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::levels::LintLevelsBuilder;
  20 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
  21 use rustc_ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
  22 use rustc_data_structures::fx::FxHashMap;
  23 use rustc_data_structures::sync;
  24 use rustc_errors::{add_elided_lifetime_in_path_suggestion, struct_span_err};
  25 use rustc_errors::{
  26     Applicability, DecorateLint, LintDiagnosticBuilder, MultiSpan, SuggestionStyle,
  27 };
  28 use rustc_hir as hir;
  29 use rustc_hir::def::Res;
  30 use rustc_hir::def_id::{CrateNum, DefId};
  31 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  32 use rustc_middle::middle::privacy::AccessLevels;
  33 use rustc_middle::middle::stability;
  34 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  35 use rustc_middle::ty::print::with_no_trimmed_paths;
  36 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
  37 use rustc_session::lint::{BuiltinLintDiagnostics, LintExpectationId};
  38 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  39 use rustc_session::Session;
  40 use rustc_span::lev_distance::find_best_match_for_name;
  41 use rustc_span::symbol::{sym, Ident, Symbol};
  42 use rustc_span::{BytePos, Span, DUMMY_SP};
  43 use rustc_target::abi;
  44 use tracing::debug;
  45
  46 use std::cell::Cell;
  47 use std::iter;
  48 use std::slice;
  49
  50 /// Information about the registered lints.
  51 ///
  52 /// This is basically the subset of `Context` that we can
  53 /// build early in the compile pipeline.
  54 pub struct LintStore {
  55     /// Registered lints.
  56     lints: Vec<&'static Lint>,
  57
  58     /// Constructor functions for each variety of lint pass.
  59     ///
  60     /// These should only be called once, but since we want to avoid locks or
  61     /// interior mutability, we don't enforce this (and lints should, in theory,
  62     /// be compatible with being constructed more than once, though not
  63     /// necessarily in a sane manner. This is safe though.)
  64     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  65     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  66     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  67     /// This is unique in that we construct them per-module, so not once.
  68     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  69
  70     /// Lints indexed by name.
  71     by_name: FxHashMap<String, TargetLint>,
  72
  73     /// Map of registered lint groups to what lints they expand to.
  74     lint_groups: FxHashMap<&'static str, LintGroup>,
  75 }
  76
  77 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  78 #[derive(Debug)]
  79 enum TargetLint {
  80     /// A direct lint target
  81     Id(LintId),
  82
  83     /// Temporary renaming, used for easing migration pain; see #16545
  84     Renamed(String, LintId),
  85
  86     /// Lint with this name existed previously, but has been removed/deprecated.
  87     /// The string argument is the reason for removal.
  88     Removed(String),
  89
  90     /// A lint name that should give no warnings and have no effect.
  91     ///
  92     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  93     Ignored,
  94 }
  95
  96 pub enum FindLintError {
  97     NotFound,
  98     Removed,
  99 }
 100
 101 struct LintAlias {
 102     name: &'static str,
 103     /// Whether deprecation warnings should be suppressed for this alias.
 104     silent: bool,
 105 }
 106
 107 struct LintGroup {
 108     lint_ids: Vec<LintId>,
 109     from_plugin: bool,
 110     depr: Option<LintAlias>,
 111 }
 112
 113 #[derive(Debug)]
 114 pub enum CheckLintNameResult<'a> {
 115     Ok(&'a [LintId]),
 116     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 117     NoLint(Option<Symbol>),
 118     /// The lint refers to a tool that has not been registered.
 119     NoTool,
 120     /// The lint is either renamed or removed. This is the warning
 121     /// message, and an optional new name (`None` if removed).
 122     Warning(String, Option<String>),
 123     /// The lint is from a tool. If the Option is None, then either
 124     /// the lint does not exist in the tool or the code was not
 125     /// compiled with the tool and therefore the lint was never
 126     /// added to the `LintStore`. Otherwise the `LintId` will be
 127     /// returned as if it where a rustc lint.
 128     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 129 }
 130
 131 impl LintStore {
 132     pub fn new() -> LintStore {
 133         LintStore {
 134             lints: vec![],
 135             pre_expansion_passes: vec![],
 136             early_passes: vec![],
 137             late_passes: vec![],
 138             late_module_passes: vec![],
 139             by_name: Default::default(),
 140             lint_groups: Default::default(),
 141         }
 142     }
 143
 144     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 145         &self.lints
 146     }
 147
 148     pub fn get_lint_groups<'t>(
 149         &'t self,
 150     ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
 151         // This function is not used in a way which observes the order of lints.
 152         #[allow(rustc::potential_query_instability)]
 153         self.lint_groups
 154             .iter()
 155             .filter(|(_, LintGroup { depr, .. })| {
 156                 // Don't display deprecated lint groups.
 157                 depr.is_none()
 158             })
 159             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 160                 (*k, lint_ids.clone(), *from_plugin)
 161             })
 162     }
 163
 164     pub fn register_early_pass(
 165         &mut self,
 166         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 167     ) {
 168         self.early_passes.push(Box::new(pass));
 169     }
 170
 171     /// This lint pass is softly deprecated. It misses expanded code and has caused a few
 172     /// errors in the past. Currently, it is only used in Clippy. New implementations
 173     /// should avoid using this interface, as it might be removed in the future.
 174     ///
 175     /// * See [rust#69838](https://github.com/rust-lang/rust/pull/69838)
 176     /// * See [rust-clippy#5518](https://github.com/rust-lang/rust-clippy/pull/5518)
 177     pub fn register_pre_expansion_pass(
 178         &mut self,
 179         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 180     ) {
 181         self.pre_expansion_passes.push(Box::new(pass));
 182     }
 183
 184     pub fn register_late_pass(
 185         &mut self,
 186         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 187     ) {
 188         self.late_passes.push(Box::new(pass));
 189     }
 190
 191     pub fn register_late_mod_pass(
 192         &mut self,
 193         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 194     ) {
 195         self.late_module_passes.push(Box::new(pass));
 196     }
 197
 198     // Helper method for register_early/late_pass
 199     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 200         for lint in lints {
 201             self.lints.push(lint);
 202
 203             let id = LintId::of(lint);
 204             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 205                 bug!("duplicate specification of lint {}", lint.name_lower())
 206             }
 207
 208             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 209                 if let Some(edition) = reason.edition() {
 210                     self.lint_groups
 211                         .entry(edition.lint_name())
 212                         .or_insert(LintGroup {
 213                             lint_ids: vec![],
 214                             from_plugin: lint.is_plugin,
 215                             depr: None,
 216                         })
 217                         .lint_ids
 218                         .push(id);
 219                 } else {
 220                     // Lints belonging to the `future_incompatible` lint group are lints where a
 221                     // future version of rustc will cause existing code to stop compiling.
 222                     // Lints tied to an edition don't count because they are opt-in.
 223                     self.lint_groups
 224                         .entry("future_incompatible")
 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                 }
 233             }
 234         }
 235     }
 236
 237     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 238         self.lint_groups.insert(
 239             alias,
 240             LintGroup {
 241                 lint_ids: vec![],
 242                 from_plugin: false,
 243                 depr: Some(LintAlias { name: lint_name, silent: true }),
 244             },
 245         );
 246     }
 247
 248     pub fn register_group(
 249         &mut self,
 250         from_plugin: bool,
 251         name: &'static str,
 252         deprecated_name: Option<&'static str>,
 253         to: Vec<LintId>,
 254     ) {
 255         let new = self
 256             .lint_groups
 257             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 258             .is_none();
 259         if let Some(deprecated) = deprecated_name {
 260             self.lint_groups.insert(
 261                 deprecated,
 262                 LintGroup {
 263                     lint_ids: vec![],
 264                     from_plugin,
 265                     depr: Some(LintAlias { name, silent: false }),
 266                 },
 267             );
 268         }
 269
 270         if !new {
 271             bug!("duplicate specification of lint group {}", name);
 272         }
 273     }
 274
 275     /// This lint should give no warning and have no effect.
 276     ///
 277     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 278     #[track_caller]
 279     pub fn register_ignored(&mut self, name: &str) {
 280         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 281             bug!("duplicate specification of lint {}", name);
 282         }
 283     }
 284
 285     /// This lint has been renamed; warn about using the new name and apply the lint.
 286     #[track_caller]
 287     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 288         let Some(&Id(target)) = self.by_name.get(new_name) else {
 289             bug!("invalid lint renaming of {} to {}", old_name, new_name);
 290         };
 291         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 292     }
 293
 294     pub fn register_removed(&mut self, name: &str, reason: &str) {
 295         self.by_name.insert(name.into(), Removed(reason.into()));
 296     }
 297
 298     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 299         match self.by_name.get(lint_name) {
 300             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 301             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 302             Some(&Removed(_)) => Err(FindLintError::Removed),
 303             Some(&Ignored) => Ok(vec![]),
 304             None => loop {
 305                 return match self.lint_groups.get(lint_name) {
 306                     Some(LintGroup { lint_ids, depr, .. }) => {
 307                         if let Some(LintAlias { name, .. }) = depr {
 308                             lint_name = name;
 309                             continue;
 310                         }
 311                         Ok(lint_ids.clone())
 312                     }
 313                     None => Err(FindLintError::Removed),
 314                 };
 315             },
 316         }
 317     }
 318
 319     /// Checks the validity of lint names derived from the command line.
 320     pub fn check_lint_name_cmdline(
 321         &self,
 322         sess: &Session,
 323         lint_name: &str,
 324         level: Level,
 325         registered_tools: &RegisteredTools,
 326     ) {
 327         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 328         if lint_name_only == crate::WARNINGS.name_lower() && matches!(level, Level::ForceWarn(_)) {
 329             struct_span_err!(
 330                 sess,
 331                 DUMMY_SP,
 332                 E0602,
 333                 "`{}` lint group is not supported with ´--force-warn´",
 334                 crate::WARNINGS.name_lower()
 335             )
 336             .emit();
 337             return;
 338         }
 339         let db = match self.check_lint_name(lint_name_only, tool_name, registered_tools) {
 340             CheckLintNameResult::Ok(_) => None,
 341             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 342             CheckLintNameResult::NoLint(suggestion) => {
 343                 let mut err =
 344                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 345
 346                 if let Some(suggestion) = suggestion {
 347                     err.help(&format!("did you mean: `{}`", suggestion));
 348                 }
 349
 350                 Some(err.forget_guarantee())
 351             }
 352             CheckLintNameResult::Tool(result) => match result {
 353                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 354                     "lint name `{}` is deprecated \
 355                      and does not have an effect anymore. \
 356                      Use: {}",
 357                     lint_name, new_name
 358                 ))),
 359                 _ => None,
 360             },
 361             CheckLintNameResult::NoTool => Some(
 362                 struct_span_err!(
 363                     sess,
 364                     DUMMY_SP,
 365                     E0602,
 366                     "unknown lint tool: `{}`",
 367                     tool_name.unwrap()
 368                 )
 369                 .forget_guarantee(),
 370             ),
 371         };
 372
 373         if let Some(mut db) = db {
 374             let msg = format!(
 375                 "requested on the command line with `{} {}`",
 376                 match level {
 377                     Level::Allow => "-A",
 378                     Level::Warn => "-W",
 379                     Level::ForceWarn(_) => "--force-warn",
 380                     Level::Deny => "-D",
 381                     Level::Forbid => "-F",
 382                     Level::Expect(_) => {
 383                         unreachable!("lints with the level of `expect` should not run this code");
 384                     }
 385                 },
 386                 lint_name
 387             );
 388             db.note(&msg);
 389             db.emit();
 390         }
 391     }
 392
 393     /// True if this symbol represents a lint group name.
 394     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 395         debug!(
 396             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 397             lint_name,
 398             self.lint_groups.keys().collect::<Vec<_>>()
 399         );
 400         let lint_name_str = lint_name.as_str();
 401         self.lint_groups.contains_key(lint_name_str) || {
 402             let warnings_name_str = crate::WARNINGS.name_lower();
 403             lint_name_str == warnings_name_str
 404         }
 405     }
 406
 407     /// Checks the name of a lint for its existence, and whether it was
 408     /// renamed or removed. Generates a DiagnosticBuilder containing a
 409     /// warning for renamed and removed lints. This is over both lint
 410     /// names from attributes and those passed on the command line. Since
 411     /// it emits non-fatal warnings and there are *two* lint passes that
 412     /// inspect attributes, this is only run from the late pass to avoid
 413     /// printing duplicate warnings.
 414     pub fn check_lint_name(
 415         &self,
 416         lint_name: &str,
 417         tool_name: Option<Symbol>,
 418         registered_tools: &RegisteredTools,
 419     ) -> CheckLintNameResult<'_> {
 420         if let Some(tool_name) = tool_name {
 421             // FIXME: rustc and rustdoc are considered tools for lints, but not for attributes.
 422             if tool_name != sym::rustc
 423                 && tool_name != sym::rustdoc
 424                 && !registered_tools.contains(&Ident::with_dummy_span(tool_name))
 425             {
 426                 return CheckLintNameResult::NoTool;
 427             }
 428         }
 429
 430         let complete_name = if let Some(tool_name) = tool_name {
 431             format!("{}::{}", tool_name, lint_name)
 432         } else {
 433             lint_name.to_string()
 434         };
 435         // If the lint was scoped with `tool::` check if the tool lint exists
 436         if let Some(tool_name) = tool_name {
 437             match self.by_name.get(&complete_name) {
 438                 None => match self.lint_groups.get(&*complete_name) {
 439                     // If the lint isn't registered, there are two possibilities:
 440                     None => {
 441                         // 1. The tool is currently running, so this lint really doesn't exist.
 442                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 443                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 444                         let tool_prefix = format!("{}::", tool_name);
 445                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 446                             self.no_lint_suggestion(&complete_name)
 447                         } else {
 448                             // 2. The tool isn't currently running, so no lints will be registered.
 449                             // To avoid giving a false positive, ignore all unknown lints.
 450                             CheckLintNameResult::Tool(Err((None, String::new())))
 451                         };
 452                     }
 453                     Some(LintGroup { lint_ids, .. }) => {
 454                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 455                     }
 456                 },
 457                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 458                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 459                 // to treat tool_lints and rustc lints different and can use the code below.
 460                 _ => {}
 461             }
 462         }
 463         match self.by_name.get(&complete_name) {
 464             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 465                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 466                 Some(new_name.to_owned()),
 467             ),
 468             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 469                 format!("lint `{}` has been removed: {}", complete_name, reason),
 470                 None,
 471             ),
 472             None => match self.lint_groups.get(&*complete_name) {
 473                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 474                 // variant of this lint
 475                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 476                 Some(LintGroup { lint_ids, depr, .. }) => {
 477                     // Check if the lint group name is deprecated
 478                     if let Some(LintAlias { name, silent }) = depr {
 479                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 480                         return if *silent {
 481                             CheckLintNameResult::Ok(&lint_ids)
 482                         } else {
 483                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 484                         };
 485                     }
 486                     CheckLintNameResult::Ok(&lint_ids)
 487                 }
 488             },
 489             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 490             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 491         }
 492     }
 493
 494     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 495         let name_lower = lint_name.to_lowercase();
 496
 497         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 498             // First check if the lint name is (partly) in upper case instead of lower case...
 499             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 500         }
 501         // ...if not, search for lints with a similar name
 502         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 503         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 504         let names: Vec<Symbol> = groups.chain(lints).collect();
 505         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 506         CheckLintNameResult::NoLint(suggestion)
 507     }
 508
 509     fn check_tool_name_for_backwards_compat(
 510         &self,
 511         lint_name: &str,
 512         tool_name: &str,
 513     ) -> CheckLintNameResult<'_> {
 514         let complete_name = format!("{}::{}", tool_name, lint_name);
 515         match self.by_name.get(&complete_name) {
 516             None => match self.lint_groups.get(&*complete_name) {
 517                 // Now we are sure, that this lint exists nowhere
 518                 None => self.no_lint_suggestion(lint_name),
 519                 Some(LintGroup { lint_ids, depr, .. }) => {
 520                     // Reaching this would be weird, but let's cover this case anyway
 521                     if let Some(LintAlias { name, silent }) = depr {
 522                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 523                         return if *silent {
 524                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 525                         } else {
 526                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 527                         };
 528                     }
 529                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 530                 }
 531             },
 532             Some(&Id(ref id)) => {
 533                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 534             }
 535             Some(other) => {
 536                 tracing::debug!("got renamed lint {:?}", other);
 537                 CheckLintNameResult::NoLint(None)
 538             }
 539         }
 540     }
 541 }
 542
 543 /// Context for lint checking outside of type inference.
 544 pub struct LateContext<'tcx> {
 545     /// Type context we're checking in.
 546     pub tcx: TyCtxt<'tcx>,
 547
 548     /// Current body, or `None` if outside a body.
 549     pub enclosing_body: Option<hir::BodyId>,
 550
 551     /// Type-checking results for the current body. Access using the `typeck_results`
 552     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 553     // FIXME(eddyb) move all the code accessing internal fields like this,
 554     // to this module, to avoid exposing it to lint logic.
 555     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 556
 557     /// Parameter environment for the item we are in.
 558     pub param_env: ty::ParamEnv<'tcx>,
 559
 560     /// Items accessible from the crate being checked.
 561     pub access_levels: &'tcx AccessLevels,
 562
 563     /// The store of registered lints and the lint levels.
 564     pub lint_store: &'tcx LintStore,
 565
 566     pub last_node_with_lint_attrs: hir::HirId,
 567
 568     /// Generic type parameters in scope for the item we are in.
 569     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 570
 571     /// We are only looking at one module
 572     pub only_module: bool,
 573 }
 574
 575 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 576 pub struct EarlyContext<'a> {
 577     pub builder: LintLevelsBuilder<'a>,
 578     pub buffered: LintBuffer,
 579 }
 580
 581 pub trait LintPassObject: Sized {}
 582
 583 impl LintPassObject for EarlyLintPassObject {}
 584
 585 impl LintPassObject for LateLintPassObject {}
 586
 587 pub trait LintContext: Sized {
 588     type PassObject: LintPassObject;
 589
 590     fn sess(&self) -> &Session;
 591     fn lints(&self) -> &LintStore;
 592
 593     fn lookup_with_diagnostics(
 594         &self,
 595         lint: &'static Lint,
 596         span: Option<impl Into<MultiSpan>>,
 597         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 598         diagnostic: BuiltinLintDiagnostics,
 599     ) {
 600         self.lookup(lint, span, |lint| {
 601             // We first generate a blank diagnostic.
 602             let mut db = lint.build("");
 603
 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                         &mut 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(&mut 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(positional_arg, named_arg, name) => {
 860                     db.span_label(named_arg, "this named argument is only referred to by position in formatting string");
 861                     if let Some(positional_arg) = positional_arg {
 862                         let msg = format!("this formatting argument uses named argument `{}` by position", name);
 863                         db.span_label(positional_arg, msg);
 864                         db.span_suggestion_verbose(
 865                             positional_arg,
 866                             "use the named argument by name to avoid ambiguity",
 867                             name,
 868                             Applicability::MaybeIncorrect,
 869                         );
 870                     }
 871                 }
 872             }
 873             // Rewrap `db`, and pass control to the user.
 874             decorate(LintDiagnosticBuilder::new(db));
 875         });
 876     }
 877
 878     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 879     // set the span in their `decorate` function (preferably using set_span).
 880     fn lookup<S: Into<MultiSpan>>(
 881         &self,
 882         lint: &'static Lint,
 883         span: Option<S>,
 884         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 885     );
 886
 887     /// Emit a lint at `span` from a lint struct (some type that implements `DecorateLint`,
 888     /// typically generated by `#[derive(LintDiagnostic)]`).
 889     fn emit_spanned_lint<S: Into<MultiSpan>>(
 890         &self,
 891         lint: &'static Lint,
 892         span: S,
 893         decorator: impl for<'a> DecorateLint<'a, ()>,
 894     ) {
 895         self.lookup(lint, Some(span), |diag| decorator.decorate_lint(diag));
 896     }
 897
 898     fn struct_span_lint<S: Into<MultiSpan>>(
 899         &self,
 900         lint: &'static Lint,
 901         span: S,
 902         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 903     ) {
 904         self.lookup(lint, Some(span), decorate);
 905     }
 906
 907     /// Emit a lint from a lint struct (some type that implements `DecorateLint`, typically
 908     /// generated by `#[derive(LintDiagnostic)]`).
 909     fn emit_lint(&self, lint: &'static Lint, decorator: impl for<'a> DecorateLint<'a, ()>) {
 910         self.lookup(lint, None as Option<Span>, |diag| decorator.decorate_lint(diag));
 911     }
 912
 913     /// Emit a lint at the appropriate level, with no associated span.
 914     fn lint(
 915         &self,
 916         lint: &'static Lint,
 917         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 918     ) {
 919         self.lookup(lint, None as Option<Span>, decorate);
 920     }
 921
 922     /// This returns the lint level for the given lint at the current location.
 923     fn get_lint_level(&self, lint: &'static Lint) -> Level;
 924
 925     /// This function can be used to manually fulfill an expectation. This can
 926     /// be used for lints which contain several spans, and should be suppressed,
 927     /// if either location was marked with an expectation.
 928     ///
 929     /// Note that this function should only be called for [`LintExpectationId`]s
 930     /// retrieved from the current lint pass. Buffered or manually created ids can
 931     /// cause ICEs.
 932     fn fulfill_expectation(&self, expectation: LintExpectationId) {
 933         // We need to make sure that submitted expectation ids are correctly fulfilled suppressed
 934         // and stored between compilation sessions. To not manually do these steps, we simply create
 935         // a dummy diagnostic and emit is as usual, which will be suppressed and stored like a normal
 936         // expected lint diagnostic.
 937         self.sess()
 938             .struct_expect(
 939                 "this is a dummy diagnostic, to submit and store an expectation",
 940                 expectation,
 941             )
 942             .emit();
 943     }
 944 }
 945
 946 impl<'a> EarlyContext<'a> {
 947     pub(crate) fn new(
 948         sess: &'a Session,
 949         warn_about_weird_lints: bool,
 950         lint_store: &'a LintStore,
 951         registered_tools: &'a RegisteredTools,
 952         buffered: LintBuffer,
 953     ) -> EarlyContext<'a> {
 954         EarlyContext {
 955             builder: LintLevelsBuilder::new(
 956                 sess,
 957                 warn_about_weird_lints,
 958                 lint_store,
 959                 registered_tools,
 960             ),
 961             buffered,
 962         }
 963     }
 964 }
 965
 966 impl LintContext for LateContext<'_> {
 967     type PassObject = LateLintPassObject;
 968
 969     /// Gets the overall compiler `Session` object.
 970     fn sess(&self) -> &Session {
 971         &self.tcx.sess
 972     }
 973
 974     fn lints(&self) -> &LintStore {
 975         &*self.lint_store
 976     }
 977
 978     fn lookup<S: Into<MultiSpan>>(
 979         &self,
 980         lint: &'static Lint,
 981         span: Option<S>,
 982         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
 983     ) {
 984         let hir_id = self.last_node_with_lint_attrs;
 985
 986         match span {
 987             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 988             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 989         }
 990     }
 991
 992     fn get_lint_level(&self, lint: &'static Lint) -> Level {
 993         self.tcx.lint_level_at_node(lint, self.last_node_with_lint_attrs).0
 994     }
 995 }
 996
 997 impl LintContext for EarlyContext<'_> {
 998     type PassObject = EarlyLintPassObject;
 999
1000     /// Gets the overall compiler `Session` object.
1001     fn sess(&self) -> &Session {
1002         &self.builder.sess()
1003     }
1004
1005     fn lints(&self) -> &LintStore {
1006         self.builder.lint_store()
1007     }
1008
1009     fn lookup<S: Into<MultiSpan>>(
1010         &self,
1011         lint: &'static Lint,
1012         span: Option<S>,
1013         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a, ()>),
1014     ) {
1015         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
1016     }
1017
1018     fn get_lint_level(&self, lint: &'static Lint) -> Level {
1019         self.builder.lint_level(lint).0
1020     }
1021 }
1022
1023 impl<'tcx> LateContext<'tcx> {
1024     /// Gets the type-checking results for the current body,
1025     /// or `None` if outside a body.
1026     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
1027         self.cached_typeck_results.get().or_else(|| {
1028             self.enclosing_body.map(|body| {
1029                 let typeck_results = self.tcx.typeck_body(body);
1030                 self.cached_typeck_results.set(Some(typeck_results));
1031                 typeck_results
1032             })
1033         })
1034     }
1035
1036     /// Gets the type-checking results for the current body.
1037     /// As this will ICE if called outside bodies, only call when working with
1038     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
1039     #[track_caller]
1040     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
1041         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
1042     }
1043
1044     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
1045     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
1046     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
1047     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
1048         match *qpath {
1049             hir::QPath::Resolved(_, ref path) => path.res,
1050             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
1051                 .maybe_typeck_results()
1052                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
1053                 .or_else(|| {
1054                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
1055                         Some(self.tcx.typeck(id.owner))
1056                     } else {
1057                         None
1058                     }
1059                 })
1060                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
1061                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
1062         }
1063     }
1064
1065     /// Check if a `DefId`'s path matches the given absolute type path usage.
1066     ///
1067     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
1068     /// inherent `impl` blocks are matched with the name of the type.
1069     ///
1070     /// Instead of using this method, it is often preferable to instead use
1071     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
1072     /// as paths get invalidated if the target definition moves.
1073     ///
1074     /// # Examples
1075     ///
1076     /// ```rust,ignore (no context or def id available)
1077     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
1078     ///     // The given `def_id` is that of an `Option` type
1079     /// }
1080     /// ```
1081     ///
1082     /// Used by clippy, but should be replaced by diagnostic items eventually.
1083     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
1084         let names = self.get_def_path(def_id);
1085
1086         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
1087     }
1088
1089     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
1090     ///
1091     /// # Examples
1092     ///
1093     /// ```rust,ignore (no context or def id available)
1094     /// let def_path = cx.get_def_path(def_id);
1095     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
1096     ///     // The given `def_id` is that of an `Option` type
1097     /// }
1098     /// ```
1099     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
1100         pub struct AbsolutePathPrinter<'tcx> {
1101             pub tcx: TyCtxt<'tcx>,
1102         }
1103
1104         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
1105             type Error = !;
1106
1107             type Path = Vec<Symbol>;
1108             type Region = ();
1109             type Type = ();
1110             type DynExistential = ();
1111             type Const = ();
1112
1113             fn tcx(&self) -> TyCtxt<'tcx> {
1114                 self.tcx
1115             }
1116
1117             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
1118                 Ok(())
1119             }
1120
1121             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
1122                 Ok(())
1123             }
1124
1125             fn print_dyn_existential(
1126                 self,
1127                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
1128             ) -> Result<Self::DynExistential, Self::Error> {
1129                 Ok(())
1130             }
1131
1132             fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1133                 Ok(())
1134             }
1135
1136             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1137                 Ok(vec![self.tcx.crate_name(cnum)])
1138             }
1139
1140             fn path_qualified(
1141                 self,
1142                 self_ty: Ty<'tcx>,
1143                 trait_ref: Option<ty::TraitRef<'tcx>>,
1144             ) -> Result<Self::Path, Self::Error> {
1145                 if trait_ref.is_none() {
1146                     if let ty::Adt(def, substs) = self_ty.kind() {
1147                         return self.print_def_path(def.did(), substs);
1148                     }
1149                 }
1150
1151                 // This shouldn't ever be needed, but just in case:
1152                 with_no_trimmed_paths!({
1153                     Ok(vec![match trait_ref {
1154                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1155                         None => Symbol::intern(&format!("<{}>", self_ty)),
1156                     }])
1157                 })
1158             }
1159
1160             fn path_append_impl(
1161                 self,
1162                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1163                 _disambiguated_data: &DisambiguatedDefPathData,
1164                 self_ty: Ty<'tcx>,
1165                 trait_ref: Option<ty::TraitRef<'tcx>>,
1166             ) -> Result<Self::Path, Self::Error> {
1167                 let mut path = print_prefix(self)?;
1168
1169                 // This shouldn't ever be needed, but just in case:
1170                 path.push(match trait_ref {
1171                     Some(trait_ref) => {
1172                         with_no_trimmed_paths!(Symbol::intern(&format!(
1173                             "<impl {} for {}>",
1174                             trait_ref.print_only_trait_path(),
1175                             self_ty
1176                         )))
1177                     }
1178                     None => {
1179                         with_no_trimmed_paths!(Symbol::intern(&format!("<impl {}>", self_ty)))
1180                     }
1181                 });
1182
1183                 Ok(path)
1184             }
1185
1186             fn path_append(
1187                 self,
1188                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1189                 disambiguated_data: &DisambiguatedDefPathData,
1190             ) -> Result<Self::Path, Self::Error> {
1191                 let mut path = print_prefix(self)?;
1192
1193                 // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1194                 if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1195                     return Ok(path);
1196                 }
1197
1198                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1199                 Ok(path)
1200             }
1201
1202             fn path_generic_args(
1203                 self,
1204                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1205                 _args: &[GenericArg<'tcx>],
1206             ) -> Result<Self::Path, Self::Error> {
1207                 print_prefix(self)
1208             }
1209         }
1210
1211         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1212     }
1213 }
1214
1215 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1216     #[inline]
1217     fn data_layout(&self) -> &abi::TargetDataLayout {
1218         &self.tcx.data_layout
1219     }
1220 }
1221
1222 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1223     #[inline]
1224     fn tcx(&self) -> TyCtxt<'tcx> {
1225         self.tcx
1226     }
1227 }
1228
1229 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1230     #[inline]
1231     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1232         self.param_env
1233     }
1234 }
1235
1236 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1237     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1238
1239     #[inline]
1240     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1241         err
1242     }
1243 }
1244
1245 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1246     match lint_name.split_once("::") {
1247         Some((tool_name, lint_name)) => {
1248             let tool_name = Symbol::intern(tool_name);
1249
1250             (Some(tool_name), lint_name)
1251         }
1252         None => (None, lint_name),
1253     }
1254 }