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::{is_known_lint_tool, 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, LayoutOfHelpers, 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_span::lev_distance::find_best_match_for_name;
  42 use rustc_span::{symbol::Symbol, MultiSpan, Span, DUMMY_SP};
  43 use rustc_target::abi;
  44 use tracing::debug;
  45
  46 use std::cell::Cell;
  47 use std::iter;
  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 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  78 #[derive(Debug)]
  79 enum TargetLint {
  80     /// A direct lint target
  81     Id(LintId),
  82
  83     /// Temporary renaming, used for easing migration pain; see #16545
  84     Renamed(String, LintId),
  85
  86     /// Lint with this name existed previously, but has been removed/deprecated.
  87     /// The string argument is the reason for removal.
  88     Removed(String),
  89
  90     /// A lint name that should give no warnings and have no effect.
  91     ///
  92     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  93     Ignored,
  94 }
  95
  96 pub enum FindLintError {
  97     NotFound,
  98     Removed,
  99 }
 100
 101 struct LintAlias {
 102     name: &'static str,
 103     /// Whether deprecation warnings should be suppressed for this alias.
 104     silent: bool,
 105 }
 106
 107 struct LintGroup {
 108     lint_ids: Vec<LintId>,
 109     from_plugin: bool,
 110     depr: Option<LintAlias>,
 111 }
 112
 113 pub enum CheckLintNameResult<'a> {
 114     Ok(&'a [LintId]),
 115     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 116     NoLint(Option<Symbol>),
 117     /// The lint refers to a tool that has not been registered.
 118     NoTool,
 119     /// The lint is either renamed or removed. This is the warning
 120     /// message, and an optional new name (`None` if removed).
 121     Warning(String, Option<String>),
 122     /// The lint is from a tool. If the Option is None, then either
 123     /// the lint does not exist in the tool or the code was not
 124     /// compiled with the tool and therefore the lint was never
 125     /// added to the `LintStore`. Otherwise the `LintId` will be
 126     /// returned as if it where a rustc lint.
 127     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 128 }
 129
 130 impl LintStore {
 131     pub fn new() -> LintStore {
 132         LintStore {
 133             lints: vec![],
 134             pre_expansion_passes: vec![],
 135             early_passes: vec![],
 136             late_passes: vec![],
 137             late_module_passes: vec![],
 138             by_name: Default::default(),
 139             lint_groups: Default::default(),
 140         }
 141     }
 142
 143     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 144         &self.lints
 145     }
 146
 147     pub fn get_lint_groups<'t>(&'t self) -> Vec<(&'static str, Vec<LintId>, bool)> {
 148         self.lint_groups
 149             .iter()
 150             .filter(|(_, LintGroup { depr, .. })| {
 151                 // Don't display deprecated lint groups.
 152                 depr.is_none()
 153             })
 154             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 155                 (*k, lint_ids.clone(), *from_plugin)
 156             })
 157             .collect()
 158     }
 159
 160     pub fn register_early_pass(
 161         &mut self,
 162         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 163     ) {
 164         self.early_passes.push(Box::new(pass));
 165     }
 166
 167     /// Used by clippy.
 168     pub fn register_pre_expansion_pass(
 169         &mut self,
 170         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 171     ) {
 172         self.pre_expansion_passes.push(Box::new(pass));
 173     }
 174
 175     pub fn register_late_pass(
 176         &mut self,
 177         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 178     ) {
 179         self.late_passes.push(Box::new(pass));
 180     }
 181
 182     pub fn register_late_mod_pass(
 183         &mut self,
 184         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 185     ) {
 186         self.late_module_passes.push(Box::new(pass));
 187     }
 188
 189     // Helper method for register_early/late_pass
 190     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 191         for lint in lints {
 192             self.lints.push(lint);
 193
 194             let id = LintId::of(lint);
 195             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 196                 bug!("duplicate specification of lint {}", lint.name_lower())
 197             }
 198
 199             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 200                 if let Some(edition) = reason.edition() {
 201                     self.lint_groups
 202                         .entry(edition.lint_name())
 203                         .or_insert(LintGroup {
 204                             lint_ids: vec![],
 205                             from_plugin: lint.is_plugin,
 206                             depr: None,
 207                         })
 208                         .lint_ids
 209                         .push(id);
 210                 } else {
 211                     // Lints belonging to the `future_incompatible` lint group are lints where a
 212                     // future version of rustc will cause existing code to stop compiling.
 213                     // Lints tied to an edition don't count because they are opt-in.
 214                     self.lint_groups
 215                         .entry("future_incompatible")
 216                         .or_insert(LintGroup {
 217                             lint_ids: vec![],
 218                             from_plugin: lint.is_plugin,
 219                             depr: None,
 220                         })
 221                         .lint_ids
 222                         .push(id);
 223                 }
 224             }
 225         }
 226     }
 227
 228     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 229         self.lint_groups.insert(
 230             alias,
 231             LintGroup {
 232                 lint_ids: vec![],
 233                 from_plugin: false,
 234                 depr: Some(LintAlias { name: lint_name, silent: true }),
 235             },
 236         );
 237     }
 238
 239     pub fn register_group(
 240         &mut self,
 241         from_plugin: bool,
 242         name: &'static str,
 243         deprecated_name: Option<&'static str>,
 244         to: Vec<LintId>,
 245     ) {
 246         let new = self
 247             .lint_groups
 248             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 249             .is_none();
 250         if let Some(deprecated) = deprecated_name {
 251             self.lint_groups.insert(
 252                 deprecated,
 253                 LintGroup {
 254                     lint_ids: vec![],
 255                     from_plugin,
 256                     depr: Some(LintAlias { name, silent: false }),
 257                 },
 258             );
 259         }
 260
 261         if !new {
 262             bug!("duplicate specification of lint group {}", name);
 263         }
 264     }
 265
 266     /// This lint should give no warning and have no effect.
 267     ///
 268     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 269     #[track_caller]
 270     pub fn register_ignored(&mut self, name: &str) {
 271         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 272             bug!("duplicate specification of lint {}", name);
 273         }
 274     }
 275
 276     /// This lint has been renamed; warn about using the new name and apply the lint.
 277     #[track_caller]
 278     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 279         let target = match self.by_name.get(new_name) {
 280             Some(&Id(lint_id)) => lint_id,
 281             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 282         };
 283         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 284     }
 285
 286     pub fn register_removed(&mut self, name: &str, reason: &str) {
 287         self.by_name.insert(name.into(), Removed(reason.into()));
 288     }
 289
 290     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 291         match self.by_name.get(lint_name) {
 292             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 293             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 294             Some(&Removed(_)) => Err(FindLintError::Removed),
 295             Some(&Ignored) => Ok(vec![]),
 296             None => loop {
 297                 return match self.lint_groups.get(lint_name) {
 298                     Some(LintGroup { lint_ids, depr, .. }) => {
 299                         if let Some(LintAlias { name, .. }) = depr {
 300                             lint_name = name;
 301                             continue;
 302                         }
 303                         Ok(lint_ids.clone())
 304                     }
 305                     None => Err(FindLintError::Removed),
 306                 };
 307             },
 308         }
 309     }
 310
 311     /// Checks the validity of lint names derived from the command line.
 312     pub fn check_lint_name_cmdline(
 313         &self,
 314         sess: &Session,
 315         lint_name: &str,
 316         level: Level,
 317         crate_attrs: &[ast::Attribute],
 318     ) {
 319         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 320         if lint_name_only == crate::WARNINGS.name_lower() && level == Level::ForceWarn {
 321             return struct_span_err!(
 322                 sess,
 323                 DUMMY_SP,
 324                 E0602,
 325                 "`{}` lint group is not supported with ´--force-warn´",
 326                 crate::WARNINGS.name_lower()
 327             )
 328             .emit();
 329         }
 330         let db = match self.check_lint_name(sess, lint_name_only, tool_name, crate_attrs) {
 331             CheckLintNameResult::Ok(_) => None,
 332             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 333             CheckLintNameResult::NoLint(suggestion) => {
 334                 let mut err =
 335                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 336
 337                 if let Some(suggestion) = suggestion {
 338                     err.help(&format!("did you mean: `{}`", suggestion));
 339                 }
 340
 341                 Some(err)
 342             }
 343             CheckLintNameResult::Tool(result) => match result {
 344                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 345                     "lint name `{}` is deprecated \
 346                      and does not have an effect anymore. \
 347                      Use: {}",
 348                     lint_name, new_name
 349                 ))),
 350                 _ => None,
 351             },
 352             CheckLintNameResult::NoTool => Some(struct_span_err!(
 353                 sess,
 354                 DUMMY_SP,
 355                 E0602,
 356                 "unknown lint tool: `{}`",
 357                 tool_name.unwrap()
 358             )),
 359         };
 360
 361         if let Some(mut db) = db {
 362             let msg = format!(
 363                 "requested on the command line with `{} {}`",
 364                 match level {
 365                     Level::Allow => "-A",
 366                     Level::Warn => "-W",
 367                     Level::ForceWarn => "--force-warn",
 368                     Level::Deny => "-D",
 369                     Level::Forbid => "-F",
 370                 },
 371                 lint_name
 372             );
 373             db.note(&msg);
 374             db.emit();
 375         }
 376     }
 377
 378     /// True if this symbol represents a lint group name.
 379     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 380         debug!(
 381             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 382             lint_name,
 383             self.lint_groups.keys().collect::<Vec<_>>()
 384         );
 385         let lint_name_str = &*lint_name.as_str();
 386         self.lint_groups.contains_key(&lint_name_str) || {
 387             let warnings_name_str = crate::WARNINGS.name_lower();
 388             lint_name_str == &*warnings_name_str
 389         }
 390     }
 391
 392     /// Checks the name of a lint for its existence, and whether it was
 393     /// renamed or removed. Generates a DiagnosticBuilder containing a
 394     /// warning for renamed and removed lints. This is over both lint
 395     /// names from attributes and those passed on the command line. Since
 396     /// it emits non-fatal warnings and there are *two* lint passes that
 397     /// inspect attributes, this is only run from the late pass to avoid
 398     /// printing duplicate warnings.
 399     pub fn check_lint_name(
 400         &self,
 401         sess: &Session,
 402         lint_name: &str,
 403         tool_name: Option<Symbol>,
 404         crate_attrs: &[ast::Attribute],
 405     ) -> CheckLintNameResult<'_> {
 406         if let Some(tool_name) = tool_name {
 407             if !is_known_lint_tool(tool_name, sess, crate_attrs) {
 408                 return CheckLintNameResult::NoTool;
 409             }
 410         }
 411
 412         let complete_name = if let Some(tool_name) = tool_name {
 413             format!("{}::{}", tool_name, lint_name)
 414         } else {
 415             lint_name.to_string()
 416         };
 417         // If the lint was scoped with `tool::` check if the tool lint exists
 418         if let Some(tool_name) = tool_name {
 419             match self.by_name.get(&complete_name) {
 420                 None => match self.lint_groups.get(&*complete_name) {
 421                     // If the lint isn't registered, there are two possibilities:
 422                     None => {
 423                         // 1. The tool is currently running, so this lint really doesn't exist.
 424                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 425                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 426                         let tool_prefix = format!("{}::", tool_name);
 427                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 428                             self.no_lint_suggestion(&complete_name)
 429                         } else {
 430                             // 2. The tool isn't currently running, so no lints will be registered.
 431                             // To avoid giving a false positive, ignore all unknown lints.
 432                             CheckLintNameResult::Tool(Err((None, String::new())))
 433                         };
 434                     }
 435                     Some(LintGroup { lint_ids, .. }) => {
 436                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 437                     }
 438                 },
 439                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 440                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 441                 // to treat tool_lints and rustc lints different and can use the code below.
 442                 _ => {}
 443             }
 444         }
 445         match self.by_name.get(&complete_name) {
 446             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 447                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 448                 Some(new_name.to_owned()),
 449             ),
 450             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 451                 format!("lint `{}` has been removed: {}", complete_name, reason),
 452                 None,
 453             ),
 454             None => match self.lint_groups.get(&*complete_name) {
 455                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 456                 // variant of this lint
 457                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 458                 Some(LintGroup { lint_ids, depr, .. }) => {
 459                     // Check if the lint group name is deprecated
 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::Ok(&lint_ids)
 464                         } else {
 465                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 466                         };
 467                     }
 468                     CheckLintNameResult::Ok(&lint_ids)
 469                 }
 470             },
 471             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 472             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 473         }
 474     }
 475
 476     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 477         let name_lower = lint_name.to_lowercase();
 478
 479         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 480             // First check if the lint name is (partly) in upper case instead of lower case...
 481             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 482         }
 483         // ...if not, search for lints with a similar name
 484         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 485         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 486         let names: Vec<Symbol> = groups.chain(lints).collect();
 487         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 488         CheckLintNameResult::NoLint(suggestion)
 489     }
 490
 491     fn check_tool_name_for_backwards_compat(
 492         &self,
 493         lint_name: &str,
 494         tool_name: &str,
 495     ) -> CheckLintNameResult<'_> {
 496         let complete_name = format!("{}::{}", tool_name, lint_name);
 497         match self.by_name.get(&complete_name) {
 498             None => match self.lint_groups.get(&*complete_name) {
 499                 // Now we are sure, that this lint exists nowhere
 500                 None => self.no_lint_suggestion(lint_name),
 501                 Some(LintGroup { lint_ids, depr, .. }) => {
 502                     // Reaching this would be weird, but let's cover this case anyway
 503                     if let Some(LintAlias { name, silent }) = depr {
 504                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 505                         return if *silent {
 506                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 507                         } else {
 508                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 509                         };
 510                     }
 511                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 512                 }
 513             },
 514             Some(&Id(ref id)) => {
 515                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 516             }
 517             Some(other) => {
 518                 tracing::debug!("got renamed lint {:?}", other);
 519                 CheckLintNameResult::NoLint(None)
 520             }
 521         }
 522     }
 523 }
 524
 525 /// Context for lint checking after type checking.
 526 pub struct LateContext<'tcx> {
 527     /// Type context we're checking in.
 528     pub tcx: TyCtxt<'tcx>,
 529
 530     /// Current body, or `None` if outside a body.
 531     pub enclosing_body: Option<hir::BodyId>,
 532
 533     /// Type-checking results for the current body. Access using the `typeck_results`
 534     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 535     // FIXME(eddyb) move all the code accessing internal fields like this,
 536     // to this module, to avoid exposing it to lint logic.
 537     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 538
 539     /// Parameter environment for the item we are in.
 540     pub param_env: ty::ParamEnv<'tcx>,
 541
 542     /// Items accessible from the crate being checked.
 543     pub access_levels: &'tcx AccessLevels,
 544
 545     /// The store of registered lints and the lint levels.
 546     pub lint_store: &'tcx LintStore,
 547
 548     pub last_node_with_lint_attrs: hir::HirId,
 549
 550     /// Generic type parameters in scope for the item we are in.
 551     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 552
 553     /// We are only looking at one module
 554     pub only_module: bool,
 555 }
 556
 557 /// Context for lint checking of the AST, after expansion, before lowering to
 558 /// HIR.
 559 pub struct EarlyContext<'a> {
 560     /// Type context we're checking in.
 561     pub sess: &'a Session,
 562
 563     /// The crate being checked.
 564     pub krate: &'a ast::Crate,
 565
 566     pub builder: LintLevelsBuilder<'a>,
 567
 568     /// The store of registered lints and the lint levels.
 569     pub lint_store: &'a LintStore,
 570
 571     pub buffered: LintBuffer,
 572 }
 573
 574 pub trait LintPassObject: Sized {}
 575
 576 impl LintPassObject for EarlyLintPassObject {}
 577
 578 impl LintPassObject for LateLintPassObject {}
 579
 580 pub trait LintContext: Sized {
 581     type PassObject: LintPassObject;
 582
 583     fn sess(&self) -> &Session;
 584     fn lints(&self) -> &LintStore;
 585
 586     fn lookup_with_diagnostics(
 587         &self,
 588         lint: &'static Lint,
 589         span: Option<impl Into<MultiSpan>>,
 590         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 591         diagnostic: BuiltinLintDiagnostics,
 592     ) {
 593         self.lookup(lint, span, |lint| {
 594             // We first generate a blank diagnostic.
 595             let mut db = lint.build("");
 596
 597             // Now, set up surrounding context.
 598             let sess = self.sess();
 599             match diagnostic {
 600                 BuiltinLintDiagnostics::Normal => (),
 601                 BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 602                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 603                         Ok(s) if is_global => {
 604                             (format!("dyn ({})", s), Applicability::MachineApplicable)
 605                         }
 606                         Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 607                         Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
 608                     };
 609                     db.span_suggestion(span, "use `dyn`", sugg, app);
 610                 }
 611                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 612                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 613                         Ok(ref s) => {
 614                             // FIXME(Manishearth) ideally the emitting code
 615                             // can tell us whether or not this is global
 616                             let opt_colon =
 617                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 618
 619                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 620                         }
 621                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 622                     };
 623                     db.span_suggestion(span, "use `crate`", sugg, app);
 624                 }
 625                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 626                     db.span_label(
 627                         span,
 628                         "names from parent modules are not accessible without an explicit import",
 629                     );
 630                 }
 631                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 632                     span_def,
 633                 ) => {
 634                     db.span_note(span_def, "the macro is defined here");
 635                 }
 636                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 637                     n,
 638                     path_span,
 639                     incl_angl_brckt,
 640                     insertion_span,
 641                     anon_lts,
 642                 ) => {
 643                     add_elided_lifetime_in_path_suggestion(
 644                         sess.source_map(),
 645                         &mut db,
 646                         n,
 647                         path_span,
 648                         incl_angl_brckt,
 649                         insertion_span,
 650                         anon_lts,
 651                     );
 652                 }
 653                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 654                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 655                 }
 656                 BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
 657                     if !replaces.is_empty() {
 658                         db.tool_only_multipart_suggestion(
 659                             &message,
 660                             replaces,
 661                             Applicability::MachineApplicable,
 662                         );
 663                     }
 664                 }
 665                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 666                     for (span, is_imported) in spans {
 667                         let introduced = if is_imported { "imported" } else { "defined" };
 668                         db.span_label(
 669                             span,
 670                             format!("the item `{}` is already {} here", ident, introduced),
 671                         );
 672                     }
 673                 }
 674                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 675                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 676                 }
 677                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 678                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 679                     db.help("to document an item produced by a macro, \
 680                                   the macro must produce the documentation as part of its expansion");
 681                 }
 682                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 683                     db.span_suggestion(span, "remove `mut` from the parameter", ident.to_string(), Applicability::MachineApplicable);
 684                 }
 685                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 686                     db.span_label(span, "ABI should be specified here");
 687                     db.help(&format!("the default ABI is {}", default_abi.name()));
 688                 }
 689                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 690                     db.span_label(span, "the attribute is introduced here");
 691                 }
 692                 BuiltinLintDiagnostics::ExternDepSpec(krate, loc) => {
 693                     let json = match loc {
 694                         ExternDepSpec::Json(json) => {
 695                             db.help(&format!("remove unnecessary dependency `{}`", krate));
 696                             json
 697                         }
 698                         ExternDepSpec::Raw(raw) => {
 699                             db.help(&format!("remove unnecessary dependency `{}` at `{}`", krate, raw));
 700                             db.span_suggestion_with_style(
 701                                 DUMMY_SP,
 702                                 "raw extern location",
 703                                 raw.clone(),
 704                                 Applicability::Unspecified,
 705                                 SuggestionStyle::CompletelyHidden,
 706                             );
 707                             Json::String(raw)
 708                         }
 709                     };
 710                     db.tool_only_suggestion_with_metadata(
 711                         "json extern location",
 712                         Applicability::Unspecified,
 713                         json
 714                     );
 715                 }
 716                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 717                     db.note(&note);
 718                 }
 719                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 720                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 721                 }
 722                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 723                     db.span_label(span, "unknown prefix");
 724                     db.span_suggestion_verbose(
 725                         span.shrink_to_hi(),
 726                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 727                         " ".into(),
 728                         Applicability::MachineApplicable,
 729                     );
 730                 }
 731                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 732                     attr_name,
 733                     macro_name,
 734                     invoc_span
 735                 } => {
 736                     db.span_note(
 737                         invoc_span,
 738                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 739                     );
 740                 }
 741                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 742                     if is_trailing {
 743                         db.note("macro invocations at the end of a block are treated as expressions");
 744                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 745                     }
 746                 }
 747                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 748                     db.multipart_suggestion(
 749                         "wrap this expression in parentheses",
 750                         vec![(span.shrink_to_lo(), "(".to_string()),
 751                              (span.shrink_to_hi(), ")".to_string())],
 752                         Applicability::MachineApplicable
 753                     );
 754                 }
 755                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 756                     db.help(&help);
 757                     db.note("see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information");
 758                 }
 759             }
 760             // Rewrap `db`, and pass control to the user.
 761             decorate(LintDiagnosticBuilder::new(db));
 762         });
 763     }
 764
 765     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 766     // set the span in their `decorate` function (preferably using set_span).
 767     fn lookup<S: Into<MultiSpan>>(
 768         &self,
 769         lint: &'static Lint,
 770         span: Option<S>,
 771         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 772     );
 773
 774     fn struct_span_lint<S: Into<MultiSpan>>(
 775         &self,
 776         lint: &'static Lint,
 777         span: S,
 778         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 779     ) {
 780         self.lookup(lint, Some(span), decorate);
 781     }
 782     /// Emit a lint at the appropriate level, with no associated span.
 783     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 784         self.lookup(lint, None as Option<Span>, decorate);
 785     }
 786 }
 787
 788 impl<'a> EarlyContext<'a> {
 789     pub fn new(
 790         sess: &'a Session,
 791         lint_store: &'a LintStore,
 792         krate: &'a ast::Crate,
 793         crate_attrs: &'a [ast::Attribute],
 794         buffered: LintBuffer,
 795         warn_about_weird_lints: bool,
 796     ) -> EarlyContext<'a> {
 797         EarlyContext {
 798             sess,
 799             krate,
 800             lint_store,
 801             builder: LintLevelsBuilder::new(sess, warn_about_weird_lints, lint_store, crate_attrs),
 802             buffered,
 803         }
 804     }
 805 }
 806
 807 impl LintContext for LateContext<'_> {
 808     type PassObject = LateLintPassObject;
 809
 810     /// Gets the overall compiler `Session` object.
 811     fn sess(&self) -> &Session {
 812         &self.tcx.sess
 813     }
 814
 815     fn lints(&self) -> &LintStore {
 816         &*self.lint_store
 817     }
 818
 819     fn lookup<S: Into<MultiSpan>>(
 820         &self,
 821         lint: &'static Lint,
 822         span: Option<S>,
 823         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 824     ) {
 825         let hir_id = self.last_node_with_lint_attrs;
 826
 827         match span {
 828             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 829             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 830         }
 831     }
 832 }
 833
 834 impl LintContext for EarlyContext<'_> {
 835     type PassObject = EarlyLintPassObject;
 836
 837     /// Gets the overall compiler `Session` object.
 838     fn sess(&self) -> &Session {
 839         &self.sess
 840     }
 841
 842     fn lints(&self) -> &LintStore {
 843         &*self.lint_store
 844     }
 845
 846     fn lookup<S: Into<MultiSpan>>(
 847         &self,
 848         lint: &'static Lint,
 849         span: Option<S>,
 850         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 851     ) {
 852         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 853     }
 854 }
 855
 856 impl<'tcx> LateContext<'tcx> {
 857     /// Gets the type-checking results for the current body,
 858     /// or `None` if outside a body.
 859     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 860         self.cached_typeck_results.get().or_else(|| {
 861             self.enclosing_body.map(|body| {
 862                 let typeck_results = self.tcx.typeck_body(body);
 863                 self.cached_typeck_results.set(Some(typeck_results));
 864                 typeck_results
 865             })
 866         })
 867     }
 868
 869     /// Gets the type-checking results for the current body.
 870     /// As this will ICE if called outside bodies, only call when working with
 871     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 872     #[track_caller]
 873     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 874         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 875     }
 876
 877     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 878     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 879     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 880     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 881         match *qpath {
 882             hir::QPath::Resolved(_, ref path) => path.res,
 883             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 884                 .maybe_typeck_results()
 885                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
 886                 .or_else(|| {
 887                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
 888                         Some(self.tcx.typeck(id.owner))
 889                     } else {
 890                         None
 891                     }
 892                 })
 893                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 894                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 895         }
 896     }
 897
 898     /// Check if a `DefId`'s path matches the given absolute type path usage.
 899     ///
 900     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
 901     /// inherent `impl` blocks are matched with the name of the type.
 902     ///
 903     /// Instead of using this method, it is often preferable to instead use
 904     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 905     /// as paths get invalidated if the target definition moves.
 906     ///
 907     /// # Examples
 908     ///
 909     /// ```rust,ignore (no context or def id available)
 910     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 911     ///     // The given `def_id` is that of an `Option` type
 912     /// }
 913     /// ```
 914     ///
 915     /// Used by clippy, but should be replaced by diagnostic items eventually.
 916     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 917         let names = self.get_def_path(def_id);
 918
 919         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
 920     }
 921
 922     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 923     ///
 924     /// # Examples
 925     ///
 926     /// ```rust,ignore (no context or def id available)
 927     /// let def_path = cx.get_def_path(def_id);
 928     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 929     ///     // The given `def_id` is that of an `Option` type
 930     /// }
 931     /// ```
 932     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 933         pub struct AbsolutePathPrinter<'tcx> {
 934             pub tcx: TyCtxt<'tcx>,
 935         }
 936
 937         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 938             type Error = !;
 939
 940             type Path = Vec<Symbol>;
 941             type Region = ();
 942             type Type = ();
 943             type DynExistential = ();
 944             type Const = ();
 945
 946             fn tcx(&self) -> TyCtxt<'tcx> {
 947                 self.tcx
 948             }
 949
 950             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 951                 Ok(())
 952             }
 953
 954             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 955                 Ok(())
 956             }
 957
 958             fn print_dyn_existential(
 959                 self,
 960                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
 961             ) -> Result<Self::DynExistential, Self::Error> {
 962                 Ok(())
 963             }
 964
 965             fn print_const(self, _ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 966                 Ok(())
 967             }
 968
 969             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 970                 Ok(vec![self.tcx.crate_name(cnum)])
 971             }
 972
 973             fn path_qualified(
 974                 self,
 975                 self_ty: Ty<'tcx>,
 976                 trait_ref: Option<ty::TraitRef<'tcx>>,
 977             ) -> Result<Self::Path, Self::Error> {
 978                 if trait_ref.is_none() {
 979                     if let ty::Adt(def, substs) = self_ty.kind() {
 980                         return self.print_def_path(def.did, substs);
 981                     }
 982                 }
 983
 984                 // This shouldn't ever be needed, but just in case:
 985                 with_no_trimmed_paths(|| {
 986                     Ok(vec![match trait_ref {
 987                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
 988                         None => Symbol::intern(&format!("<{}>", self_ty)),
 989                     }])
 990                 })
 991             }
 992
 993             fn path_append_impl(
 994                 self,
 995                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 996                 _disambiguated_data: &DisambiguatedDefPathData,
 997                 self_ty: Ty<'tcx>,
 998                 trait_ref: Option<ty::TraitRef<'tcx>>,
 999             ) -> Result<Self::Path, Self::Error> {
1000                 let mut path = print_prefix(self)?;
1001
1002                 // This shouldn't ever be needed, but just in case:
1003                 path.push(match trait_ref {
1004                     Some(trait_ref) => with_no_trimmed_paths(|| {
1005                         Symbol::intern(&format!(
1006                             "<impl {} for {}>",
1007                             trait_ref.print_only_trait_path(),
1008                             self_ty
1009                         ))
1010                     }),
1011                     None => {
1012                         with_no_trimmed_paths(|| Symbol::intern(&format!("<impl {}>", self_ty)))
1013                     }
1014                 });
1015
1016                 Ok(path)
1017             }
1018
1019             fn path_append(
1020                 self,
1021                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1022                 disambiguated_data: &DisambiguatedDefPathData,
1023             ) -> Result<Self::Path, Self::Error> {
1024                 let mut path = print_prefix(self)?;
1025
1026                 // Skip `::{{constructor}}` on tuple/unit structs.
1027                 if let DefPathData::Ctor = disambiguated_data.data {
1028                     return Ok(path);
1029                 }
1030
1031                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1032                 Ok(path)
1033             }
1034
1035             fn path_generic_args(
1036                 self,
1037                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1038                 _args: &[GenericArg<'tcx>],
1039             ) -> Result<Self::Path, Self::Error> {
1040                 print_prefix(self)
1041             }
1042         }
1043
1044         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1045     }
1046 }
1047
1048 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1049     #[inline]
1050     fn data_layout(&self) -> &abi::TargetDataLayout {
1051         &self.tcx.data_layout
1052     }
1053 }
1054
1055 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1056     #[inline]
1057     fn tcx(&self) -> TyCtxt<'tcx> {
1058         self.tcx
1059     }
1060 }
1061
1062 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1063     #[inline]
1064     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1065         self.param_env
1066     }
1067 }
1068
1069 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1070     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1071
1072     #[inline]
1073     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1074         err
1075     }
1076 }
1077
1078 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1079     match lint_name.split_once("::") {
1080         Some((tool_name, lint_name)) => {
1081             let tool_name = Symbol::intern(tool_name);
1082
1083             (Some(tool_name), lint_name)
1084         }
1085         None => (None, lint_name),
1086     }
1087 }