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 as ast;
  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, Applicability};
  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, TyAndLayout};
  33 use rustc_middle::ty::print::with_no_trimmed_paths;
  34 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, Ty, TyCtxt};
  35 use rustc_session::lint::BuiltinLintDiagnostics;
  36 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  37 use rustc_session::Session;
  38 use rustc_session::SessionLintStore;
  39 use rustc_span::lev_distance::find_best_match_for_name;
  40 use rustc_span::{symbol::Symbol, MultiSpan, Span, DUMMY_SP};
  41 use rustc_target::abi::LayoutOf;
  42 use tracing::debug;
  43
  44 use std::cell::Cell;
  45 use std::slice;
  46
  47 /// Information about the registered lints.
  48 ///
  49 /// This is basically the subset of `Context` that we can
  50 /// build early in the compile pipeline.
  51 pub struct LintStore {
  52     /// Registered lints.
  53     lints: Vec<&'static Lint>,
  54
  55     /// Constructor functions for each variety of lint pass.
  56     ///
  57     /// These should only be called once, but since we want to avoid locks or
  58     /// interior mutability, we don't enforce this (and lints should, in theory,
  59     /// be compatible with being constructed more than once, though not
  60     /// necessarily in a sane manner. This is safe though.)
  61     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  62     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  63     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  64     /// This is unique in that we construct them per-module, so not once.
  65     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  66
  67     /// Lints indexed by name.
  68     by_name: FxHashMap<String, TargetLint>,
  69
  70     /// Map of registered lint groups to what lints they expand to.
  71     lint_groups: FxHashMap<&'static str, LintGroup>,
  72 }
  73
  74 impl SessionLintStore for LintStore {
  75     fn name_to_lint(&self, lint_name: &str) -> LintId {
  76         let lints = self
  77             .find_lints(lint_name)
  78             .unwrap_or_else(|_| panic!("Failed to find lint with name `{}`", lint_name));
  79
  80         if let &[lint] = lints.as_slice() {
  81             return lint;
  82         } else {
  83             panic!("Found mutliple lints with name `{}`: {:?}", lint_name, lints);
  84         }
  85     }
  86 }
  87
  88 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  89 enum TargetLint {
  90     /// A direct lint target
  91     Id(LintId),
  92
  93     /// Temporary renaming, used for easing migration pain; see #16545
  94     Renamed(String, LintId),
  95
  96     /// Lint with this name existed previously, but has been removed/deprecated.
  97     /// The string argument is the reason for removal.
  98     Removed(String),
  99 }
 100
 101 pub enum FindLintError {
 102     NotFound,
 103     Removed,
 104 }
 105
 106 struct LintAlias {
 107     name: &'static str,
 108     /// Whether deprecation warnings should be suppressed for this alias.
 109     silent: bool,
 110 }
 111
 112 struct LintGroup {
 113     lint_ids: Vec<LintId>,
 114     from_plugin: bool,
 115     depr: Option<LintAlias>,
 116 }
 117
 118 pub enum CheckLintNameResult<'a> {
 119     Ok(&'a [LintId]),
 120     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 121     NoLint(Option<Symbol>),
 122     /// The lint is either renamed or removed. This is the warning
 123     /// message, and an optional new name (`None` if removed).
 124     Warning(String, Option<String>),
 125     /// The lint is from a tool. If the Option is None, then either
 126     /// the lint does not exist in the tool or the code was not
 127     /// compiled with the tool and therefore the lint was never
 128     /// added to the `LintStore`. Otherwise the `LintId` will be
 129     /// returned as if it where a rustc lint.
 130     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 131 }
 132
 133 impl LintStore {
 134     pub fn new() -> LintStore {
 135         LintStore {
 136             lints: vec![],
 137             pre_expansion_passes: vec![],
 138             early_passes: vec![],
 139             late_passes: vec![],
 140             late_module_passes: vec![],
 141             by_name: Default::default(),
 142             lint_groups: Default::default(),
 143         }
 144     }
 145
 146     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 147         &self.lints
 148     }
 149
 150     pub fn get_lint_groups<'t>(&'t self) -> Vec<(&'static str, Vec<LintId>, bool)> {
 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             .collect()
 161     }
 162
 163     pub fn register_early_pass(
 164         &mut self,
 165         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 166     ) {
 167         self.early_passes.push(Box::new(pass));
 168     }
 169
 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 { edition, .. }) = lint.future_incompatible {
 202                 if let Some(edition) = 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                 }
 213
 214                 self.lint_groups
 215                     .entry("future_incompatible")
 216                     .or_insert(LintGroup {
 217                         lint_ids: vec![],
 218                         from_plugin: lint.is_plugin,
 219                         depr: None,
 220                     })
 221                     .lint_ids
 222                     .push(id);
 223             }
 224         }
 225     }
 226
 227     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 228         self.lint_groups.insert(
 229             alias,
 230             LintGroup {
 231                 lint_ids: vec![],
 232                 from_plugin: false,
 233                 depr: Some(LintAlias { name: lint_name, silent: true }),
 234             },
 235         );
 236     }
 237
 238     pub fn register_group(
 239         &mut self,
 240         from_plugin: bool,
 241         name: &'static str,
 242         deprecated_name: Option<&'static str>,
 243         to: Vec<LintId>,
 244     ) {
 245         let new = self
 246             .lint_groups
 247             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 248             .is_none();
 249         if let Some(deprecated) = deprecated_name {
 250             self.lint_groups.insert(
 251                 deprecated,
 252                 LintGroup {
 253                     lint_ids: vec![],
 254                     from_plugin,
 255                     depr: Some(LintAlias { name, silent: false }),
 256                 },
 257             );
 258         }
 259
 260         if !new {
 261             bug!("duplicate specification of lint group {}", name);
 262         }
 263     }
 264
 265     #[track_caller]
 266     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 267         let target = match self.by_name.get(new_name) {
 268             Some(&Id(lint_id)) => lint_id,
 269             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 270         };
 271         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 272     }
 273
 274     pub fn register_removed(&mut self, name: &str, reason: &str) {
 275         self.by_name.insert(name.into(), Removed(reason.into()));
 276     }
 277
 278     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 279         match self.by_name.get(lint_name) {
 280             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 281             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 282             Some(&Removed(_)) => Err(FindLintError::Removed),
 283             None => loop {
 284                 return match self.lint_groups.get(lint_name) {
 285                     Some(LintGroup { lint_ids, depr, .. }) => {
 286                         if let Some(LintAlias { name, .. }) = depr {
 287                             lint_name = name;
 288                             continue;
 289                         }
 290                         Ok(lint_ids.clone())
 291                     }
 292                     None => Err(FindLintError::Removed),
 293                 };
 294             },
 295         }
 296     }
 297
 298     /// Checks the validity of lint names derived from the command line
 299     pub fn check_lint_name_cmdline(&self, sess: &Session, lint_name: &str, level: Level) {
 300         let db = match self.check_lint_name(lint_name, None) {
 301             CheckLintNameResult::Ok(_) => None,
 302             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 303             CheckLintNameResult::NoLint(suggestion) => {
 304                 let mut err =
 305                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 306
 307                 if let Some(suggestion) = suggestion {
 308                     err.help(&format!("did you mean: `{}`", suggestion));
 309                 }
 310
 311                 Some(err)
 312             }
 313             CheckLintNameResult::Tool(result) => match result {
 314                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 315                     "lint name `{}` is deprecated \
 316                      and does not have an effect anymore. \
 317                      Use: {}",
 318                     lint_name, new_name
 319                 ))),
 320                 _ => None,
 321             },
 322         };
 323
 324         if let Some(mut db) = db {
 325             let msg = format!(
 326                 "requested on the command line with `{} {}`",
 327                 match level {
 328                     Level::Allow => "-A",
 329                     Level::Warn => "-W",
 330                     Level::Deny => "-D",
 331                     Level::Forbid => "-F",
 332                 },
 333                 lint_name
 334             );
 335             db.note(&msg);
 336             db.emit();
 337         }
 338     }
 339
 340     /// True if this symbol represents a lint group name.
 341     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 342         debug!(
 343             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 344             lint_name,
 345             self.lint_groups.keys().collect::<Vec<_>>()
 346         );
 347         let lint_name_str = &*lint_name.as_str();
 348         self.lint_groups.contains_key(&lint_name_str) || {
 349             let warnings_name_str = crate::WARNINGS.name_lower();
 350             lint_name_str == &*warnings_name_str
 351         }
 352     }
 353
 354     /// Checks the name of a lint for its existence, and whether it was
 355     /// renamed or removed. Generates a DiagnosticBuilder containing a
 356     /// warning for renamed and removed lints. This is over both lint
 357     /// names from attributes and those passed on the command line. Since
 358     /// it emits non-fatal warnings and there are *two* lint passes that
 359     /// inspect attributes, this is only run from the late pass to avoid
 360     /// printing duplicate warnings.
 361     pub fn check_lint_name(
 362         &self,
 363         lint_name: &str,
 364         tool_name: Option<Symbol>,
 365     ) -> CheckLintNameResult<'_> {
 366         let complete_name = if let Some(tool_name) = tool_name {
 367             format!("{}::{}", tool_name, lint_name)
 368         } else {
 369             lint_name.to_string()
 370         };
 371         // If the lint was scoped with `tool::` check if the tool lint exists
 372         if let Some(tool_name) = tool_name {
 373             match self.by_name.get(&complete_name) {
 374                 None => match self.lint_groups.get(&*complete_name) {
 375                     // If the lint isn't registered, there are two possibilities:
 376                     None => {
 377                         // 1. The tool is currently running, so this lint really doesn't exist.
 378                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 379                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 380                         let tool_prefix = format!("{}::", tool_name);
 381                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 382                             self.no_lint_suggestion(&complete_name)
 383                         } else {
 384                             // 2. The tool isn't currently running, so no lints will be registered.
 385                             // To avoid giving a false positive, ignore all unknown lints.
 386                             CheckLintNameResult::Tool(Err((None, String::new())))
 387                         };
 388                     }
 389                     Some(LintGroup { lint_ids, .. }) => {
 390                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 391                     }
 392                 },
 393                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 394                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 395                 // to treat tool_lints and rustc lints different and can use the code below.
 396                 _ => {}
 397             }
 398         }
 399         match self.by_name.get(&complete_name) {
 400             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 401                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 402                 Some(new_name.to_owned()),
 403             ),
 404             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 405                 format!("lint `{}` has been removed: {}", complete_name, reason),
 406                 None,
 407             ),
 408             None => match self.lint_groups.get(&*complete_name) {
 409                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 410                 // variant of this lint
 411                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 412                 Some(LintGroup { lint_ids, depr, .. }) => {
 413                     // Check if the lint group name is deprecated
 414                     if let Some(LintAlias { name, silent }) = depr {
 415                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 416                         return if *silent {
 417                             CheckLintNameResult::Ok(&lint_ids)
 418                         } else {
 419                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 420                         };
 421                     }
 422                     CheckLintNameResult::Ok(&lint_ids)
 423                 }
 424             },
 425             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 426         }
 427     }
 428
 429     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 430         let name_lower = lint_name.to_lowercase();
 431         let symbols =
 432             self.get_lints().iter().map(|l| Symbol::intern(&l.name_lower())).collect::<Vec<_>>();
 433
 434         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 435             // First check if the lint name is (partly) in upper case instead of lower case...
 436             CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)))
 437         } else {
 438             // ...if not, search for lints with a similar name
 439             let suggestion = find_best_match_for_name(&symbols, Symbol::intern(&name_lower), None);
 440             CheckLintNameResult::NoLint(suggestion)
 441         }
 442     }
 443
 444     fn check_tool_name_for_backwards_compat(
 445         &self,
 446         lint_name: &str,
 447         tool_name: &str,
 448     ) -> CheckLintNameResult<'_> {
 449         let complete_name = format!("{}::{}", tool_name, lint_name);
 450         match self.by_name.get(&complete_name) {
 451             None => match self.lint_groups.get(&*complete_name) {
 452                 // Now we are sure, that this lint exists nowhere
 453                 None => self.no_lint_suggestion(lint_name),
 454                 Some(LintGroup { lint_ids, depr, .. }) => {
 455                     // Reaching this would be weird, but let's cover this case anyway
 456                     if let Some(LintAlias { name, silent }) = depr {
 457                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 458                         return if *silent {
 459                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 460                         } else {
 461                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 462                         };
 463                     }
 464                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 465                 }
 466             },
 467             Some(&Id(ref id)) => {
 468                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 469             }
 470             _ => CheckLintNameResult::NoLint(None),
 471         }
 472     }
 473 }
 474
 475 /// Context for lint checking after type checking.
 476 pub struct LateContext<'tcx> {
 477     /// Type context we're checking in.
 478     pub tcx: TyCtxt<'tcx>,
 479
 480     /// Current body, or `None` if outside a body.
 481     pub enclosing_body: Option<hir::BodyId>,
 482
 483     /// Type-checking results for the current body. Access using the `typeck_results`
 484     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 485     // FIXME(eddyb) move all the code accessing internal fields like this,
 486     // to this module, to avoid exposing it to lint logic.
 487     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 488
 489     /// Parameter environment for the item we are in.
 490     pub param_env: ty::ParamEnv<'tcx>,
 491
 492     /// Items accessible from the crate being checked.
 493     pub access_levels: &'tcx AccessLevels,
 494
 495     /// The store of registered lints and the lint levels.
 496     pub lint_store: &'tcx LintStore,
 497
 498     pub last_node_with_lint_attrs: hir::HirId,
 499
 500     /// Generic type parameters in scope for the item we are in.
 501     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 502
 503     /// We are only looking at one module
 504     pub only_module: bool,
 505 }
 506
 507 /// Context for lint checking of the AST, after expansion, before lowering to
 508 /// HIR.
 509 pub struct EarlyContext<'a> {
 510     /// Type context we're checking in.
 511     pub sess: &'a Session,
 512
 513     /// The crate being checked.
 514     pub krate: &'a ast::Crate,
 515
 516     pub builder: LintLevelsBuilder<'a>,
 517
 518     /// The store of registered lints and the lint levels.
 519     pub lint_store: &'a LintStore,
 520
 521     pub buffered: LintBuffer,
 522 }
 523
 524 pub trait LintPassObject: Sized {}
 525
 526 impl LintPassObject for EarlyLintPassObject {}
 527
 528 impl LintPassObject for LateLintPassObject {}
 529
 530 pub trait LintContext: Sized {
 531     type PassObject: LintPassObject;
 532
 533     fn sess(&self) -> &Session;
 534     fn lints(&self) -> &LintStore;
 535
 536     fn lookup_with_diagnostics(
 537         &self,
 538         lint: &'static Lint,
 539         span: Option<impl Into<MultiSpan>>,
 540         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 541         diagnostic: BuiltinLintDiagnostics,
 542     ) {
 543         self.lookup(lint, span, |lint| {
 544             // We first generate a blank diagnostic.
 545             let mut db = lint.build("");
 546
 547             // Now, set up surrounding context.
 548             let sess = self.sess();
 549             match diagnostic {
 550                 BuiltinLintDiagnostics::Normal => (),
 551                 BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 552                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 553                         Ok(s) if is_global => {
 554                             (format!("dyn ({})", s), Applicability::MachineApplicable)
 555                         }
 556                         Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 557                         Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
 558                     };
 559                     db.span_suggestion(span, "use `dyn`", sugg, app);
 560                 }
 561                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 562                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 563                         Ok(ref s) => {
 564                             // FIXME(Manishearth) ideally the emitting code
 565                             // can tell us whether or not this is global
 566                             let opt_colon =
 567                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 568
 569                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 570                         }
 571                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 572                     };
 573                     db.span_suggestion(span, "use `crate`", sugg, app);
 574                 }
 575                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 576                     db.span_label(
 577                         span,
 578                         "names from parent modules are not accessible without an explicit import",
 579                     );
 580                 }
 581                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 582                     span_def,
 583                 ) => {
 584                     db.span_note(span_def, "the macro is defined here");
 585                 }
 586                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 587                     n,
 588                     path_span,
 589                     incl_angl_brckt,
 590                     insertion_span,
 591                     anon_lts,
 592                 ) => {
 593                     add_elided_lifetime_in_path_suggestion(
 594                         sess.source_map(),
 595                         &mut db,
 596                         n,
 597                         path_span,
 598                         incl_angl_brckt,
 599                         insertion_span,
 600                         anon_lts,
 601                     );
 602                 }
 603                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 604                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 605                 }
 606                 BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
 607                     if !replaces.is_empty() {
 608                         db.tool_only_multipart_suggestion(
 609                             &message,
 610                             replaces,
 611                             Applicability::MachineApplicable,
 612                         );
 613                     }
 614                 }
 615                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 616                     for (span, is_imported) in spans {
 617                         let introduced = if is_imported { "imported" } else { "defined" };
 618                         db.span_label(
 619                             span,
 620                             format!("the item `{}` is already {} here", ident, introduced),
 621                         );
 622                     }
 623                 }
 624                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 625                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 626                 }
 627                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 628                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 629                     db.help("to document an item produced by a macro, \
 630                                   the macro must produce the documentation as part of its expansion");
 631                 }
 632                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 633                     db.span_suggestion(span, "remove `mut` from the parameter", ident.to_string(), Applicability::MachineApplicable);
 634                 }
 635                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 636                     db.span_label(span, "ABI should be specified here");
 637                     db.help(&format!("the default ABI is {}", default_abi.name()));
 638                 }
 639             }
 640             // Rewrap `db`, and pass control to the user.
 641             decorate(LintDiagnosticBuilder::new(db));
 642         });
 643     }
 644
 645     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 646     // set the span in their `decorate` function (preferably using set_span).
 647     fn lookup<S: Into<MultiSpan>>(
 648         &self,
 649         lint: &'static Lint,
 650         span: Option<S>,
 651         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 652     );
 653
 654     fn struct_span_lint<S: Into<MultiSpan>>(
 655         &self,
 656         lint: &'static Lint,
 657         span: S,
 658         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 659     ) {
 660         self.lookup(lint, Some(span), decorate);
 661     }
 662     /// Emit a lint at the appropriate level, with no associated span.
 663     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 664         self.lookup(lint, None as Option<Span>, decorate);
 665     }
 666 }
 667
 668 impl<'a> EarlyContext<'a> {
 669     pub fn new(
 670         sess: &'a Session,
 671         lint_store: &'a LintStore,
 672         krate: &'a ast::Crate,
 673         buffered: LintBuffer,
 674         warn_about_weird_lints: bool,
 675     ) -> EarlyContext<'a> {
 676         EarlyContext {
 677             sess,
 678             krate,
 679             lint_store,
 680             builder: LintLevelsBuilder::new(sess, warn_about_weird_lints, lint_store),
 681             buffered,
 682         }
 683     }
 684 }
 685
 686 impl LintContext for LateContext<'_> {
 687     type PassObject = LateLintPassObject;
 688
 689     /// Gets the overall compiler `Session` object.
 690     fn sess(&self) -> &Session {
 691         &self.tcx.sess
 692     }
 693
 694     fn lints(&self) -> &LintStore {
 695         &*self.lint_store
 696     }
 697
 698     fn lookup<S: Into<MultiSpan>>(
 699         &self,
 700         lint: &'static Lint,
 701         span: Option<S>,
 702         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 703     ) {
 704         let hir_id = self.last_node_with_lint_attrs;
 705
 706         match span {
 707             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 708             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 709         }
 710     }
 711 }
 712
 713 impl LintContext for EarlyContext<'_> {
 714     type PassObject = EarlyLintPassObject;
 715
 716     /// Gets the overall compiler `Session` object.
 717     fn sess(&self) -> &Session {
 718         &self.sess
 719     }
 720
 721     fn lints(&self) -> &LintStore {
 722         &*self.lint_store
 723     }
 724
 725     fn lookup<S: Into<MultiSpan>>(
 726         &self,
 727         lint: &'static Lint,
 728         span: Option<S>,
 729         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 730     ) {
 731         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 732     }
 733 }
 734
 735 impl<'tcx> LateContext<'tcx> {
 736     /// Gets the type-checking results for the current body,
 737     /// or `None` if outside a body.
 738     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 739         self.cached_typeck_results.get().or_else(|| {
 740             self.enclosing_body.map(|body| {
 741                 let typeck_results = self.tcx.typeck_body(body);
 742                 self.cached_typeck_results.set(Some(typeck_results));
 743                 typeck_results
 744             })
 745         })
 746     }
 747
 748     /// Gets the type-checking results for the current body.
 749     /// As this will ICE if called outside bodies, only call when working with
 750     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 751     #[track_caller]
 752     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 753         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 754     }
 755
 756     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 757     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 758     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 759     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 760         match *qpath {
 761             hir::QPath::Resolved(_, ref path) => path.res,
 762             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 763                 .maybe_typeck_results()
 764                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
 765                 .or_else(|| {
 766                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
 767                         Some(self.tcx.typeck(id.owner))
 768                     } else {
 769                         None
 770                     }
 771                 })
 772                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 773                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 774         }
 775     }
 776
 777     /// Check if a `DefId`'s path matches the given absolute type path usage.
 778     ///
 779     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
 780     /// inherent `impl` blocks are matched with the name of the type.
 781     ///
 782     /// Instead of using this method, it is often preferable to instead use
 783     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 784     /// as paths get invalidated if the target definition moves.
 785     ///
 786     /// # Examples
 787     ///
 788     /// ```rust,ignore (no context or def id available)
 789     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 790     ///     // The given `def_id` is that of an `Option` type
 791     /// }
 792     /// ```
 793     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 794         let names = self.get_def_path(def_id);
 795
 796         names.len() == path.len() && names.into_iter().zip(path.iter()).all(|(a, &b)| a == b)
 797     }
 798
 799     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 800     ///
 801     /// # Examples
 802     ///
 803     /// ```rust,ignore (no context or def id available)
 804     /// let def_path = cx.get_def_path(def_id);
 805     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 806     ///     // The given `def_id` is that of an `Option` type
 807     /// }
 808     /// ```
 809     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 810         pub struct AbsolutePathPrinter<'tcx> {
 811             pub tcx: TyCtxt<'tcx>,
 812         }
 813
 814         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 815             type Error = !;
 816
 817             type Path = Vec<Symbol>;
 818             type Region = ();
 819             type Type = ();
 820             type DynExistential = ();
 821             type Const = ();
 822
 823             fn tcx(&self) -> TyCtxt<'tcx> {
 824                 self.tcx
 825             }
 826
 827             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 828                 Ok(())
 829             }
 830
 831             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 832                 Ok(())
 833             }
 834
 835             fn print_dyn_existential(
 836                 self,
 837                 _predicates: &'tcx ty::List<ty::Binder<ty::ExistentialPredicate<'tcx>>>,
 838             ) -> Result<Self::DynExistential, Self::Error> {
 839                 Ok(())
 840             }
 841
 842             fn print_const(self, _ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 843                 Ok(())
 844             }
 845
 846             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 847                 Ok(vec![self.tcx.original_crate_name(cnum)])
 848             }
 849
 850             fn path_qualified(
 851                 self,
 852                 self_ty: Ty<'tcx>,
 853                 trait_ref: Option<ty::TraitRef<'tcx>>,
 854             ) -> Result<Self::Path, Self::Error> {
 855                 if trait_ref.is_none() {
 856                     if let ty::Adt(def, substs) = self_ty.kind() {
 857                         return self.print_def_path(def.did, substs);
 858                     }
 859                 }
 860
 861                 // This shouldn't ever be needed, but just in case:
 862                 with_no_trimmed_paths(|| {
 863                     Ok(vec![match trait_ref {
 864                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
 865                         None => Symbol::intern(&format!("<{}>", self_ty)),
 866                     }])
 867                 })
 868             }
 869
 870             fn path_append_impl(
 871                 self,
 872                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 873                 _disambiguated_data: &DisambiguatedDefPathData,
 874                 self_ty: Ty<'tcx>,
 875                 trait_ref: Option<ty::TraitRef<'tcx>>,
 876             ) -> Result<Self::Path, Self::Error> {
 877                 let mut path = print_prefix(self)?;
 878
 879                 // This shouldn't ever be needed, but just in case:
 880                 path.push(match trait_ref {
 881                     Some(trait_ref) => with_no_trimmed_paths(|| {
 882                         Symbol::intern(&format!(
 883                             "<impl {} for {}>",
 884                             trait_ref.print_only_trait_path(),
 885                             self_ty
 886                         ))
 887                     }),
 888                     None => {
 889                         with_no_trimmed_paths(|| Symbol::intern(&format!("<impl {}>", self_ty)))
 890                     }
 891                 });
 892
 893                 Ok(path)
 894             }
 895
 896             fn path_append(
 897                 self,
 898                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 899                 disambiguated_data: &DisambiguatedDefPathData,
 900             ) -> Result<Self::Path, Self::Error> {
 901                 let mut path = print_prefix(self)?;
 902
 903                 // Skip `::{{constructor}}` on tuple/unit structs.
 904                 if let DefPathData::Ctor = disambiguated_data.data {
 905                     return Ok(path);
 906                 }
 907
 908                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
 909                 Ok(path)
 910             }
 911
 912             fn path_generic_args(
 913                 self,
 914                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 915                 _args: &[GenericArg<'tcx>],
 916             ) -> Result<Self::Path, Self::Error> {
 917                 print_prefix(self)
 918             }
 919         }
 920
 921         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
 922     }
 923 }
 924
 925 impl<'tcx> LayoutOf for LateContext<'tcx> {
 926     type Ty = Ty<'tcx>;
 927     type TyAndLayout = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 928
 929     fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyAndLayout {
 930         self.tcx.layout_of(self.param_env.and(ty))
 931     }
 932 }