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