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_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::print::with_no_trimmed_paths;
  35 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, Ty, TyCtxt};
  36 use rustc_session::lint::{add_elided_lifetime_in_path_suggestion, BuiltinLintDiagnostics};
  37 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  38 use rustc_session::Session;
  39 use rustc_span::{symbol::Symbol, MultiSpan, Span, DUMMY_SP};
  40 use rustc_target::abi::LayoutOf;
  41
  42 use std::cell::Cell;
  43 use std::slice;
  44
  45 /// Information about the registered lints.
  46 ///
  47 /// This is basically the subset of `Context` that we can
  48 /// build early in the compile pipeline.
  49 pub struct LintStore {
  50     /// Registered lints.
  51     lints: Vec<&'static Lint>,
  52
  53     /// Constructor functions for each variety of lint pass.
  54     ///
  55     /// These should only be called once, but since we want to avoid locks or
  56     /// interior mutability, we don't enforce this (and lints should, in theory,
  57     /// be compatible with being constructed more than once, though not
  58     /// necessarily in a sane manner. This is safe though.)
  59     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  60     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  61     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  62     /// This is unique in that we construct them per-module, so not once.
  63     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  64
  65     /// Lints indexed by name.
  66     by_name: FxHashMap<String, TargetLint>,
  67
  68     /// Map of registered lint groups to what lints they expand to.
  69     lint_groups: FxHashMap<&'static str, LintGroup>,
  70 }
  71
  72 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  73 enum TargetLint {
  74     /// A direct lint target
  75     Id(LintId),
  76
  77     /// Temporary renaming, used for easing migration pain; see #16545
  78     Renamed(String, LintId),
  79
  80     /// Lint with this name existed previously, but has been removed/deprecated.
  81     /// The string argument is the reason for removal.
  82     Removed(String),
  83 }
  84
  85 pub enum FindLintError {
  86     NotFound,
  87     Removed,
  88 }
  89
  90 struct LintAlias {
  91     name: &'static str,
  92     /// Whether deprecation warnings should be suppressed for this alias.
  93     silent: bool,
  94 }
  95
  96 struct LintGroup {
  97     lint_ids: Vec<LintId>,
  98     from_plugin: bool,
  99     depr: Option<LintAlias>,
 100 }
 101
 102 pub enum CheckLintNameResult<'a> {
 103     Ok(&'a [LintId]),
 104     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 105     NoLint(Option<Symbol>),
 106     /// The lint is either renamed or removed. This is the warning
 107     /// message, and an optional new name (`None` if removed).
 108     Warning(String, Option<String>),
 109     /// The lint is from a tool. If the Option is None, then either
 110     /// the lint does not exist in the tool or the code was not
 111     /// compiled with the tool and therefore the lint was never
 112     /// added to the `LintStore`. Otherwise the `LintId` will be
 113     /// returned as if it where a rustc lint.
 114     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 115 }
 116
 117 impl LintStore {
 118     pub fn new() -> LintStore {
 119         LintStore {
 120             lints: vec![],
 121             pre_expansion_passes: vec![],
 122             early_passes: vec![],
 123             late_passes: vec![],
 124             late_module_passes: vec![],
 125             by_name: Default::default(),
 126             lint_groups: Default::default(),
 127         }
 128     }
 129
 130     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 131         &self.lints
 132     }
 133
 134     pub fn get_lint_groups<'t>(&'t self) -> Vec<(&'static str, Vec<LintId>, bool)> {
 135         self.lint_groups
 136             .iter()
 137             .filter(|(_, LintGroup { depr, .. })| {
 138                 // Don't display deprecated lint groups.
 139                 depr.is_none()
 140             })
 141             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 142                 (*k, lint_ids.clone(), *from_plugin)
 143             })
 144             .collect()
 145     }
 146
 147     pub fn register_early_pass(
 148         &mut self,
 149         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 150     ) {
 151         self.early_passes.push(Box::new(pass));
 152     }
 153
 154     pub fn register_pre_expansion_pass(
 155         &mut self,
 156         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 157     ) {
 158         self.pre_expansion_passes.push(Box::new(pass));
 159     }
 160
 161     pub fn register_late_pass(
 162         &mut self,
 163         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 164     ) {
 165         self.late_passes.push(Box::new(pass));
 166     }
 167
 168     pub fn register_late_mod_pass(
 169         &mut self,
 170         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 171     ) {
 172         self.late_module_passes.push(Box::new(pass));
 173     }
 174
 175     // Helper method for register_early/late_pass
 176     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 177         for lint in lints {
 178             self.lints.push(lint);
 179
 180             let id = LintId::of(lint);
 181             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 182                 bug!("duplicate specification of lint {}", lint.name_lower())
 183             }
 184
 185             if let Some(FutureIncompatibleInfo { edition, .. }) = lint.future_incompatible {
 186                 if let Some(edition) = edition {
 187                     self.lint_groups
 188                         .entry(edition.lint_name())
 189                         .or_insert(LintGroup {
 190                             lint_ids: vec![],
 191                             from_plugin: lint.is_plugin,
 192                             depr: None,
 193                         })
 194                         .lint_ids
 195                         .push(id);
 196                 }
 197
 198                 self.lint_groups
 199                     .entry("future_incompatible")
 200                     .or_insert(LintGroup {
 201                         lint_ids: vec![],
 202                         from_plugin: lint.is_plugin,
 203                         depr: None,
 204                     })
 205                     .lint_ids
 206                     .push(id);
 207             }
 208         }
 209     }
 210
 211     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 212         self.lint_groups.insert(
 213             alias,
 214             LintGroup {
 215                 lint_ids: vec![],
 216                 from_plugin: false,
 217                 depr: Some(LintAlias { name: lint_name, silent: true }),
 218             },
 219         );
 220     }
 221
 222     pub fn register_group(
 223         &mut self,
 224         from_plugin: bool,
 225         name: &'static str,
 226         deprecated_name: Option<&'static str>,
 227         to: Vec<LintId>,
 228     ) {
 229         let new = self
 230             .lint_groups
 231             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 232             .is_none();
 233         if let Some(deprecated) = deprecated_name {
 234             self.lint_groups.insert(
 235                 deprecated,
 236                 LintGroup {
 237                     lint_ids: vec![],
 238                     from_plugin,
 239                     depr: Some(LintAlias { name, silent: false }),
 240                 },
 241             );
 242         }
 243
 244         if !new {
 245             bug!("duplicate specification of lint group {}", name);
 246         }
 247     }
 248
 249     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 250         let target = match self.by_name.get(new_name) {
 251             Some(&Id(lint_id)) => lint_id,
 252             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 253         };
 254         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 255     }
 256
 257     pub fn register_removed(&mut self, name: &str, reason: &str) {
 258         self.by_name.insert(name.into(), Removed(reason.into()));
 259     }
 260
 261     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 262         match self.by_name.get(lint_name) {
 263             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 264             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 265             Some(&Removed(_)) => Err(FindLintError::Removed),
 266             None => loop {
 267                 return match self.lint_groups.get(lint_name) {
 268                     Some(LintGroup { lint_ids, depr, .. }) => {
 269                         if let Some(LintAlias { name, .. }) = depr {
 270                             lint_name = name;
 271                             continue;
 272                         }
 273                         Ok(lint_ids.clone())
 274                     }
 275                     None => Err(FindLintError::Removed),
 276                 };
 277             },
 278         }
 279     }
 280
 281     /// Checks the validity of lint names derived from the command line
 282     pub fn check_lint_name_cmdline(&self, sess: &Session, lint_name: &str, level: Level) {
 283         let db = match self.check_lint_name(lint_name, None) {
 284             CheckLintNameResult::Ok(_) => None,
 285             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 286             CheckLintNameResult::NoLint(suggestion) => {
 287                 let mut err =
 288                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 289
 290                 if let Some(suggestion) = suggestion {
 291                     err.help(&format!("did you mean: `{}`", suggestion));
 292                 }
 293
 294                 Some(err)
 295             }
 296             CheckLintNameResult::Tool(result) => match result {
 297                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 298                     "lint name `{}` is deprecated \
 299                      and does not have an effect anymore. \
 300                      Use: {}",
 301                     lint_name, new_name
 302                 ))),
 303                 _ => None,
 304             },
 305         };
 306
 307         if let Some(mut db) = db {
 308             let msg = format!(
 309                 "requested on the command line with `{} {}`",
 310                 match level {
 311                     Level::Allow => "-A",
 312                     Level::Warn => "-W",
 313                     Level::Deny => "-D",
 314                     Level::Forbid => "-F",
 315                 },
 316                 lint_name
 317             );
 318             db.note(&msg);
 319             db.emit();
 320         }
 321     }
 322
 323     /// Checks the name of a lint for its existence, and whether it was
 324     /// renamed or removed. Generates a DiagnosticBuilder containing a
 325     /// warning for renamed and removed lints. This is over both lint
 326     /// names from attributes and those passed on the command line. Since
 327     /// it emits non-fatal warnings and there are *two* lint passes that
 328     /// inspect attributes, this is only run from the late pass to avoid
 329     /// printing duplicate warnings.
 330     pub fn check_lint_name(
 331         &self,
 332         lint_name: &str,
 333         tool_name: Option<Symbol>,
 334     ) -> CheckLintNameResult<'_> {
 335         let complete_name = if let Some(tool_name) = tool_name {
 336             format!("{}::{}", tool_name, lint_name)
 337         } else {
 338             lint_name.to_string()
 339         };
 340         // If the lint was scoped with `tool::` check if the tool lint exists
 341         if tool_name.is_some() {
 342             match self.by_name.get(&complete_name) {
 343                 None => match self.lint_groups.get(&*complete_name) {
 344                     None => return CheckLintNameResult::Tool(Err((None, String::new()))),
 345                     Some(LintGroup { lint_ids, .. }) => {
 346                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 347                     }
 348                 },
 349                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 350                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 351                 // to treat tool_lints and rustc lints different and can use the code below.
 352                 _ => {}
 353             }
 354         }
 355         match self.by_name.get(&complete_name) {
 356             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 357                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 358                 Some(new_name.to_owned()),
 359             ),
 360             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 361                 format!("lint `{}` has been removed: `{}`", complete_name, reason),
 362                 None,
 363             ),
 364             None => match self.lint_groups.get(&*complete_name) {
 365                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 366                 // variant of this lint
 367                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 368                 Some(LintGroup { lint_ids, depr, .. }) => {
 369                     // Check if the lint group name is deprecated
 370                     if let Some(LintAlias { name, silent }) = depr {
 371                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 372                         return if *silent {
 373                             CheckLintNameResult::Ok(&lint_ids)
 374                         } else {
 375                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 376                         };
 377                     }
 378                     CheckLintNameResult::Ok(&lint_ids)
 379                 }
 380             },
 381             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 382         }
 383     }
 384
 385     fn check_tool_name_for_backwards_compat(
 386         &self,
 387         lint_name: &str,
 388         tool_name: &str,
 389     ) -> CheckLintNameResult<'_> {
 390         let complete_name = format!("{}::{}", tool_name, lint_name);
 391         match self.by_name.get(&complete_name) {
 392             None => match self.lint_groups.get(&*complete_name) {
 393                 // Now we are sure, that this lint exists nowhere
 394                 None => {
 395                     let symbols =
 396                         self.by_name.keys().map(|name| Symbol::intern(&name)).collect::<Vec<_>>();
 397
 398                     let suggestion = find_best_match_for_name(
 399                         symbols.iter(),
 400                         Symbol::intern(&lint_name.to_lowercase()),
 401                         None,
 402                     );
 403
 404                     CheckLintNameResult::NoLint(suggestion)
 405                 }
 406                 Some(LintGroup { lint_ids, depr, .. }) => {
 407                     // Reaching this would be weird, but let's cover this case anyway
 408                     if let Some(LintAlias { name, silent }) = depr {
 409                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 410                         return if *silent {
 411                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 412                         } else {
 413                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 414                         };
 415                     }
 416                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 417                 }
 418             },
 419             Some(&Id(ref id)) => {
 420                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 421             }
 422             _ => CheckLintNameResult::NoLint(None),
 423         }
 424     }
 425 }
 426
 427 /// Context for lint checking after type checking.
 428 pub struct LateContext<'tcx> {
 429     /// Type context we're checking in.
 430     pub tcx: TyCtxt<'tcx>,
 431
 432     /// Current body, or `None` if outside a body.
 433     pub enclosing_body: Option<hir::BodyId>,
 434
 435     /// Type-checking results for the current body. Access using the `typeck_results`
 436     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 437     // FIXME(eddyb) move all the code accessing internal fields like this,
 438     // to this module, to avoid exposing it to lint logic.
 439     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 440
 441     /// Parameter environment for the item we are in.
 442     pub param_env: ty::ParamEnv<'tcx>,
 443
 444     /// Items accessible from the crate being checked.
 445     pub access_levels: &'tcx AccessLevels,
 446
 447     /// The store of registered lints and the lint levels.
 448     pub lint_store: &'tcx LintStore,
 449
 450     pub last_node_with_lint_attrs: hir::HirId,
 451
 452     /// Generic type parameters in scope for the item we are in.
 453     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 454
 455     /// We are only looking at one module
 456     pub only_module: bool,
 457 }
 458
 459 /// Context for lint checking of the AST, after expansion, before lowering to
 460 /// HIR.
 461 pub struct EarlyContext<'a> {
 462     /// Type context we're checking in.
 463     pub sess: &'a Session,
 464
 465     /// The crate being checked.
 466     pub krate: &'a ast::Crate,
 467
 468     pub builder: LintLevelsBuilder<'a>,
 469
 470     /// The store of registered lints and the lint levels.
 471     pub lint_store: &'a LintStore,
 472
 473     pub buffered: LintBuffer,
 474 }
 475
 476 pub trait LintPassObject: Sized {}
 477
 478 impl LintPassObject for EarlyLintPassObject {}
 479
 480 impl LintPassObject for LateLintPassObject {}
 481
 482 pub trait LintContext: Sized {
 483     type PassObject: LintPassObject;
 484
 485     fn sess(&self) -> &Session;
 486     fn lints(&self) -> &LintStore;
 487
 488     fn lookup_with_diagnostics(
 489         &self,
 490         lint: &'static Lint,
 491         span: Option<impl Into<MultiSpan>>,
 492         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 493         diagnostic: BuiltinLintDiagnostics,
 494     ) {
 495         self.lookup(lint, span, |lint| {
 496             // We first generate a blank diagnostic.
 497             let mut db = lint.build("");
 498
 499             // Now, set up surrounding context.
 500             let sess = self.sess();
 501             match diagnostic {
 502                 BuiltinLintDiagnostics::Normal => (),
 503                 BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 504                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 505                         Ok(s) if is_global => {
 506                             (format!("dyn ({})", s), Applicability::MachineApplicable)
 507                         }
 508                         Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 509                         Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
 510                     };
 511                     db.span_suggestion(span, "use `dyn`", sugg, app);
 512                 }
 513                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 514                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 515                         Ok(ref s) => {
 516                             // FIXME(Manishearth) ideally the emitting code
 517                             // can tell us whether or not this is global
 518                             let opt_colon =
 519                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 520
 521                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 522                         }
 523                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 524                     };
 525                     db.span_suggestion(span, "use `crate`", sugg, app);
 526                 }
 527                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 528                     db.span_label(
 529                         span,
 530                         "names from parent modules are not accessible without an explicit import",
 531                     );
 532                 }
 533                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 534                     span_def,
 535                 ) => {
 536                     db.span_note(span_def, "the macro is defined here");
 537                 }
 538                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 539                     n,
 540                     path_span,
 541                     incl_angl_brckt,
 542                     insertion_span,
 543                     anon_lts,
 544                 ) => {
 545                     add_elided_lifetime_in_path_suggestion(
 546                         sess,
 547                         &mut db,
 548                         n,
 549                         path_span,
 550                         incl_angl_brckt,
 551                         insertion_span,
 552                         anon_lts,
 553                     );
 554                 }
 555                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 556                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 557                 }
 558                 BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
 559                     if !replaces.is_empty() {
 560                         db.tool_only_multipart_suggestion(
 561                             &message,
 562                             replaces,
 563                             Applicability::MachineApplicable,
 564                         );
 565                     }
 566                 }
 567                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 568                     for (span, is_imported) in spans {
 569                         let introduced = if is_imported { "imported" } else { "defined" };
 570                         db.span_label(
 571                             span,
 572                             format!("the item `{}` is already {} here", ident, introduced),
 573                         );
 574                     }
 575                 }
 576                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 577                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 578                 }
 579                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 580                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 581                     db.help("to document an item produced by a macro, \
 582                                   the macro must produce the documentation as part of its expansion");
 583                 }
 584             }
 585             // Rewrap `db`, and pass control to the user.
 586             decorate(LintDiagnosticBuilder::new(db));
 587         });
 588     }
 589
 590     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 591     // set the span in their `decorate` function (preferably using set_span).
 592     fn lookup<S: Into<MultiSpan>>(
 593         &self,
 594         lint: &'static Lint,
 595         span: Option<S>,
 596         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 597     );
 598
 599     fn struct_span_lint<S: Into<MultiSpan>>(
 600         &self,
 601         lint: &'static Lint,
 602         span: S,
 603         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 604     ) {
 605         self.lookup(lint, Some(span), decorate);
 606     }
 607     /// Emit a lint at the appropriate level, with no associated span.
 608     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 609         self.lookup(lint, None as Option<Span>, decorate);
 610     }
 611 }
 612
 613 impl<'a> EarlyContext<'a> {
 614     pub fn new(
 615         sess: &'a Session,
 616         lint_store: &'a LintStore,
 617         krate: &'a ast::Crate,
 618         buffered: LintBuffer,
 619         warn_about_weird_lints: bool,
 620     ) -> EarlyContext<'a> {
 621         EarlyContext {
 622             sess,
 623             krate,
 624             lint_store,
 625             builder: LintLevelsBuilder::new(sess, warn_about_weird_lints, lint_store),
 626             buffered,
 627         }
 628     }
 629 }
 630
 631 impl LintContext for LateContext<'_> {
 632     type PassObject = LateLintPassObject;
 633
 634     /// Gets the overall compiler `Session` object.
 635     fn sess(&self) -> &Session {
 636         &self.tcx.sess
 637     }
 638
 639     fn lints(&self) -> &LintStore {
 640         &*self.lint_store
 641     }
 642
 643     fn lookup<S: Into<MultiSpan>>(
 644         &self,
 645         lint: &'static Lint,
 646         span: Option<S>,
 647         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 648     ) {
 649         let hir_id = self.last_node_with_lint_attrs;
 650
 651         match span {
 652             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 653             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 654         }
 655     }
 656 }
 657
 658 impl LintContext for EarlyContext<'_> {
 659     type PassObject = EarlyLintPassObject;
 660
 661     /// Gets the overall compiler `Session` object.
 662     fn sess(&self) -> &Session {
 663         &self.sess
 664     }
 665
 666     fn lints(&self) -> &LintStore {
 667         &*self.lint_store
 668     }
 669
 670     fn lookup<S: Into<MultiSpan>>(
 671         &self,
 672         lint: &'static Lint,
 673         span: Option<S>,
 674         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 675     ) {
 676         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 677     }
 678 }
 679
 680 impl<'tcx> LateContext<'tcx> {
 681     /// Gets the type-checking results for the current body,
 682     /// or `None` if outside a body.
 683     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 684         self.cached_typeck_results.get().or_else(|| {
 685             self.enclosing_body.map(|body| {
 686                 let typeck_results = self.tcx.typeck_body(body);
 687                 self.cached_typeck_results.set(Some(typeck_results));
 688                 typeck_results
 689             })
 690         })
 691     }
 692
 693     /// Gets the type-checking results for the current body.
 694     /// As this will ICE if called outside bodies, only call when working with
 695     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 696     #[track_caller]
 697     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 698         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 699     }
 700
 701     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 702     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 703     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 704     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 705         match *qpath {
 706             hir::QPath::Resolved(_, ref path) => path.res,
 707             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 708                 .maybe_typeck_results()
 709                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 710                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 711         }
 712     }
 713
 714     pub fn current_lint_root(&self) -> hir::HirId {
 715         self.last_node_with_lint_attrs
 716     }
 717
 718     /// Check if a `DefId`'s path matches the given absolute type path usage.
 719     ///
 720     /// Anonymous scopes such as `extern` imports are matched with `kw::Invalid`;
 721     /// inherent `impl` blocks are matched with the name of the type.
 722     ///
 723     /// Instead of using this method, it is often preferable to instead use
 724     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 725     /// as paths get invalidated if the target definition moves.
 726     ///
 727     /// # Examples
 728     ///
 729     /// ```rust,ignore (no context or def id available)
 730     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 731     ///     // The given `def_id` is that of an `Option` type
 732     /// }
 733     /// ```
 734     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 735         let names = self.get_def_path(def_id);
 736
 737         names.len() == path.len() && names.into_iter().zip(path.iter()).all(|(a, &b)| a == b)
 738     }
 739
 740     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 741     ///
 742     /// # Examples
 743     ///
 744     /// ```rust,ignore (no context or def id available)
 745     /// let def_path = cx.get_def_path(def_id);
 746     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 747     ///     // The given `def_id` is that of an `Option` type
 748     /// }
 749     /// ```
 750     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 751         pub struct AbsolutePathPrinter<'tcx> {
 752             pub tcx: TyCtxt<'tcx>,
 753         }
 754
 755         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 756             type Error = !;
 757
 758             type Path = Vec<Symbol>;
 759             type Region = ();
 760             type Type = ();
 761             type DynExistential = ();
 762             type Const = ();
 763
 764             fn tcx(&self) -> TyCtxt<'tcx> {
 765                 self.tcx
 766             }
 767
 768             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 769                 Ok(())
 770             }
 771
 772             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 773                 Ok(())
 774             }
 775
 776             fn print_dyn_existential(
 777                 self,
 778                 _predicates: &'tcx ty::List<ty::ExistentialPredicate<'tcx>>,
 779             ) -> Result<Self::DynExistential, Self::Error> {
 780                 Ok(())
 781             }
 782
 783             fn print_const(self, _ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 784                 Ok(())
 785             }
 786
 787             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 788                 Ok(vec![self.tcx.original_crate_name(cnum)])
 789             }
 790
 791             fn path_qualified(
 792                 self,
 793                 self_ty: Ty<'tcx>,
 794                 trait_ref: Option<ty::TraitRef<'tcx>>,
 795             ) -> Result<Self::Path, Self::Error> {
 796                 if trait_ref.is_none() {
 797                     if let ty::Adt(def, substs) = self_ty.kind() {
 798                         return self.print_def_path(def.did, substs);
 799                     }
 800                 }
 801
 802                 // This shouldn't ever be needed, but just in case:
 803                 with_no_trimmed_paths(|| {
 804                     Ok(vec![match trait_ref {
 805                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
 806                         None => Symbol::intern(&format!("<{}>", self_ty)),
 807                     }])
 808                 })
 809             }
 810
 811             fn path_append_impl(
 812                 self,
 813                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 814                 _disambiguated_data: &DisambiguatedDefPathData,
 815                 self_ty: Ty<'tcx>,
 816                 trait_ref: Option<ty::TraitRef<'tcx>>,
 817             ) -> Result<Self::Path, Self::Error> {
 818                 let mut path = print_prefix(self)?;
 819
 820                 // This shouldn't ever be needed, but just in case:
 821                 path.push(match trait_ref {
 822                     Some(trait_ref) => with_no_trimmed_paths(|| {
 823                         Symbol::intern(&format!(
 824                             "<impl {} for {}>",
 825                             trait_ref.print_only_trait_path(),
 826                             self_ty
 827                         ))
 828                     }),
 829                     None => {
 830                         with_no_trimmed_paths(|| Symbol::intern(&format!("<impl {}>", self_ty)))
 831                     }
 832                 });
 833
 834                 Ok(path)
 835             }
 836
 837             fn path_append(
 838                 self,
 839                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 840                 disambiguated_data: &DisambiguatedDefPathData,
 841             ) -> Result<Self::Path, Self::Error> {
 842                 let mut path = print_prefix(self)?;
 843
 844                 // Skip `::{{constructor}}` on tuple/unit structs.
 845                 if let DefPathData::Ctor = disambiguated_data.data {
 846                     return Ok(path);
 847                 }
 848
 849                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
 850                 Ok(path)
 851             }
 852
 853             fn path_generic_args(
 854                 self,
 855                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 856                 _args: &[GenericArg<'tcx>],
 857             ) -> Result<Self::Path, Self::Error> {
 858                 print_prefix(self)
 859             }
 860         }
 861
 862         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
 863     }
 864 }
 865
 866 impl<'tcx> LayoutOf for LateContext<'tcx> {
 867     type Ty = Ty<'tcx>;
 868     type TyAndLayout = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
 869
 870     fn layout_of(&self, ty: Ty<'tcx>) -> Self::TyAndLayout {
 871         self.tcx.layout_of(self.param_env.and(ty))
 872     }
 873 }