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