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::{struct_span_err, Applicability, SuggestionStyle};
  25 use rustc_hir as hir;
  26 use rustc_hir::def::Res;
  27 use rustc_hir::def_id::{CrateNum, DefId};
  28 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  29 use rustc_middle::lint::LintDiagnosticBuilder;
  30 use rustc_middle::middle::privacy::AccessLevels;
  31 use rustc_middle::middle::stability;
  32 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  33 use rustc_middle::ty::print::with_no_trimmed_paths;
  34 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
  35 use rustc_serialize::json::Json;
  36 use rustc_session::lint::{BuiltinLintDiagnostics, ExternDepSpec};
  37 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  38 use rustc_session::Session;
  39 use rustc_span::lev_distance::find_best_match_for_name;
  40 use rustc_span::symbol::{sym, Ident, Symbol};
  41 use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
  42 use rustc_target::abi;
  43 use tracing::debug;
  44
  45 use std::cell::Cell;
  46 use std::iter;
  47 use std::slice;
  48
  49 /// Information about the registered lints.
  50 ///
  51 /// This is basically the subset of `Context` that we can
  52 /// build early in the compile pipeline.
  53 pub struct LintStore {
  54     /// Registered lints.
  55     lints: Vec<&'static Lint>,
  56
  57     /// Constructor functions for each variety of lint pass.
  58     ///
  59     /// These should only be called once, but since we want to avoid locks or
  60     /// interior mutability, we don't enforce this (and lints should, in theory,
  61     /// be compatible with being constructed more than once, though not
  62     /// necessarily in a sane manner. This is safe though.)
  63     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  64     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  65     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  66     /// This is unique in that we construct them per-module, so not once.
  67     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  68
  69     /// Lints indexed by name.
  70     by_name: FxHashMap<String, TargetLint>,
  71
  72     /// Map of registered lint groups to what lints they expand to.
  73     lint_groups: FxHashMap<&'static str, LintGroup>,
  74 }
  75
  76 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  77 #[derive(Debug)]
  78 enum TargetLint {
  79     /// A direct lint target
  80     Id(LintId),
  81
  82     /// Temporary renaming, used for easing migration pain; see #16545
  83     Renamed(String, LintId),
  84
  85     /// Lint with this name existed previously, but has been removed/deprecated.
  86     /// The string argument is the reason for removal.
  87     Removed(String),
  88
  89     /// A lint name that should give no warnings and have no effect.
  90     ///
  91     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  92     Ignored,
  93 }
  94
  95 pub enum FindLintError {
  96     NotFound,
  97     Removed,
  98 }
  99
 100 struct LintAlias {
 101     name: &'static str,
 102     /// Whether deprecation warnings should be suppressed for this alias.
 103     silent: bool,
 104 }
 105
 106 struct LintGroup {
 107     lint_ids: Vec<LintId>,
 108     from_plugin: bool,
 109     depr: Option<LintAlias>,
 110 }
 111
 112 pub enum CheckLintNameResult<'a> {
 113     Ok(&'a [LintId]),
 114     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 115     NoLint(Option<Symbol>),
 116     /// The lint refers to a tool that has not been registered.
 117     NoTool,
 118     /// The lint is either renamed or removed. This is the warning
 119     /// message, and an optional new name (`None` if removed).
 120     Warning(String, Option<String>),
 121     /// The lint is from a tool. If the Option is None, then either
 122     /// the lint does not exist in the tool or the code was not
 123     /// compiled with the tool and therefore the lint was never
 124     /// added to the `LintStore`. Otherwise the `LintId` will be
 125     /// returned as if it where a rustc lint.
 126     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 127 }
 128
 129 impl LintStore {
 130     pub fn new() -> LintStore {
 131         LintStore {
 132             lints: vec![],
 133             pre_expansion_passes: vec![],
 134             early_passes: vec![],
 135             late_passes: vec![],
 136             late_module_passes: vec![],
 137             by_name: Default::default(),
 138             lint_groups: Default::default(),
 139         }
 140     }
 141
 142     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 143         &self.lints
 144     }
 145
 146     pub fn get_lint_groups<'t>(
 147         &'t self,
 148     ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
 149         // This function is not used in a way which observes the order of lints.
 150         #[cfg_attr(not(bootstrap), allow(rustc::potential_query_instability))]
 151         self.lint_groups
 152             .iter()
 153             .filter(|(_, LintGroup { depr, .. })| {
 154                 // Don't display deprecated lint groups.
 155                 depr.is_none()
 156             })
 157             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 158                 (*k, lint_ids.clone(), *from_plugin)
 159             })
 160     }
 161
 162     pub fn register_early_pass(
 163         &mut self,
 164         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 165     ) {
 166         self.early_passes.push(Box::new(pass));
 167     }
 168
 169     /// Used by clippy.
 170     pub fn register_pre_expansion_pass(
 171         &mut self,
 172         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 173     ) {
 174         self.pre_expansion_passes.push(Box::new(pass));
 175     }
 176
 177     pub fn register_late_pass(
 178         &mut self,
 179         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 180     ) {
 181         self.late_passes.push(Box::new(pass));
 182     }
 183
 184     pub fn register_late_mod_pass(
 185         &mut self,
 186         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 187     ) {
 188         self.late_module_passes.push(Box::new(pass));
 189     }
 190
 191     // Helper method for register_early/late_pass
 192     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 193         for lint in lints {
 194             self.lints.push(lint);
 195
 196             let id = LintId::of(lint);
 197             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 198                 bug!("duplicate specification of lint {}", lint.name_lower())
 199             }
 200
 201             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 202                 if let Some(edition) = reason.edition() {
 203                     self.lint_groups
 204                         .entry(edition.lint_name())
 205                         .or_insert(LintGroup {
 206                             lint_ids: vec![],
 207                             from_plugin: lint.is_plugin,
 208                             depr: None,
 209                         })
 210                         .lint_ids
 211                         .push(id);
 212                 } else {
 213                     // Lints belonging to the `future_incompatible` lint group are lints where a
 214                     // future version of rustc will cause existing code to stop compiling.
 215                     // Lints tied to an edition don't count because they are opt-in.
 216                     self.lint_groups
 217                         .entry("future_incompatible")
 218                         .or_insert(LintGroup {
 219                             lint_ids: vec![],
 220                             from_plugin: lint.is_plugin,
 221                             depr: None,
 222                         })
 223                         .lint_ids
 224                         .push(id);
 225                 }
 226             }
 227         }
 228     }
 229
 230     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 231         self.lint_groups.insert(
 232             alias,
 233             LintGroup {
 234                 lint_ids: vec![],
 235                 from_plugin: false,
 236                 depr: Some(LintAlias { name: lint_name, silent: true }),
 237             },
 238         );
 239     }
 240
 241     pub fn register_group(
 242         &mut self,
 243         from_plugin: bool,
 244         name: &'static str,
 245         deprecated_name: Option<&'static str>,
 246         to: Vec<LintId>,
 247     ) {
 248         let new = self
 249             .lint_groups
 250             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 251             .is_none();
 252         if let Some(deprecated) = deprecated_name {
 253             self.lint_groups.insert(
 254                 deprecated,
 255                 LintGroup {
 256                     lint_ids: vec![],
 257                     from_plugin,
 258                     depr: Some(LintAlias { name, silent: false }),
 259                 },
 260             );
 261         }
 262
 263         if !new {
 264             bug!("duplicate specification of lint group {}", name);
 265         }
 266     }
 267
 268     /// This lint should give no warning and have no effect.
 269     ///
 270     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 271     #[track_caller]
 272     pub fn register_ignored(&mut self, name: &str) {
 273         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 274             bug!("duplicate specification of lint {}", name);
 275         }
 276     }
 277
 278     /// This lint has been renamed; warn about using the new name and apply the lint.
 279     #[track_caller]
 280     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 281         let target = match self.by_name.get(new_name) {
 282             Some(&Id(lint_id)) => lint_id,
 283             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 284         };
 285         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 286     }
 287
 288     pub fn register_removed(&mut self, name: &str, reason: &str) {
 289         self.by_name.insert(name.into(), Removed(reason.into()));
 290     }
 291
 292     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 293         match self.by_name.get(lint_name) {
 294             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 295             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 296             Some(&Removed(_)) => Err(FindLintError::Removed),
 297             Some(&Ignored) => Ok(vec![]),
 298             None => loop {
 299                 return match self.lint_groups.get(lint_name) {
 300                     Some(LintGroup { lint_ids, depr, .. }) => {
 301                         if let Some(LintAlias { name, .. }) = depr {
 302                             lint_name = name;
 303                             continue;
 304                         }
 305                         Ok(lint_ids.clone())
 306                     }
 307                     None => Err(FindLintError::Removed),
 308                 };
 309             },
 310         }
 311     }
 312
 313     /// Checks the validity of lint names derived from the command line.
 314     pub fn check_lint_name_cmdline(
 315         &self,
 316         sess: &Session,
 317         lint_name: &str,
 318         level: Level,
 319         registered_tools: &RegisteredTools,
 320     ) {
 321         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 322         if lint_name_only == crate::WARNINGS.name_lower() && level == Level::ForceWarn {
 323             return struct_span_err!(
 324                 sess,
 325                 DUMMY_SP,
 326                 E0602,
 327                 "`{}` lint group is not supported with ´--force-warn´",
 328                 crate::WARNINGS.name_lower()
 329             )
 330             .emit();
 331         }
 332         let db = match self.check_lint_name(lint_name_only, tool_name, registered_tools) {
 333             CheckLintNameResult::Ok(_) => None,
 334             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 335             CheckLintNameResult::NoLint(suggestion) => {
 336                 let mut err =
 337                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 338
 339                 if let Some(suggestion) = suggestion {
 340                     err.help(&format!("did you mean: `{}`", suggestion));
 341                 }
 342
 343                 Some(err)
 344             }
 345             CheckLintNameResult::Tool(result) => match result {
 346                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 347                     "lint name `{}` is deprecated \
 348                      and does not have an effect anymore. \
 349                      Use: {}",
 350                     lint_name, new_name
 351                 ))),
 352                 _ => None,
 353             },
 354             CheckLintNameResult::NoTool => Some(struct_span_err!(
 355                 sess,
 356                 DUMMY_SP,
 357                 E0602,
 358                 "unknown lint tool: `{}`",
 359                 tool_name.unwrap()
 360             )),
 361         };
 362
 363         if let Some(mut db) = db {
 364             let msg = format!(
 365                 "requested on the command line with `{} {}`",
 366                 match level {
 367                     Level::Allow => "-A",
 368                     Level::Warn => "-W",
 369                     Level::ForceWarn => "--force-warn",
 370                     Level::Deny => "-D",
 371                     Level::Forbid => "-F",
 372                 },
 373                 lint_name
 374             );
 375             db.note(&msg);
 376             db.emit();
 377         }
 378     }
 379
 380     /// True if this symbol represents a lint group name.
 381     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 382         debug!(
 383             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 384             lint_name,
 385             self.lint_groups.keys().collect::<Vec<_>>()
 386         );
 387         let lint_name_str = lint_name.as_str();
 388         self.lint_groups.contains_key(lint_name_str) || {
 389             let warnings_name_str = crate::WARNINGS.name_lower();
 390             lint_name_str == warnings_name_str
 391         }
 392     }
 393
 394     /// Checks the name of a lint for its existence, and whether it was
 395     /// renamed or removed. Generates a DiagnosticBuilder containing a
 396     /// warning for renamed and removed lints. This is over both lint
 397     /// names from attributes and those passed on the command line. Since
 398     /// it emits non-fatal warnings and there are *two* lint passes that
 399     /// inspect attributes, this is only run from the late pass to avoid
 400     /// printing duplicate warnings.
 401     pub fn check_lint_name(
 402         &self,
 403         lint_name: &str,
 404         tool_name: Option<Symbol>,
 405         registered_tools: &RegisteredTools,
 406     ) -> CheckLintNameResult<'_> {
 407         if let Some(tool_name) = tool_name {
 408             // FIXME: rustc and rustdoc are considered tools for lints, but not for attributes.
 409             if tool_name != sym::rustc
 410                 && tool_name != sym::rustdoc
 411                 && !registered_tools.contains(&Ident::with_dummy_span(tool_name))
 412             {
 413                 return CheckLintNameResult::NoTool;
 414             }
 415         }
 416
 417         let complete_name = if let Some(tool_name) = tool_name {
 418             format!("{}::{}", tool_name, lint_name)
 419         } else {
 420             lint_name.to_string()
 421         };
 422         // If the lint was scoped with `tool::` check if the tool lint exists
 423         if let Some(tool_name) = tool_name {
 424             match self.by_name.get(&complete_name) {
 425                 None => match self.lint_groups.get(&*complete_name) {
 426                     // If the lint isn't registered, there are two possibilities:
 427                     None => {
 428                         // 1. The tool is currently running, so this lint really doesn't exist.
 429                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 430                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 431                         let tool_prefix = format!("{}::", tool_name);
 432                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 433                             self.no_lint_suggestion(&complete_name)
 434                         } else {
 435                             // 2. The tool isn't currently running, so no lints will be registered.
 436                             // To avoid giving a false positive, ignore all unknown lints.
 437                             CheckLintNameResult::Tool(Err((None, String::new())))
 438                         };
 439                     }
 440                     Some(LintGroup { lint_ids, .. }) => {
 441                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 442                     }
 443                 },
 444                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 445                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 446                 // to treat tool_lints and rustc lints different and can use the code below.
 447                 _ => {}
 448             }
 449         }
 450         match self.by_name.get(&complete_name) {
 451             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 452                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 453                 Some(new_name.to_owned()),
 454             ),
 455             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 456                 format!("lint `{}` has been removed: {}", complete_name, reason),
 457                 None,
 458             ),
 459             None => match self.lint_groups.get(&*complete_name) {
 460                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 461                 // variant of this lint
 462                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 463                 Some(LintGroup { lint_ids, depr, .. }) => {
 464                     // Check if the lint group name is deprecated
 465                     if let Some(LintAlias { name, silent }) = depr {
 466                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 467                         return if *silent {
 468                             CheckLintNameResult::Ok(&lint_ids)
 469                         } else {
 470                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 471                         };
 472                     }
 473                     CheckLintNameResult::Ok(&lint_ids)
 474                 }
 475             },
 476             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 477             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 478         }
 479     }
 480
 481     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 482         let name_lower = lint_name.to_lowercase();
 483
 484         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 485             // First check if the lint name is (partly) in upper case instead of lower case...
 486             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 487         }
 488         // ...if not, search for lints with a similar name
 489         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 490         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 491         let names: Vec<Symbol> = groups.chain(lints).collect();
 492         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 493         CheckLintNameResult::NoLint(suggestion)
 494     }
 495
 496     fn check_tool_name_for_backwards_compat(
 497         &self,
 498         lint_name: &str,
 499         tool_name: &str,
 500     ) -> CheckLintNameResult<'_> {
 501         let complete_name = format!("{}::{}", tool_name, lint_name);
 502         match self.by_name.get(&complete_name) {
 503             None => match self.lint_groups.get(&*complete_name) {
 504                 // Now we are sure, that this lint exists nowhere
 505                 None => self.no_lint_suggestion(lint_name),
 506                 Some(LintGroup { lint_ids, depr, .. }) => {
 507                     // Reaching this would be weird, but let's cover this case anyway
 508                     if let Some(LintAlias { name, silent }) = depr {
 509                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 510                         return if *silent {
 511                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 512                         } else {
 513                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 514                         };
 515                     }
 516                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 517                 }
 518             },
 519             Some(&Id(ref id)) => {
 520                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 521             }
 522             Some(other) => {
 523                 tracing::debug!("got renamed lint {:?}", other);
 524                 CheckLintNameResult::NoLint(None)
 525             }
 526         }
 527     }
 528 }
 529
 530 /// Context for lint checking outside of type inference.
 531 pub struct LateContext<'tcx> {
 532     /// Type context we're checking in.
 533     pub tcx: TyCtxt<'tcx>,
 534
 535     /// Current body, or `None` if outside a body.
 536     pub enclosing_body: Option<hir::BodyId>,
 537
 538     /// Type-checking results for the current body. Access using the `typeck_results`
 539     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 540     // FIXME(eddyb) move all the code accessing internal fields like this,
 541     // to this module, to avoid exposing it to lint logic.
 542     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 543
 544     /// Parameter environment for the item we are in.
 545     pub param_env: ty::ParamEnv<'tcx>,
 546
 547     /// Items accessible from the crate being checked.
 548     pub access_levels: &'tcx AccessLevels,
 549
 550     /// The store of registered lints and the lint levels.
 551     pub lint_store: &'tcx LintStore,
 552
 553     pub last_node_with_lint_attrs: hir::HirId,
 554
 555     /// Generic type parameters in scope for the item we are in.
 556     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 557
 558     /// We are only looking at one module
 559     pub only_module: bool,
 560 }
 561
 562 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 563 pub struct EarlyContext<'a> {
 564     pub builder: LintLevelsBuilder<'a>,
 565     pub buffered: LintBuffer,
 566 }
 567
 568 pub trait LintPassObject: Sized {}
 569
 570 impl LintPassObject for EarlyLintPassObject {}
 571
 572 impl LintPassObject for LateLintPassObject {}
 573
 574 pub trait LintContext: Sized {
 575     type PassObject: LintPassObject;
 576
 577     fn sess(&self) -> &Session;
 578     fn lints(&self) -> &LintStore;
 579
 580     fn lookup_with_diagnostics(
 581         &self,
 582         lint: &'static Lint,
 583         span: Option<impl Into<MultiSpan>>,
 584         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 585         diagnostic: BuiltinLintDiagnostics,
 586     ) {
 587         self.lookup(lint, span, |lint| {
 588             // We first generate a blank diagnostic.
 589             let mut db = lint.build("");
 590
 591             // Now, set up surrounding context.
 592             let sess = self.sess();
 593             match diagnostic {
 594                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
 595                     let spans: Vec<_> = content
 596                         .char_indices()
 597                         .filter_map(|(i, c)| {
 598                             TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
 599                                 let lo = span.lo() + BytePos(2 + i as u32);
 600                                 (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
 601                             })
 602                         })
 603                         .collect();
 604                     let (an, s) = match spans.len() {
 605                         1 => ("an ", ""),
 606                         _ => ("", "s"),
 607                     };
 608                     db.span_label(span, &format!(
 609                         "this comment contains {}invisible unicode text flow control codepoint{}",
 610                         an,
 611                         s,
 612                     ));
 613                     for (c, span) in &spans {
 614                         db.span_label(*span, format!("{:?}", c));
 615                     }
 616                     db.note(
 617                         "these kind of unicode codepoints change the way text flows on \
 618                          applications that support them, but can cause confusion because they \
 619                          change the order of characters on the screen",
 620                     );
 621                     if !spans.is_empty() {
 622                         db.multipart_suggestion_with_style(
 623                             "if their presence wasn't intentional, you can remove them",
 624                             spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
 625                             Applicability::MachineApplicable,
 626                             SuggestionStyle::HideCodeAlways,
 627                         );
 628                     }
 629                 },
 630                 BuiltinLintDiagnostics::Normal => (),
 631                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 632                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 633                         Ok(ref s) => {
 634                             // FIXME(Manishearth) ideally the emitting code
 635                             // can tell us whether or not this is global
 636                             let opt_colon =
 637                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 638
 639                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 640                         }
 641                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 642                     };
 643                     db.span_suggestion(span, "use `crate`", sugg, app);
 644                 }
 645                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 646                     db.span_label(
 647                         span,
 648                         "names from parent modules are not accessible without an explicit import",
 649                     );
 650                 }
 651                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 652                     span_def,
 653                 ) => {
 654                     db.span_note(span_def, "the macro is defined here");
 655                 }
 656                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 657                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 658                 }
 659                 BuiltinLintDiagnostics::UnusedImports(message, replaces, in_test_module) => {
 660                     if !replaces.is_empty() {
 661                         db.tool_only_multipart_suggestion(
 662                             &message,
 663                             replaces,
 664                             Applicability::MachineApplicable,
 665                         );
 666                     }
 667
 668                     if let Some(span) = in_test_module {
 669                         let def_span = self.sess().source_map().guess_head_span(span);
 670                         db.span_help(
 671                             span.shrink_to_lo().to(def_span),
 672                             "consider adding a `#[cfg(test)]` to the containing module",
 673                         );
 674                     }
 675                 }
 676                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 677                     for (span, is_imported) in spans {
 678                         let introduced = if is_imported { "imported" } else { "defined" };
 679                         db.span_label(
 680                             span,
 681                             format!("the item `{}` is already {} here", ident, introduced),
 682                         );
 683                     }
 684                 }
 685                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 686                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 687                 }
 688                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 689                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 690                     db.help("to document an item produced by a macro, \
 691                                   the macro must produce the documentation as part of its expansion");
 692                 }
 693                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 694                     db.span_suggestion(span, "remove `mut` from the parameter", ident.to_string(), Applicability::MachineApplicable);
 695                 }
 696                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 697                     db.span_label(span, "ABI should be specified here");
 698                     db.help(&format!("the default ABI is {}", default_abi.name()));
 699                 }
 700                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 701                     db.span_label(span, "the attribute is introduced here");
 702                 }
 703                 BuiltinLintDiagnostics::ExternDepSpec(krate, loc) => {
 704                     let json = match loc {
 705                         ExternDepSpec::Json(json) => {
 706                             db.help(&format!("remove unnecessary dependency `{}`", krate));
 707                             json
 708                         }
 709                         ExternDepSpec::Raw(raw) => {
 710                             db.help(&format!("remove unnecessary dependency `{}` at `{}`", krate, raw));
 711                             db.span_suggestion_with_style(
 712                                 DUMMY_SP,
 713                                 "raw extern location",
 714                                 raw.clone(),
 715                                 Applicability::Unspecified,
 716                                 SuggestionStyle::CompletelyHidden,
 717                             );
 718                             Json::String(raw)
 719                         }
 720                     };
 721                     db.tool_only_suggestion_with_metadata(
 722                         "json extern location",
 723                         Applicability::Unspecified,
 724                         json
 725                     );
 726                 }
 727                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 728                     db.note(&note);
 729                 }
 730                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 731                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 732                 }
 733                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 734                     db.span_label(span, "unknown prefix");
 735                     db.span_suggestion_verbose(
 736                         span.shrink_to_hi(),
 737                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 738                         " ".into(),
 739                         Applicability::MachineApplicable,
 740                     );
 741                 }
 742                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 743                     attr_name,
 744                     macro_name,
 745                     invoc_span
 746                 } => {
 747                     db.span_note(
 748                         invoc_span,
 749                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 750                     );
 751                 }
 752                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 753                     if is_trailing {
 754                         db.note("macro invocations at the end of a block are treated as expressions");
 755                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 756                     }
 757                 }
 758                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 759                     db.multipart_suggestion(
 760                         "wrap this expression in parentheses",
 761                         vec![(span.shrink_to_lo(), "(".to_string()),
 762                              (span.shrink_to_hi(), ")".to_string())],
 763                         Applicability::MachineApplicable
 764                     );
 765                 }
 766                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 767                     db.help(&help);
 768                     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");
 769                 }
 770             }
 771             // Rewrap `db`, and pass control to the user.
 772             decorate(LintDiagnosticBuilder::new(db));
 773         });
 774     }
 775
 776     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 777     // set the span in their `decorate` function (preferably using set_span).
 778     fn lookup<S: Into<MultiSpan>>(
 779         &self,
 780         lint: &'static Lint,
 781         span: Option<S>,
 782         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 783     );
 784
 785     fn struct_span_lint<S: Into<MultiSpan>>(
 786         &self,
 787         lint: &'static Lint,
 788         span: S,
 789         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 790     ) {
 791         self.lookup(lint, Some(span), decorate);
 792     }
 793     /// Emit a lint at the appropriate level, with no associated span.
 794     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 795         self.lookup(lint, None as Option<Span>, decorate);
 796     }
 797 }
 798
 799 impl<'a> EarlyContext<'a> {
 800     pub(crate) fn new(
 801         sess: &'a Session,
 802         warn_about_weird_lints: bool,
 803         lint_store: &'a LintStore,
 804         registered_tools: &'a RegisteredTools,
 805         buffered: LintBuffer,
 806     ) -> EarlyContext<'a> {
 807         EarlyContext {
 808             builder: LintLevelsBuilder::new(
 809                 sess,
 810                 warn_about_weird_lints,
 811                 lint_store,
 812                 registered_tools,
 813             ),
 814             buffered,
 815         }
 816     }
 817 }
 818
 819 impl LintContext for LateContext<'_> {
 820     type PassObject = LateLintPassObject;
 821
 822     /// Gets the overall compiler `Session` object.
 823     fn sess(&self) -> &Session {
 824         &self.tcx.sess
 825     }
 826
 827     fn lints(&self) -> &LintStore {
 828         &*self.lint_store
 829     }
 830
 831     fn lookup<S: Into<MultiSpan>>(
 832         &self,
 833         lint: &'static Lint,
 834         span: Option<S>,
 835         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 836     ) {
 837         let hir_id = self.last_node_with_lint_attrs;
 838
 839         match span {
 840             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 841             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 842         }
 843     }
 844 }
 845
 846 impl LintContext for EarlyContext<'_> {
 847     type PassObject = EarlyLintPassObject;
 848
 849     /// Gets the overall compiler `Session` object.
 850     fn sess(&self) -> &Session {
 851         &self.builder.sess()
 852     }
 853
 854     fn lints(&self) -> &LintStore {
 855         self.builder.lint_store()
 856     }
 857
 858     fn lookup<S: Into<MultiSpan>>(
 859         &self,
 860         lint: &'static Lint,
 861         span: Option<S>,
 862         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 863     ) {
 864         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 865     }
 866 }
 867
 868 impl<'tcx> LateContext<'tcx> {
 869     /// Gets the type-checking results for the current body,
 870     /// or `None` if outside a body.
 871     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 872         self.cached_typeck_results.get().or_else(|| {
 873             self.enclosing_body.map(|body| {
 874                 let typeck_results = self.tcx.typeck_body(body);
 875                 self.cached_typeck_results.set(Some(typeck_results));
 876                 typeck_results
 877             })
 878         })
 879     }
 880
 881     /// Gets the type-checking results for the current body.
 882     /// As this will ICE if called outside bodies, only call when working with
 883     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 884     #[track_caller]
 885     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 886         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 887     }
 888
 889     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 890     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 891     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 892     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 893         match *qpath {
 894             hir::QPath::Resolved(_, ref path) => path.res,
 895             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 896                 .maybe_typeck_results()
 897                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
 898                 .or_else(|| {
 899                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
 900                         Some(self.tcx.typeck(id.owner))
 901                     } else {
 902                         None
 903                     }
 904                 })
 905                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 906                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 907         }
 908     }
 909
 910     /// Check if a `DefId`'s path matches the given absolute type path usage.
 911     ///
 912     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
 913     /// inherent `impl` blocks are matched with the name of the type.
 914     ///
 915     /// Instead of using this method, it is often preferable to instead use
 916     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 917     /// as paths get invalidated if the target definition moves.
 918     ///
 919     /// # Examples
 920     ///
 921     /// ```rust,ignore (no context or def id available)
 922     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 923     ///     // The given `def_id` is that of an `Option` type
 924     /// }
 925     /// ```
 926     ///
 927     /// Used by clippy, but should be replaced by diagnostic items eventually.
 928     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 929         let names = self.get_def_path(def_id);
 930
 931         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
 932     }
 933
 934     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 935     ///
 936     /// # Examples
 937     ///
 938     /// ```rust,ignore (no context or def id available)
 939     /// let def_path = cx.get_def_path(def_id);
 940     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 941     ///     // The given `def_id` is that of an `Option` type
 942     /// }
 943     /// ```
 944     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 945         pub struct AbsolutePathPrinter<'tcx> {
 946             pub tcx: TyCtxt<'tcx>,
 947         }
 948
 949         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 950             type Error = !;
 951
 952             type Path = Vec<Symbol>;
 953             type Region = ();
 954             type Type = ();
 955             type DynExistential = ();
 956             type Const = ();
 957
 958             fn tcx(&self) -> TyCtxt<'tcx> {
 959                 self.tcx
 960             }
 961
 962             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 963                 Ok(())
 964             }
 965
 966             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 967                 Ok(())
 968             }
 969
 970             fn print_dyn_existential(
 971                 self,
 972                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
 973             ) -> Result<Self::DynExistential, Self::Error> {
 974                 Ok(())
 975             }
 976
 977             fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 978                 Ok(())
 979             }
 980
 981             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 982                 Ok(vec![self.tcx.crate_name(cnum)])
 983             }
 984
 985             fn path_qualified(
 986                 self,
 987                 self_ty: Ty<'tcx>,
 988                 trait_ref: Option<ty::TraitRef<'tcx>>,
 989             ) -> Result<Self::Path, Self::Error> {
 990                 if trait_ref.is_none() {
 991                     if let ty::Adt(def, substs) = self_ty.kind() {
 992                         return self.print_def_path(def.did, substs);
 993                     }
 994                 }
 995
 996                 // This shouldn't ever be needed, but just in case:
 997                 with_no_trimmed_paths(|| {
 998                     Ok(vec![match trait_ref {
 999                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1000                         None => Symbol::intern(&format!("<{}>", self_ty)),
1001                     }])
1002                 })
1003             }
1004
1005             fn path_append_impl(
1006                 self,
1007                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1008                 _disambiguated_data: &DisambiguatedDefPathData,
1009                 self_ty: Ty<'tcx>,
1010                 trait_ref: Option<ty::TraitRef<'tcx>>,
1011             ) -> Result<Self::Path, Self::Error> {
1012                 let mut path = print_prefix(self)?;
1013
1014                 // This shouldn't ever be needed, but just in case:
1015                 path.push(match trait_ref {
1016                     Some(trait_ref) => with_no_trimmed_paths(|| {
1017                         Symbol::intern(&format!(
1018                             "<impl {} for {}>",
1019                             trait_ref.print_only_trait_path(),
1020                             self_ty
1021                         ))
1022                     }),
1023                     None => {
1024                         with_no_trimmed_paths(|| Symbol::intern(&format!("<impl {}>", self_ty)))
1025                     }
1026                 });
1027
1028                 Ok(path)
1029             }
1030
1031             fn path_append(
1032                 self,
1033                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1034                 disambiguated_data: &DisambiguatedDefPathData,
1035             ) -> Result<Self::Path, Self::Error> {
1036                 let mut path = print_prefix(self)?;
1037
1038                 // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1039                 if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1040                     return Ok(path);
1041                 }
1042
1043                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1044                 Ok(path)
1045             }
1046
1047             fn path_generic_args(
1048                 self,
1049                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1050                 _args: &[GenericArg<'tcx>],
1051             ) -> Result<Self::Path, Self::Error> {
1052                 print_prefix(self)
1053             }
1054         }
1055
1056         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1057     }
1058 }
1059
1060 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1061     #[inline]
1062     fn data_layout(&self) -> &abi::TargetDataLayout {
1063         &self.tcx.data_layout
1064     }
1065 }
1066
1067 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1068     #[inline]
1069     fn tcx(&self) -> TyCtxt<'tcx> {
1070         self.tcx
1071     }
1072 }
1073
1074 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1075     #[inline]
1076     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1077         self.param_env
1078     }
1079 }
1080
1081 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1082     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1083
1084     #[inline]
1085     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1086         err
1087     }
1088 }
1089
1090 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1091     match lint_name.split_once("::") {
1092         Some((tool_name, lint_name)) => {
1093             let tool_name = Symbol::intern(tool_name);
1094
1095             (Some(tool_name), lint_name)
1096         }
1097         None => (None, lint_name),
1098     }
1099 }