src/librustc_lint/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_ast::util::lev_distance::find_best_match_for_name;
  23 use rustc_data_structures::fx::FxHashMap;
  24 use rustc_data_structures::sync;
  25 use rustc_errors::{struct_span_err, Applicability};
  26 use rustc_hir as hir;
  27 use rustc_hir::def::Res;
  28 use rustc_hir::def_id::{CrateNum, DefId};
  29 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  30 use rustc_middle::lint::LintDiagnosticBuilder;
  31 use rustc_middle::middle::privacy::AccessLevels;
  32 use rustc_middle::middle::stability;
  33 use rustc_middle::ty::layout::{LayoutError, TyAndLayout};
  34 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, Ty, TyCtxt};
  35 use rustc_session::lint::{add_elided_lifetime_in_path_suggestion, BuiltinLintDiagnostics};
  36 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  37 use rustc_session::Session;
  38 use rustc_span::{symbol::Symbol, MultiSpan, Span, DUMMY_SP};
  39 use rustc_target::abi::LayoutOf;
  40
  41 use std::cell::Cell;
  42 use std::slice;
  43
  44 /// Information about the registered lints.
  45 ///
  46 /// This is basically the subset of `Context` that we can
  47 /// build early in the compile pipeline.
  48 pub struct LintStore {
  49     /// Registered lints.
  50     lints: Vec<&'static Lint>,
  51
  52     /// Constructor functions for each variety of lint pass.
  53     ///
  54     /// These should only be called once, but since we want to avoid locks or
  55     /// interior mutability, we don't enforce this (and lints should, in theory,
  56     /// be compatible with being constructed more than once, though not
  57     /// necessarily in a sane manner. This is safe though.)
  58     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  59     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  60     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  61     /// This is unique in that we construct them per-module, so not once.
  62     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  63
  64     /// Lints indexed by name.
  65     by_name: FxHashMap<String, TargetLint>,
  66
  67     /// Map of registered lint groups to what lints they expand to.
  68     lint_groups: FxHashMap<&'static str, LintGroup>,
  69 }
  70
  71 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  72 enum TargetLint {
  73     /// A direct lint target
  74     Id(LintId),
  75
  76     /// Temporary renaming, used for easing migration pain; see #16545
  77     Renamed(String, LintId),
  78
  79     /// Lint with this name existed previously, but has been removed/deprecated.
  80     /// The string argument is the reason for removal.
  81     Removed(String),
  82 }
  83
  84 pub enum FindLintError {
  85     NotFound,
  86     Removed,
  87 }
  88
  89 struct LintAlias {
  90     name: &'static str,
  91     /// Whether deprecation warnings should be suppressed for this alias.
  92     silent: bool,
  93 }
  94
  95 struct LintGroup {
  96     lint_ids: Vec<LintId>,
  97     from_plugin: bool,
  98     depr: Option<LintAlias>,
  99 }
 100
 101 pub enum CheckLintNameResult<'a> {
 102     Ok(&'a [LintId]),
 103     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 104     NoLint(Option<Symbol>),
 105     /// The lint is either renamed or removed. This is the warning
 106     /// message, and an optional new name (`None` if removed).
 107     Warning(String, Option<String>),
 108     /// The lint is from a tool. If the Option is None, then either
 109     /// the lint does not exist in the tool or the code was not
 110     /// compiled with the tool and therefore the lint was never
 111     /// added to the `LintStore`. Otherwise the `LintId` will be
 112     /// returned as if it where a rustc lint.
 113     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 114 }
 115
 116 impl LintStore {
 117     pub fn new() -> LintStore {
 118         LintStore {
 119             lints: vec![],
 120             pre_expansion_passes: vec![],
 121             early_passes: vec![],
 122             late_passes: vec![],
 123             late_module_passes: vec![],
 124             by_name: Default::default(),
 125             lint_groups: Default::default(),
 126         }
 127     }
 128
 129     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 130         &self.lints
 131     }
 132
 133     pub fn get_lint_groups<'t>(&'t self) -> Vec<(&'static str, Vec<LintId>, bool)> {
 134         self.lint_groups
 135             .iter()
 136             .filter(|(_, LintGroup { depr, .. })| {
 137                 // Don't display deprecated lint groups.
 138                 depr.is_none()
 139             })
 140             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 141                 (*k, lint_ids.clone(), *from_plugin)
 142             })
 143             .collect()
 144     }
 145
 146     pub fn register_early_pass(
 147         &mut self,
 148         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 149     ) {
 150         self.early_passes.push(Box::new(pass));
 151     }
 152
 153     pub fn register_pre_expansion_pass(
 154         &mut self,
 155         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 156     ) {
 157         self.pre_expansion_passes.push(Box::new(pass));
 158     }
 159
 160     pub fn register_late_pass(
 161         &mut self,
 162         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 163     ) {
 164         self.late_passes.push(Box::new(pass));
 165     }
 166
 167     pub fn register_late_mod_pass(
 168         &mut self,
 169         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 170     ) {
 171         self.late_module_passes.push(Box::new(pass));
 172     }
 173
 174     // Helper method for register_early/late_pass
 175     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 176         for lint in lints {
 177             self.lints.push(lint);
 178
 179             let id = LintId::of(lint);
 180             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 181                 bug!("duplicate specification of lint {}", lint.name_lower())
 182             }
 183
 184             if let Some(FutureIncompatibleInfo { edition, .. }) = lint.future_incompatible {
 185                 if let Some(edition) = edition {
 186                     self.lint_groups
 187                         .entry(edition.lint_name())
 188                         .or_insert(LintGroup {
 189                             lint_ids: vec![],
 190                             from_plugin: lint.is_plugin,
 191                             depr: None,
 192                         })
 193                         .lint_ids
 194                         .push(id);
 195                 }
 196
 197                 self.lint_groups
 198                     .entry("future_incompatible")
 199                     .or_insert(LintGroup {
 200                         lint_ids: vec![],
 201                         from_plugin: lint.is_plugin,
 202                         depr: None,
 203                     })
 204                     .lint_ids
 205                     .push(id);
 206             }
 207         }
 208     }
 209
 210     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 211         self.lint_groups.insert(
 212             alias,
 213             LintGroup {
 214                 lint_ids: vec![],
 215                 from_plugin: false,
 216                 depr: Some(LintAlias { name: lint_name, silent: true }),
 217             },
 218         );
 219     }
 220
 221     pub fn register_group(
 222         &mut self,
 223         from_plugin: bool,
 224         name: &'static str,
 225         deprecated_name: Option<&'static str>,
 226         to: Vec<LintId>,
 227     ) {
 228         let new = self
 229             .lint_groups
 230             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 231             .is_none();
 232         if let Some(deprecated) = deprecated_name {
 233             self.lint_groups.insert(
 234                 deprecated,
 235                 LintGroup {
 236                     lint_ids: vec![],
 237                     from_plugin,
 238                     depr: Some(LintAlias { name, silent: false }),
 239                 },
 240             );
 241         }
 242
 243         if !new {
 244             bug!("duplicate specification of lint group {}", name);
 245         }
 246     }
 247
 248     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 249         let target = match self.by_name.get(new_name) {
 250             Some(&Id(lint_id)) => lint_id,
 251             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 252         };
 253         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 254     }
 255
 256     pub fn register_removed(&mut self, name: &str, reason: &str) {
 257         self.by_name.insert(name.into(), Removed(reason.into()));
 258     }
 259
 260     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 261         match self.by_name.get(lint_name) {
 262             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 263             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 264             Some(&Removed(_)) => Err(FindLintError::Removed),
 265             None => loop {
 266                 return match self.lint_groups.get(lint_name) {
 267                     Some(LintGroup { lint_ids, depr, .. }) => {
 268                         if let Some(LintAlias { name, .. }) = depr {
 269                             lint_name = name;
 270                             continue;
 271                         }
 272                         Ok(lint_ids.clone())
 273                     }
 274                     None => Err(FindLintError::Removed),
 275                 };
 276             },
 277         }
 278     }
 279
 280     /// Checks the validity of lint names derived from the command line
 281     pub fn check_lint_name_cmdline(&self, sess: &Session, lint_name: &str, level: Level) {
 282         let db = match self.check_lint_name(lint_name, None) {
 283             CheckLintNameResult::Ok(_) => None,
 284             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 285             CheckLintNameResult::NoLint(suggestion) => {
 286                 let mut err =
 287                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 288
 289                 if let Some(suggestion) = suggestion {
 290                     err.help(&format!("did you mean: `{}`", suggestion));
 291                 }
 292
 293                 Some(err)
 294             }
 295             CheckLintNameResult::Tool(result) => match result {
 296                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 297                     "lint name `{}` is deprecated \
 298                      and does not have an effect anymore. \
 299                      Use: {}",
 300                     lint_name, new_name
 301                 ))),
 302                 _ => None,
 303             },
 304         };
 305
 306         if let Some(mut db) = db {
 307             let msg = format!(
 308                 "requested on the command line with `{} {}`",
 309                 match level {
 310                     Level::Allow => "-A",
 311                     Level::Warn => "-W",
 312                     Level::Deny => "-D",
 313                     Level::Forbid => "-F",
 314                 },
 315                 lint_name
 316             );
 317             db.note(&msg);
 318             db.emit();
 319         }
 320     }
 321
 322     /// Checks the name of a lint for its existence, and whether it was
 323     /// renamed or removed. Generates a DiagnosticBuilder containing a
 324     /// warning for renamed and removed lints. This is over both lint
 325     /// names from attributes and those passed on the command line. Since
 326     /// it emits non-fatal warnings and there are *two* lint passes that
 327     /// inspect attributes, this is only run from the late pass to avoid
 328     /// printing duplicate warnings.
 329     pub fn check_lint_name(
 330         &self,
 331         lint_name: &str,
 332         tool_name: Option<Symbol>,
 333     ) -> CheckLintNameResult<'_> {
 334         let complete_name = if let Some(tool_name) = tool_name {
 335             format!("{}::{}", tool_name, lint_name)
 336         } else {
 337             lint_name.to_string()
 338         };
 339         // If the lint was scoped with `tool::` check if the tool lint exists
 340         if tool_name.is_some() {
 341             match self.by_name.get(&complete_name) {
 342                 None => match self.lint_groups.get(&*complete_name) {
 343                     None => return CheckLintNameResult::Tool(Err((None, String::new()))),
 344                     Some(LintGroup { lint_ids, .. }) => {
 345                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 346                     }
 347                 },
 348                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 349                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 350                 // to treat tool_lints and rustc lints different and can use the code below.
 351                 _ => {}
 352             }
 353         }
 354         match self.by_name.get(&complete_name) {
 355             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 356                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 357                 Some(new_name.to_owned()),
 358             ),
 359             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 360                 format!("lint `{}` has been removed: `{}`", complete_name, reason),
 361                 None,
 362             ),
 363             None => match self.lint_groups.get(&*complete_name) {
 364                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 365                 // variant of this lint
 366                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 367                 Some(LintGroup { lint_ids, depr, .. }) => {
 368                     // Check if the lint group name is deprecated
 369                     if let Some(LintAlias { name, silent }) = depr {
 370                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 371                         return if *silent {
 372                             CheckLintNameResult::Ok(&lint_ids)
 373                         } else {
 374                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 375                         };
 376                     }
 377                     CheckLintNameResult::Ok(&lint_ids)
 378                 }
 379             },
 380             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 381         }
 382     }
 383
 384     fn check_tool_name_for_backwards_compat(
 385         &self,
 386         lint_name: &str,
 387         tool_name: &str,
 388     ) -> CheckLintNameResult<'_> {
 389         let complete_name = format!("{}::{}", tool_name, lint_name);
 390         match self.by_name.get(&complete_name) {
 391             None => match self.lint_groups.get(&*complete_name) {
 392                 // Now we are sure, that this lint exists nowhere
 393                 None => {
 394                     let symbols =
 395                         self.by_name.keys().map(|name| Symbol::intern(&name)).collect::<Vec<_>>();
 396
 397                     let suggestion = find_best_match_for_name(
 398                         symbols.iter(),
 399                         Symbol::intern(&lint_name.to_lowercase()),
 400                         None,
 401                     );
 402
 403                     CheckLintNameResult::NoLint(suggestion)
 404                 }
 405                 Some(LintGroup { lint_ids, depr, .. }) => {
 406                     // Reaching this would be weird, but let's cover this case anyway
 407                     if let Some(LintAlias { name, silent }) = depr {
 408                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 409                         return if *silent {
 410                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 411                         } else {
 412                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 413                         };
 414                     }
 415                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 416                 }
 417             },
 418             Some(&Id(ref id)) => {
 419                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 420             }
 421             _ => CheckLintNameResult::NoLint(None),
 422         }
 423     }
 424 }
 425
 426 /// Context for lint checking after type checking.
 427 pub struct LateContext<'tcx> {
 428     /// Type context we're checking in.
 429     pub tcx: TyCtxt<'tcx>,
 430
 431     /// Current body, or `None` if outside a body.
 432     pub enclosing_body: Option<hir::BodyId>,
 433
 434     /// Type-checking results for the current body. Access using the `typeck_results`
 435     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 436     // FIXME(eddyb) move all the code accessing internal fields like this,
 437     // to this module, to avoid exposing it to lint logic.
 438     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 439
 440     /// Parameter environment for the item we are in.
 441     pub param_env: ty::ParamEnv<'tcx>,
 442
 443     /// Items accessible from the crate being checked.
 444     pub access_levels: &'tcx AccessLevels,
 445
 446     /// The store of registered lints and the lint levels.
 447     pub lint_store: &'tcx LintStore,
 448
 449     pub last_node_with_lint_attrs: hir::HirId,
 450
 451     /// Generic type parameters in scope for the item we are in.
 452     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 453
 454     /// We are only looking at one module
 455     pub only_module: bool,
 456 }
 457
 458 /// Context for lint checking of the AST, after expansion, before lowering to
 459 /// HIR.
 460 pub struct EarlyContext<'a> {
 461     /// Type context we're checking in.
 462     pub sess: &'a Session,
 463
 464     /// The crate being checked.
 465     pub krate: &'a ast::Crate,
 466
 467     pub builder: LintLevelsBuilder<'a>,
 468
 469     /// The store of registered lints and the lint levels.
 470     pub lint_store: &'a LintStore,
 471
 472     pub buffered: LintBuffer,
 473 }
 474
 475 pub trait LintPassObject: Sized {}
 476
 477 impl LintPassObject for EarlyLintPassObject {}
 478
 479 impl LintPassObject for LateLintPassObject {}
 480
 481 pub trait LintContext: Sized {
 482     type PassObject: LintPassObject;
 483
 484     fn sess(&self) -> &Session;
 485     fn lints(&self) -> &LintStore;
 486
 487     fn lookup_with_diagnostics(
 488         &self,
 489         lint: &'static Lint,
 490         span: Option<impl Into<MultiSpan>>,
 491         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 492         diagnostic: BuiltinLintDiagnostics,
 493     ) {
 494         self.lookup(lint, span, |lint| {
 495             // We first generate a blank diagnostic.
 496             let mut db = lint.build("");
 497
 498             // Now, set up surrounding context.
 499             let sess = self.sess();
 500             match diagnostic {
 501                 BuiltinLintDiagnostics::Normal => (),
 502                 BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 503                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 504                         Ok(s) if is_global => {
 505                             (format!("dyn ({})", s), Applicability::MachineApplicable)
 506                         }
 507                         Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 508                         Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
 509                     };
 510                     db.span_suggestion(span, "use `dyn`", sugg, app);
 511                 }
 512                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 513                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 514                         Ok(ref s) => {
 515                             // FIXME(Manishearth) ideally the emitting code
 516                             // can tell us whether or not this is global
 517                             let opt_colon =
 518                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 519
 520                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 521                         }
 522                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 523                     };
 524                     db.span_suggestion(span, "use `crate`", sugg, app);
 525                 }
 526                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 527                     db.span_label(
 528                         span,
 529                         "names from parent modules are not accessible without an explicit import",
 530                     );
 531                 }
 532                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 533                     span_def,
 534                 ) => {
 535                     db.span_note(span_def, "the macro is defined here");
 536                 }
 537                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 538                     n,
 539                     path_span,
 540                     incl_angl_brckt,
 541                     insertion_span,
 542                     anon_lts,
 543                 ) => {
 544                     add_elided_lifetime_in_path_suggestion(
 545                         sess,
 546                         &mut db,
 547                         n,
 548                         path_span,
 549                         incl_angl_brckt,
 550                         insertion_span,
 551                         anon_lts,
 552                     );
 553                 }
 554                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 555                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 556                 }
 557                 BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
 558                     if !replaces.is_empty() {
 559                         db.tool_only_multipart_suggestion(
 560                             &message,
 561                             replaces,
 562                             Applicability::MachineApplicable,
 563                         );
 564                     }
 565                 }
 566                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 567                     for (span, is_imported) in spans {
 568                         let introduced = if is_imported { "imported" } else { "defined" };
 569                         db.span_label(
 570                             span,
 571                             format!("the item `{}` is already {} here", ident, introduced),
 572                         );
 573                     }
 574                 }
 575                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 576                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 577                 }
 578                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 579                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 580                     db.help("to document an item produced by a macro, \
 581                                   the macro must produce the documentation as part of its expansion");
 582                 }
 583             }
 584             // Rewrap `db`, and pass control to the user.
 585             decorate(LintDiagnosticBuilder::new(db));
 586         });
 587     }
 588
 589     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 590     // set the span in their `decorate` function (preferably using set_span).
 591     fn lookup<S: Into<MultiSpan>>(
 592         &self,
 593         lint: &'static Lint,
 594         span: Option<S>,
 595         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 596     );
 597
 598     fn struct_span_lint<S: Into<MultiSpan>>(
 599         &self,
 600         lint: &'static Lint,
 601         span: S,
 602         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 603     ) {
 604         self.lookup(lint, Some(span), decorate);
 605     }
 606     /// Emit a lint at the appropriate level, with no associated span.
 607     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 608         self.lookup(lint, None as Option<Span>, decorate);
 609     }
 610 }
 611
 612 impl<'a> EarlyContext<'a> {
 613     pub fn new(
 614         sess: &'a Session,
 615         lint_store: &'a LintStore,
 616         krate: &'a ast::Crate,
 617         buffered: LintBuffer,
 618         warn_about_weird_lints: bool,
 619     ) -> EarlyContext<'a> {
 620         EarlyContext {
 621             sess,
 622             krate,
 623             lint_store,
 624             builder: LintLevelsBuilder::new(sess, warn_about_weird_lints, lint_store),
 625             buffered,
 626         }
 627     }
 628 }
 629
 630 impl LintContext for LateContext<'_> {
 631     type PassObject = LateLintPassObject;
 632
 633     /// Gets the overall compiler `Session` object.
 634     fn sess(&self) -> &Session {
 635         &self.tcx.sess
 636     }
 637
 638     fn lints(&self) -> &LintStore {
 639         &*self.lint_store
 640     }
 641
 642     fn lookup<S: Into<MultiSpan>>(
 643         &self,
 644         lint: &'static Lint,
 645         span: Option<S>,
 646         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 647     ) {
 648         let hir_id = self.last_node_with_lint_attrs;
 649
 650         match span {
 651             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 652             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 653         }
 654     }
 655 }
 656
 657 impl LintContext for EarlyContext<'_> {
 658     type PassObject = EarlyLintPassObject;
 659
 660     /// Gets the overall compiler `Session` object.
 661     fn sess(&self) -> &Session {
 662         &self.sess
 663     }
 664
 665     fn lints(&self) -> &LintStore {
 666         &*self.lint_store
 667     }
 668
 669     fn lookup<S: Into<MultiSpan>>(
 670         &self,
 671         lint: &'static Lint,
 672         span: Option<S>,
 673         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 674     ) {
 675         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 676     }
 677 }
 678
 679 impl<'tcx> LateContext<'tcx> {
 680     /// Gets the type-checking results for the current body,
 681     /// or `None` if outside a body.
 682     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 683         self.cached_typeck_results.get().or_else(|| {
 684             self.enclosing_body.map(|body| {
 685                 let typeck_results = self.tcx.typeck_body(body);
 686                 self.cached_typeck_results.set(Some(typeck_results));
 687                 typeck_results
 688             })
 689         })
 690     }
 691
 692     /// Gets the type-checking results for the current body.
 693     /// As this will ICE if called outside bodies, only call when working with
 694     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 695     #[track_caller]
 696     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 697         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 698     }
 699
 700     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 701     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 702     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 703     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 704         match *qpath {
 705             hir::QPath::Resolved(_, ref path) => path.res,
 706             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 707                 .maybe_typeck_results()
 708                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 709                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 710         }
 711     }
 712
 713     pub fn current_lint_root(&self) -> hir::HirId {
 714         self.last_node_with_lint_attrs
 715     }
 716
 717     /// Check if a `DefId`'s path matches the given absolute type path usage.
 718     ///
 719     /// Anonymous scopes such as `extern` imports are matched with `kw::Invalid`;
 720     /// inherent `impl` blocks are matched with the name of the type.
 721     ///
 722     /// # Examples
 723     ///
 724     /// ```rust,ignore (no context or def id available)
 725     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 726     ///     // The given `def_id` is that of an `Option` type
 727     /// }
 728     /// ```
 729     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 730         let names = self.get_def_path(def_id);
 731
 732         names.len() == path.len() && names.into_iter().zip(path.iter()).all(|(a, &b)| a == b)
 733     }
 734
 735     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 736     ///
 737     /// # Examples
 738     ///
 739     /// ```rust,ignore (no context or def id available)
 740     /// let def_path = cx.get_def_path(def_id);
 741     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 742     ///     // The given `def_id` is that of an `Option` type
 743     /// }
 744     /// ```
 745     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 746         pub struct AbsolutePathPrinter<'tcx> {
 747             pub tcx: TyCtxt<'tcx>,
 748         }
 749
 750         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 751             type Error = !;
 752
 753             type Path = Vec<Symbol>;
 754             type Region = ();
 755             type Type = ();
 756             type DynExistential = ();
 757             type Const = ();
 758
 759             fn tcx(&self) -> TyCtxt<'tcx> {
 760                 self.tcx
 761             }
 762
 763             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 764                 Ok(())
 765             }
 766
 767             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 768                 Ok(())
 769             }
 770
 771             fn print_dyn_existential(
 772                 self,
 773                 _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 774             ) -> Result<Self::DynExistential, Self::Error> {
 775                 Ok(())
 776             }
 777
 778             fn print_const(self, _ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 779                 Ok(())
 780             }
 781
 782             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 783                 Ok(vec![self.tcx.original_crate_name(cnum)])
 784             }
 785
 786             fn path_qualified(
 787                 self,
 788                 self_ty: Ty<'tcx>,
 789                 trait_ref: Option<ty::TraitRef<'tcx>>,
 790             ) -> Result<Self::Path, Self::Error> {
 791                 if trait_ref.is_none() {
 792                     if let ty::Adt(def, substs) = self_ty.kind {
 793                         return self.print_def_path(def.did, substs);
 794                     }
 795                 }
 796
 797                 // This shouldn't ever be needed, but just in case:
 798                 Ok(vec![match trait_ref {
 799                     Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
 800                     None => Symbol::intern(&format!("<{}>", self_ty)),
 801                 }])
 802             }
 803
 804             fn path_append_impl(
 805                 self,
 806                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 807                 _disambiguated_data: &DisambiguatedDefPathData,
 808                 self_ty: Ty<'tcx>,
 809                 trait_ref: Option<ty::TraitRef<'tcx>>,
 810             ) -> Result<Self::Path, Self::Error> {
 811                 let mut path = print_prefix(self)?;
 812
 813                 // This shouldn't ever be needed, but just in case:
 814                 path.push(match trait_ref {
 815                     Some(trait_ref) => Symbol::intern(&format!(
 816                         "<impl {} for {}>",
 817                         trait_ref.print_only_trait_path(),
 818                         self_ty
 819                     )),
 820                     None => Symbol::intern(&format!("<impl {}>", self_ty)),
 821                 });
 822
 823                 Ok(path)
 824             }
 825
 826             fn path_append(
 827                 self,
 828                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 829                 disambiguated_data: &DisambiguatedDefPathData,
 830             ) -> Result<Self::Path, Self::Error> {
 831                 let mut path = print_prefix(self)?;
 832
 833                 // Skip `::{{constructor}}` on tuple/unit structs.
 834                 if let DefPathData::Ctor = disambiguated_data.data {
 835                     return Ok(path);
 836                 }
 837
 838                 path.push(disambiguated_data.data.as_symbol());
 839                 Ok(path)
 840             }
 841
 842             fn path_generic_args(
 843                 self,
 844                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 845                 _args: &[GenericArg<'tcx>],
 846             ) -> Result<Self::Path, Self::Error> {
 847                 print_prefix(self)
 848             }
 849         }
 850
 851         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
 852     }
 853 }
 854
 855 impl<'tcx> LayoutOf for LateContext<'tcx> {
 856     type Ty = Ty<'tcx>;
 857     type TyAndLayout = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 858
 859     fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyAndLayout {
 860         self.tcx.layout_of(self.param_env.and(ty))
 861     }
 862 }