name())
 223                         .or_insert(LintGroup {
 224                             lint_ids: vec![],
 225                             from_plugin: lint.is_plugin,
 226                             depr: None,
 227                         })
 228                         .lint_ids
 229                         .push(id);
 230                 } else {
 231                     // Lints belonging to the `future_incompatible` lint group are lints where a
 232                     // future version of rustc will cause existing code to stop compiling.
 233                     // Lints tied to an edition don't count because they are opt-in.
 234                     self.lint_groups
 235                         .entry("future_incompatible")
 236                         .or_insert(LintGroup {
 237                             lint_ids: vec![],
 238                             from_plugin: lint.is_plugin,
 239                             depr: None,
 240                         })
 241                         .lint_ids
 242                         .push(id);
 243                 }
 244             }
 245         }
 246     }
 247
 248     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 249         self.lint_groups.insert(
 250             alias,
 251             LintGroup {
 252                 lint_ids: vec![],
 253                 from_plugin: false,
 254                 depr: Some(LintAlias { name: lint_name, silent: true }),
 255             },
 256         );
 257     }
 258
 259     pub fn register_group(
 260         &mut self,
 261         from_plugin: bool,
 262         name: &'static str,
 263         deprecated_name: Option<&'static str>,
 264         to: Vec<LintId>,
 265     ) {
 266         let new = self
 267             .lint_groups
 268             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 269             .is_none();
 270         if let Some(deprecated) = deprecated_name {
 271             self.lint_groups.insert(
 272                 deprecated,
 273                 LintGroup {
 274                     lint_ids: vec![],
 275                     from_plugin,
 276                     depr: Some(LintAlias { name, silent: false }),
 277                 },
 278             );
 279         }
 280
 281         if !new {
 282             bug!("duplicate specification of lint group {}", name);
 283         }
 284     }
 285
 286     /// This lint should give no warning and have no effect.
 287     ///
 288     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 289     #[track_caller]
 290     pub fn register_ignored(&mut self, name: &str) {
 291         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 292             bug!("duplicate specification of lint {}", name);
 293         }
 294     }
 295
 296     /// This lint has been renamed; warn about using the new name and apply the lint.
 297     #[track_caller]
 298     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 299         let Some(&Id(target)) = self.by_name.get(new_name) else {
 300             bug!("invalid lint renaming of {} to {}", old_name, new_name);
 301         };
 302         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 303     }
 304
 305     pub fn register_removed(&mut self, name: &str, reason: &str) {
 306         self.by_name.insert(name.into(), Removed(reason.into()));
 307     }
 308
 309     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 310         match self.by_name.get(lint_name) {
 311             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 312             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 313             Some(&Removed(_)) => Err(FindLintError::Removed),
 314             Some(&Ignored) => Ok(vec![]),
 315             None => loop {
 316                 return match self.lint_groups.get(lint_name) {
 317                     Some(LintGroup { lint_ids, depr, .. }) => {
 318                         if let Some(LintAlias { name, .. }) = depr {
 319                             lint_name = name;
 320                             continue;
 321                         }
 322                         Ok(lint_ids.clone())
 323                     }
 324                     None => Err(FindLintError::Removed),
 325                 };
 326             },
 327         }
 328     }
 329
 330     /// Checks the validity of lint names derived from the command line.
 331     pub fn check_lint_name_cmdline(
 332         &self,
 333         sess: &Session,
 334         lint_name: &str,
 335         level: Level,
 336         registered_tools: &RegisteredTools,
 337     ) {
 338         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 339         if lint_name_only == crate::WARNINGS.name_lower() && matches!(level, Level::ForceWarn(_)) {
 340             sess.emit_err(UnsupportedGroup { lint_group: crate::WARNINGS.name_lower() });
 341             return;
 342         }
 343         let lint_name = lint_name.to_string();
 344         match self.check_lint_name(lint_name_only, tool_name, registered_tools) {
 345             CheckLintNameResult::Warning(msg, _) => {
 346                 sess.emit_warning(CheckNameWarning {
 347                     msg,
 348                     sub: RequestedLevel { level, lint_name },
 349                 });
 350             }
 351             CheckLintNameResult::NoLint(suggestion) => {
 352                 sess.emit_err(CheckNameUnknown {
 353                     lint_name: lint_name.clone(),
 354                     suggestion,
 355                     sub: RequestedLevel { level, lint_name },
 356                 });
 357             }
 358             CheckLintNameResult::Tool(result) => {
 359                 if let Err((Some(_), new_name)) = result {
 360                     sess.emit_warning(CheckNameDeprecated {
 361                         lint_name: lint_name.clone(),
 362                         new_name,
 363                         sub: RequestedLevel { level, lint_name },
 364                     });
 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(ref 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(ref 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(ref 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(ref 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         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 487         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 488         let names: Vec<Symbol> = groups.chain(lints).collect();
 489         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 490         CheckLintNameResult::NoLint(suggestion)
 491     }
 492
 493     fn check_tool_name_for_backwards_compat(
 494         &self,
 495         lint_name: &str,
 496         tool_name: &str,
 497     ) -> CheckLintNameResult<'_> {
 498         let complete_name = format!("{}::{}", tool_name, lint_name);
 499         match self.by_name.get(&complete_name) {
 500             None => match self.lint_groups.get(&*complete_name) {
 501                 // Now we are sure, that this lint exists nowhere
 502                 None => self.no_lint_suggestion(lint_name),
 503                 Some(LintGroup { lint_ids, depr, .. }) => {
 504                     // Reaching this would be weird, but let's cover this case anyway
 505                     if let Some(LintAlias { name, silent }) = depr {
 506                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 507                         return if *silent {
 508                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 509                         } else {
 510                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 511                         };
 512                     }
 513                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 514                 }
 515             },
 516             Some(&Id(ref id)) => {
 517                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 518             }
 519             Some(other) => {
 520                 debug!("got renamed lint {:?}", other);
 521                 CheckLintNameResult::NoLint(None)
 522             }
 523         }
 524     }
 525 }
 526
 527 /// Context for lint checking outside of type inference.
 528 pub struct LateContext<'tcx> {
 529     /// Type context we're checking in.
 530     pub tcx: TyCtxt<'tcx>,
 531
 532     /// Current body, or `None` if outside a body.
 533     pub enclosing_body: Option<hir::BodyId>,
 534
 535     /// Type-checking results for the current body. Access using the `typeck_results`
 536     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 537     // FIXME(eddyb) move all the code accessing internal fields like this,
 538     // to this module, to avoid exposing it to lint logic.
 539     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 540
 541     /// Parameter environment for the item we are in.
 542     pub param_env: ty::ParamEnv<'tcx>,
 543
 544     /// Items accessible from the crate being checked.
 545     pub effective_visibilities: &'tcx EffectiveVisibilities,
 546
 547     /// The store of registered lints and the lint levels.
 548     pub lint_store: &'tcx LintStore,
 549
 550     pub last_node_with_lint_attrs: hir::HirId,
 551
 552     /// Generic type parameters in scope for the item we are in.
 553     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 554
 555     /// We are only looking at one module
 556     pub only_module: bool,
 557 }
 558
 559 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 560 pub struct EarlyContext<'a> {
 561     pub builder: LintLevelsBuilder<'a, crate::levels::TopDown>,
 562     pub buffered: LintBuffer,
 563 }
 564
 565 pub trait LintPassObject: Sized {}
 566
 567 impl LintPassObject for EarlyLintPassObject {}
 568
 569 impl LintPassObject for LateLintPassObject<'_> {}
 570
 571 pub trait LintContext: Sized {
 572     type PassObject: LintPassObject;
 573
 574     fn sess(&self) -> &Session;
 575     fn lints(&self) -> &LintStore;
 576
 577     /// Emit a lint at the appropriate level, with an optional associated span and an existing diagnostic.
 578     ///
 579     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 580     ///
 581     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 582     #[rustc_lint_diagnostics]
 583     fn lookup_with_diagnostics(
 584         &self,
 585         lint: &'static Lint,
 586         span: Option<impl Into<MultiSpan>>,
 587         msg: impl Into<DiagnosticMessage>,
 588         decorate: impl for<'a, 'b> FnOnce(
 589             &'b mut DiagnosticBuilder<'a, ()>,
 590         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 591         diagnostic: BuiltinLintDiagnostics,
 592     ) {
 593         // We first generate a blank diagnostic.
 594         self.lookup(lint, span, msg,|db| {
 595             // Now, set up surrounding context.
 596             let sess = self.sess();
 597             match diagnostic {
 598                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
 599                     let spans: Vec<_> = content
 600                         .char_indices()
 601                         .filter_map(|(i, c)| {
 602                             TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
 603                                 let lo = span.lo() + BytePos(2 + i as u32);
 604                                 (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
 605                             })
 606                         })
 607                         .collect();
 608                     let (an, s) = match spans.len() {
 609                         1 => ("an ", ""),
 610                         _ => ("", "s"),
 611                     };
 612                     db.span_label(span, &format!(
 613                         "this comment contains {}invisible unicode text flow control codepoint{}",
 614                         an,
 615                         s,
 616                     ));
 617                     for (c, span) in &spans {
 618                         db.span_label(*span, format!("{:?}", c));
 619                     }
 620                     db.note(
 621                         "these kind of unicode codepoints change the way text flows on \
 622                          applications that support them, but can cause confusion because they \
 623                          change the order of characters on the screen",
 624                     );
 625                     if !spans.is_empty() {
 626                         db.multipart_suggestion_with_style(
 627                             "if their presence wasn't intentional, you can remove them",
 628                             spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
 629                             Applicability::MachineApplicable,
 630                             SuggestionStyle::HideCodeAlways,
 631                         );
 632                     }
 633                 },
 634                 BuiltinLintDiagnostics::Normal => (),
 635                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 636                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 637                         Ok(ref s) => {
 638                             // FIXME(Manishearth) ideally the emitting code
 639                             // can tell us whether or not this is global
 640                             let opt_colon =
 641                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 642
 643                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 644                         }
 645                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 646                     };
 647                     db.span_suggestion(span, "use `crate`", sugg, app);
 648                 }
 649                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 650                     db.span_label(
 651                         span,
 652                         "names from parent modules are not accessible without an explicit import",
 653                     );
 654                 }
 655                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 656                     span_def,
 657                 ) => {
 658                     db.span_note(span_def, "the macro is defined here");
 659                 }
 660                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 661                     n,
 662                     path_span,
 663                     incl_angl_brckt,
 664                     insertion_span,
 665                 ) => {
 666                     add_elided_lifetime_in_path_suggestion(
 667                         sess.source_map(),
 668                         db,
 669                         n,
 670                         path_span,
 671                         incl_angl_brckt,
 672                         insertion_span,
 673                     );
 674                 }
 675                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 676                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 677                 }
 678                 BuiltinLintDiagnostics::UnusedImports(message, replaces, in_test_module) => {
 679                     if !replaces.is_empty() {
 680                         db.tool_only_multipart_suggestion(
 681                             &message,
 682                             replaces,
 683                             Applicability::MachineApplicable,
 684                         );
 685                     }
 686
 687                     if let Some(span) = in_test_module {
 688                         db.span_help(
 689                             self.sess().source_map().guess_head_span(span),
 690                             "consider adding a `#[cfg(test)]` to the containing module",
 691                         );
 692                     }
 693                 }
 694                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 695                     for (span, is_imported) in spans {
 696                         let introduced = if is_imported { "imported" } else { "defined" };
 697                         db.span_label(
 698                             span,
 699                             format!("the item `{}` is already {} here", ident, introduced),
 700                         );
 701                     }
 702                 }
 703                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 704                     stability::deprecation_suggestion(db, "macro", suggestion, span)
 705                 }
 706                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 707                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 708                     db.help("to document an item produced by a macro, \
 709                                   the macro must produce the documentation as part of its expansion");
 710                 }
 711                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 712                     db.span_suggestion(span, "remove `mut` from the parameter", ident, Applicability::MachineApplicable);
 713                 }
 714                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 715                     db.span_label(span, "ABI should be specified here");
 716                     db.help(&format!("the default ABI is {}", default_abi.name()));
 717                 }
 718                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 719                     db.span_label(span, "the attribute is introduced here");
 720                 }
 721                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 722                     db.note(&note);
 723                 }
 724                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 725                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 726                 }
 727                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 728                     db.span_label(span, "unknown prefix");
 729                     db.span_suggestion_verbose(
 730                         span.shrink_to_hi(),
 731                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 732                         " ",
 733                         Applicability::MachineApplicable,
 734                     );
 735                 }
 736                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 737                     attr_name,
 738                     macro_name,
 739                     invoc_span
 740                 } => {
 741                     db.span_note(
 742                         invoc_span,
 743                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 744                     );
 745                 }
 746                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 747                     if is_trailing {
 748                         db.note("macro invocations at the end of a block are treated as expressions");
 749                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 750                     }
 751                 }
 752                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 753                     db.multipart_suggestion(
 754                         "wrap this expression in parentheses",
 755                         vec![(span.shrink_to_lo(), "(".to_string()),
 756                              (span.shrink_to_hi(), ")".to_string())],
 757                         Applicability::MachineApplicable
 758                     );
 759                 }
 760                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 761                     db.help(&help);
 762                     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");
 763                 },
 764                 BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), None) => {
 765                     let Some(names_valid) = &sess.parse_sess.check_config.names_valid else {
 766                         bug!("it shouldn't be possible to have a diagnostic on a name if name checking is not enabled");
 767                     };
 768                     let possibilities: Vec<Symbol> = names_valid.iter().map(|s| *s).collect();
 769
 770                     // Suggest the most probable if we found one
 771                     if let Some(best_match) = find_best_match_for_name(&possibilities, name, None) {
 772                         db.span_suggestion(name_span, "did you mean", best_match, Applicability::MaybeIncorrect);
 773                     }
 774                 },
 775                 BuiltinLintDiagnostics::UnexpectedCfg((name, name_span), Some((value, value_span))) => {
 776                     let Some(values) = &sess.parse_sess.check_config.values_valid.get(&name) else {
 777                         bug!("it shouldn't be possible to have a diagnostic on a value whose name is not in values");
 778                     };
 779                     let possibilities: Vec<Symbol> = values.iter().map(|&s| s).collect();
 780
 781                     // Show the full list if all possible values for a given name, but don't do it
 782                     // for names as the possibilities could be very long
 783                     if !possibilities.is_empty() {
 784                         {
 785                             let mut possibilities = possibilities.iter().map(Symbol::as_str).collect::<Vec<_>>();
 786                             possibilities.sort();
 787
 788                             let possibilities = possibilities.join(", ");
 789                             db.note(&format!("expected values for `{name}` are: {possibilities}"));
 790                         }
 791
 792                         // Suggest the most probable if we found one
 793                         if let Some(best_match) = find_best_match_for_name(&possibilities, value, None) {
 794                             db.span_suggestion(value_span, "did you mean", format!("\"{best_match}\""), Applicability::MaybeIncorrect);
 795                         }
 796                     } else {
 797                         db.note(&format!("no expected value for `{name}`"));
 798                         if name != sym::feature {
 799                             db.span_suggestion(name_span.shrink_to_hi().to(value_span), "remove the value", "", Applicability::MaybeIncorrect);
 800                         }
 801                     }
 802                 },
 803                 BuiltinLintDiagnostics::DeprecatedWhereclauseLocation(new_span, suggestion) => {
 804                     db.multipart_suggestion(
 805                         "move it to the end of the type declaration",
 806                         vec![(db.span.primary_span().unwrap(), "".to_string()), (new_span, suggestion)],
 807                         Applicability::MachineApplicable,
 808                     );
 809                     db.note(
 810                         "see issue #89122 <https://github.com/rust-lang/rust/issues/89122> for more information",
 811                     );
 812                 },
 813                 BuiltinLintDiagnostics::SingleUseLifetime {
 814                     param_span,
 815                     use_span: Some((use_span, elide)),
 816                     deletion_span,
 817                 } => {
 818                     debug!(?param_span, ?use_span, ?deletion_span);
 819                     db.span_label(param_span, "this lifetime...");
 820                     db.span_label(use_span, "...is used only here");
 821                     let msg = "elide the single-use lifetime";
 822                     let (use_span, replace_lt) = if elide {
 823                         let use_span = sess.source_map().span_extend_while(
 824                             use_span,
 825                             char::is_whitespace,
 826                         ).unwrap_or(use_span);
 827                         (use_span, String::new())
 828                     } else {
 829                         (use_span, "'_".to_owned())
 830                     };
 831                     db.multipart_suggestion(
 832                         msg,
 833                         vec![(deletion_span, String::new()), (use_span, replace_lt)],
 834                         Applicability::MachineApplicable,
 835                     );
 836                 },
 837                 BuiltinLintDiagnostics::SingleUseLifetime {
 838                     param_span: _,
 839                     use_span: None,
 840                     deletion_span,
 841                 } => {
 842                     debug!(?deletion_span);
 843                     db.span_suggestion(
 844                         deletion_span,
 845                         "elide the unused lifetime",
 846                         "",
 847                         Applicability::MachineApplicable,
 848                     );
 849                 },
 850                 BuiltinLintDiagnostics::NamedArgumentUsedPositionally{ position_sp_to_replace, position_sp_for_msg, named_arg_sp, named_arg_name, is_formatting_arg} => {
 851                     db.span_label(named_arg_sp, "this named argument is referred to by position in formatting string");
 852                     if let Some(positional_arg_for_msg) = position_sp_for_msg {
 853                         let msg = format!("this formatting argument uses named argument `{}` by position", named_arg_name);
 854                         db.span_label(positional_arg_for_msg, msg);
 855                     }
 856
 857                     if let Some(positional_arg_to_replace) = position_sp_to_replace {
 858                         let name = if is_formatting_arg { named_arg_name + "$" } else { named_arg_name };
 859                         let span_to_replace = if let Ok(positional_arg_content) =
 860                             self.sess().source_map().span_to_snippet(positional_arg_to_replace) && positional_arg_content.starts_with(':') {
 861                             positional_arg_to_replace.shrink_to_lo()
 862                         } else {
 863                             positional_arg_to_replace
 864                         };
 865                         db.span_suggestion_verbose(
 866                             span_to_replace,
 867                             "use the named argument by name to avoid ambiguity",
 868                             name,
 869                             Applicability::MaybeIncorrect,
 870                         );
 871                     }
 872                 }
 873             }
 874             // Rewrap `db`, and pass control to the user.
 875             decorate(db)
 876         });
 877     }
 878
 879     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 880     // set the span in their `decorate` function (preferably using set_span).
 881     /// Emit a lint at the appropriate level, with an optional associated span.
 882     ///
 883     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 884     ///
 885     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 886     #[rustc_lint_diagnostics]
 887     fn lookup<S: Into<MultiSpan>>(
 888         &self,
 889         lint: &'static Lint,
 890         span: Option<S>,
 891         msg: impl Into<DiagnosticMessage>,
 892         decorate: impl for<'a, 'b> FnOnce(
 893             &'b mut DiagnosticBuilder<'a, ()>,
 894         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 895     );
 896
 897     /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
 898     /// typically generated by `#[derive(LintDiagnostic)]`).
 899     fn emit_spanned_lint<S: Into<MultiSpan>>(
 900         &self,
 901         lint: &'static Lint,
 902         span: S,
 903         decorator: impl for<'a> DecorateLint<'a, ()>,
 904     ) {
 905         self.lookup(lint, Some(span), decorator.msg(), |diag| decorator.decorate_lint(diag));
 906     }
 907
 908     /// Emit a lint at the appropriate level, with an associated span.
 909     ///
 910     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 911     ///
 912     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 913     #[rustc_lint_diagnostics]
 914     fn struct_span_lint<S: Into<MultiSpan>>(
 915         &self,
 916         lint: &'static Lint,
 917         span: S,
 918         msg: impl Into<DiagnosticMessage>,
 919         decorate: impl for<'a, 'b> FnOnce(
 920             &'b mut DiagnosticBuilder<'a, ()>,
 921         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 922     ) {
 923         self.lookup(lint, Some(span), msg, decorate);
 924     }
 925
 926     /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
 927     /// generated by `#[derive(LintDiagnostic)]`).
 928     fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
 929         self.lookup(lint, None as Option<Span>, decorator.msg(), |diag| {
 930             decorator.decorate_lint(diag)
 931         });
 932     }
 933
 934     /// Emit a lint at the appropriate level, with no associated span.
 935     ///
 936     /// Return value of the `decorate` closure is ignored, see [`struct_lint_level`] for a detailed explanation.
 937     ///
 938     /// [`struct_lint_level`]: rustc_middle::lint::struct_lint_level#decorate-signature
 939     #[rustc_lint_diagnostics]
 940     fn lint(
 941         &self,
 942         lint: &'static Lint,
 943         msg: impl Into<DiagnosticMessage>,
 944         decorate: impl for<'a, 'b> FnOnce(
 945             &'b mut DiagnosticBuilder<'a, ()>,
 946         ) -> &'b mut DiagnosticBuilder<'a, ()>,
 947     ) {
 948         self.lookup(lint, None as Option<Span>, msg, decorate);
 949     }
 950
 951     /// This returns the lint level for the given lint at the current location.
 952     fn get_lint_level(&self, lint: &'static Lint) -> Level;
 953
 954     /// This function can be used to manually fulfill an expectation. This can
 955     /// be used for lints which contain several spans, and should be suppressed,
 956     /// if either location was marked with an expectation.
 957     ///
 958     /// Note that this function should only be called for [`LintExpectationId`]s
 959     /// retrieved from the current lint pass. Buffered or manually created ids can
 960     /// cause ICEs.
 961     fn fulfill_expectation(&self, expectation: LintExpectationId) {
 962         // We need to make sure that submitted expectation ids are correctly fulfilled suppressed
 963         // and stored between compilation sessions. To not manually do these steps, we simply create
 964         // a dummy diagnostic and emit is as usual, which will be suppressed and stored like a normal
 965         // expected lint diagnostic.
 966         self.sess()
 967             .struct_expect(
 968                 "this is a dummy diagnostic, to submit and store an expectation",
 969                 expectation,
 970             )
 971             .emit();
 972     }
 973 }
 974
 975 impl<'a> EarlyContext<'a> {
 976     pub(crate) fn new(
 977         sess: &'a Session,
 978         warn_about_weird_lints: bool,
 979         lint_store: &'a LintStore,
 980         registered_tools: &'a RegisteredTools,
 981         buffered: LintBuffer,
 982     ) -> EarlyContext<'a> {
 983         EarlyContext {
 984             builder: LintLevelsBuilder::new(
 985                 sess,
 986                 warn_about_weird_lints,
 987                 lint_store,
 988                 registered_tools,
 989             ),
 990             buffered,
 991         }
 992     }
 993 }
 994
 995 impl<'tcx> LintContext for LateContext<'tcx> {
 996     type PassObject = LateLintPassObject<'tcx>;
 997
 998     /// Gets the overall compiler `Session` object.
 999     fn sess(&self) -> &Session {
1000         &self.tcx.sess
1001     }
1002
1003     fn lints(&self) -> &LintStore {
1004         &*self.lint_store
1005     }
1006
1007     fn lookup<S: Into<MultiSpan>>(
1008         &self,
1009         lint: &'static Lint,
1010         span: Option<S>,
1011         msg: impl Into<DiagnosticMessage>,
1012         decorate: impl for<'a, 'b> FnOnce(
1013             &'b mut DiagnosticBuilder<'a, ()>,
1014         ) -> &'b mut DiagnosticBuilder<'a, ()>,
1015     ) {
1016         let hir_id = self.last_node_with_lint_attrs;
1017
1018         match span {
1019             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, msg, decorate),
1020             None => self.tcx.struct_lint_node(lint, hir_id, msg, decorate),
1021         }
1022     }
1023
1024     fn get_lint_level(&self, lint: &'static Lint) -> Level {
1025         self.tcx.lint_level_at_node(lint, self.last_node_with_lint_attrs).0
1026     }
1027 }
1028
1029 impl LintContext for EarlyContext<'_> {
1030     type PassObject = EarlyLintPassObject;
1031
1032     /// Gets the overall compiler `Session` object.
1033     fn sess(&self) -> &Session {
1034         &self.builder.sess()
1035     }
1036
1037     fn lints(&self) -> &LintStore {
1038         self.builder.lint_store()
1039     }
1040
1041     fn lookup<S: Into<MultiSpan>>(
1042         &self,
1043         lint: &'static Lint,
1044         span: Option<S>,
1045         msg: impl Into<DiagnosticMessage>,
1046         decorate: impl for<'a, 'b> FnOnce(
1047             &'b mut DiagnosticBuilder<'a, ()>,
1048         ) -> &'b mut DiagnosticBuilder<'a, ()>,
1049     ) {
1050         self.builder.struct_lint(lint, span.map(|s| s.into()), msg, decorate)
1051     }
1052
1053     fn get_lint_level(&self, lint: &'static Lint) -> Level {
1054         self.builder.lint_level(lint).0
1055     }
1056 }
1057
1058 impl<'tcx> LateContext<'tcx> {
1059     /// Gets the type-checking results for the current body,
1060     /// or `None` if outside a body.
1061     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
1062         self.cached_typeck_results.get().or_else(|| {
1063             self.enclosing_body.map(|body| {
1064                 let typeck_results = self.tcx.typeck_body(body);
1065                 self.cached_typeck_results.set(Some(typeck_results));
1066                 typeck_results
1067             })
1068         })
1069     }
1070
1071     /// Gets the type-checking results for the current body.
1072     /// As this will ICE if called outside bodies, only call when working with
1073     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
1074     #[track_caller]
1075     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
1076         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
1077     }
1078
1079     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
1080     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
1081     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
1082     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
1083         match *qpath {
1084             hir::QPath::Resolved(_, ref path) => path.res,
1085             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
1086                 .maybe_typeck_results()
1087                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
1088                 .or_else(|| {
1089                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
1090                         Some(self.tcx.typeck(id.owner.def_id))
1091                     } else {
1092                         None
1093                     }
1094                 })
1095                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
1096                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
1097         }
1098     }
1099
1100     /// Check if a `DefId`'s path matches the given absolute type path usage.
1101     ///
1102     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
1103     /// inherent `impl` blocks are matched with the name of the type.
1104     ///
1105     /// Instead of using this method, it is often preferable to instead use
1106     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
1107     /// as paths get invalidated if the target definition moves.
1108     ///
1109     /// # Examples
1110     ///
1111     /// ```rust,ignore (no context or def id available)
1112     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
1113     ///     // The given `def_id` is that of an `Option` type
1114     /// }
1115     /// ```
1116     ///
1117     /// Used by clippy, but should be replaced by diagnostic items eventually.
1118     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
1119         let names = self.get_def_path(def_id);
1120
1121         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
1122     }
1123
1124     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
1125     ///
1126     /// # Examples
1127     ///
1128     /// ```rust,ignore (no context or def id available)
1129     /// let def_path = cx.get_def_path(def_id);
1130     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
1131     ///     // The given `def_id` is that of an `Option` type
1132     /// }
1133     /// ```
1134     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
1135         pub struct AbsolutePathPrinter<'tcx> {
1136             pub tcx: TyCtxt<'tcx>,
1137         }
1138
1139         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
1140             type Error = !;
1141
1142             type Path = Vec<Symbol>;
1143             type Region = ();
1144             type Type = ();
1145             type DynExistential = ();
1146             type Const = ();
1147
1148             fn tcx(&self) -> TyCtxt<'tcx> {
1149                 self.tcx
1150             }
1151
1152             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
1153                 Ok(())
1154             }
1155
1156             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
1157                 Ok(())
1158             }
1159
1160             fn print_dyn_existential(
1161                 self,
1162                 _predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
1163             ) -> Result<Self::DynExistential, Self::Error> {
1164                 Ok(())
1165             }
1166
1167             fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1168                 Ok(())
1169             }
1170
1171             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1172                 Ok(vec![self.tcx.crate_name(cnum)])
1173             }
1174
1175             fn path_qualified(
1176                 self,
1177                 self_ty: Ty<'tcx>,
1178                 trait_ref: Option<ty::TraitRef<'tcx>>,
1179             ) -> Result<Self::Path, Self::Error> {
1180                 if trait_ref.is_none() {
1181                     if let ty::Adt(def, substs) = self_ty.kind() {
1182                         return self.print_def_path(def.did(), substs);
1183                     }
1184                 }
1185
1186                 // This shouldn't ever be needed, but just in case:
1187                 with_no_trimmed_paths!({
1188                     Ok(vec![match trait_ref {
1189                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1190                         None => Symbol::intern(&format!("<{}>", self_ty)),
1191                     }])
1192                 })
1193             }
1194
1195             fn path_append_impl(
1196                 self,
1197                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1198                 _disambiguated_data: &DisambiguatedDefPathData,
1199                 self_ty: Ty<'tcx>,
1200                 trait_ref: Option<ty::TraitRef<'tcx>>,
1201             ) -> Result<Self::Path, Self::Error> {
1202                 let mut path = print_prefix(self)?;
1203
1204                 // This shouldn't ever be needed, but just in case:
1205                 path.push(match trait_ref {
1206                     Some(trait_ref) => {
1207                         with_no_trimmed_paths!(Symbol::intern(&format!(
1208                             "<impl {} for {}>",
1209                             trait_ref.print_only_trait_path(),
1210                             self_ty
1211                         )))
1212                     }
1213                     None => {
1214                         with_no_trimmed_paths!(Symbol::intern(&format!("<impl {}>", self_ty)))
1215                     }
1216                 });
1217
1218                 Ok(path)
1219             }
1220
1221             fn path_append(
1222                 self,
1223                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1224                 disambiguated_data: &DisambiguatedDefPathData,
1225             ) -> Result<Self::Path, Self::Error> {
1226                 let mut path = print_prefix(self)?;
1227
1228                 // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1229                 if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1230                     return Ok(path);
1231                 }
1232
1233                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1234                 Ok(path)
1235             }
1236
1237             fn path_generic_args(
1238                 self,
1239                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1240                 _args: &[GenericArg<'tcx>],
1241             ) -> Result<Self::Path, Self::Error> {
1242                 print_prefix(self)
1243             }
1244         }
1245
1246         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1247     }
1248
1249     /// Returns the associated type `name` for `self_ty` as an implementation of `trait_id`.
1250     /// Do not invoke without first verifying that the type implements the trait.
1251     pub fn get_associated_type(
1252         &self,
1253         self_ty: Ty<'tcx>,
1254         trait_id: DefId,
1255         name: &str,
1256     ) -> Option<Ty<'tcx>> {
1257         let tcx = self.tcx;
1258         tcx.associated_items(trait_id)
1259             .find_by_name_and_kind(tcx, Ident::from_str(name), ty::AssocKind::Type, trait_id)
1260             .and_then(|assoc| {
1261                 let proj = tcx.mk_projection(assoc.def_id, tcx.mk_substs_trait(self_ty, []));
1262                 tcx.try_normalize_erasing_regions(self.param_env, proj).ok()
1263             })
1264     }
1265 }
1266
1267 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1268     #[inline]
1269     fn data_layout(&self) -> &abi::TargetDataLayout {
1270         &self.tcx.data_layout
1271     }
1272 }
1273
1274 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1275     #[inline]
1276     fn tcx(&self) -> TyCtxt<'tcx> {
1277         self.tcx
1278     }
1279 }
1280
1281 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1282     #[inline]
1283     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1284         self.param_env
1285     }
1286 }
1287
1288 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1289     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1290
1291     #[inline]
1292     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1293         err
1294     }
1295 }
1296
1297 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1298     match lint_name.split_once("::") {
1299         Some((tool_name, lint_name)) => {
1300             let tool_name = Symbol::intern(tool_name);
1301
1302             (Some(tool_name), lint_name)
1303         }
1304         None => (None, lint_name),
1305     }
1306 }