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 ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
  22 use rustc_ast as ast;
  23 use rustc_data_structures::fx::FxHashMap;
  24 use rustc_data_structures::sync;
  25 use rustc_errors::{
  26     add_elided_lifetime_in_path_suggestion, struct_span_err, Applicability, SuggestionStyle,
  27 };
  28 use rustc_hir as hir;
  29 use rustc_hir::def::Res;
  30 use rustc_hir::def_id::{CrateNum, DefId};
  31 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  32 use rustc_middle::lint::LintDiagnosticBuilder;
  33 use rustc_middle::middle::privacy::AccessLevels;
  34 use rustc_middle::middle::stability;
  35 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  36 use rustc_middle::ty::print::with_no_trimmed_paths;
  37 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, Ty, TyCtxt};
  38 use rustc_serialize::json::Json;
  39 use rustc_session::lint::{BuiltinLintDiagnostics, ExternDepSpec};
  40 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  41 use rustc_session::Session;
  42 use rustc_span::lev_distance::find_best_match_for_name;
  43 use rustc_span::{symbol::Symbol, BytePos, MultiSpan, Span, DUMMY_SP};
  44 use rustc_target::abi;
  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 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  79 #[derive(Debug)]
  80 enum TargetLint {
  81     /// A direct lint target
  82     Id(LintId),
  83
  84     /// Temporary renaming, used for easing migration pain; see #16545
  85     Renamed(String, LintId),
  86
  87     /// Lint with this name existed previously, but has been removed/deprecated.
  88     /// The string argument is the reason for removal.
  89     Removed(String),
  90
  91     /// A lint name that should give no warnings and have no effect.
  92     ///
  93     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  94     Ignored,
  95 }
  96
  97 pub enum FindLintError {
  98     NotFound,
  99     Removed,
 100 }
 101
 102 struct LintAlias {
 103     name: &'static str,
 104     /// Whether deprecation warnings should be suppressed for this alias.
 105     silent: bool,
 106 }
 107
 108 struct LintGroup {
 109     lint_ids: Vec<LintId>,
 110     from_plugin: bool,
 111     depr: Option<LintAlias>,
 112 }
 113
 114 pub enum CheckLintNameResult<'a> {
 115     Ok(&'a [LintId]),
 116     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 117     NoLint(Option<Symbol>),
 118     /// The lint refers to a tool that has not been registered.
 119     NoTool,
 120     /// The lint is either renamed or removed. This is the warning
 121     /// message, and an optional new name (`None` if removed).
 122     Warning(String, Option<String>),
 123     /// The lint is from a tool. If the Option is None, then either
 124     /// the lint does not exist in the tool or the code was not
 125     /// compiled with the tool and therefore the lint was never
 126     /// added to the `LintStore`. Otherwise the `LintId` will be
 127     /// returned as if it where a rustc lint.
 128     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 129 }
 130
 131 impl LintStore {
 132     pub fn new() -> LintStore {
 133         LintStore {
 134             lints: vec![],
 135             pre_expansion_passes: vec![],
 136             early_passes: vec![],
 137             late_passes: vec![],
 138             late_module_passes: vec![],
 139             by_name: Default::default(),
 140             lint_groups: Default::default(),
 141         }
 142     }
 143
 144     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 145         &self.lints
 146     }
 147
 148     pub fn get_lint_groups<'t>(&'t self) -> Vec<(&'static str, Vec<LintId>, bool)> {
 149         self.lint_groups
 150             .iter()
 151             .filter(|(_, LintGroup { depr, .. })| {
 152                 // Don't display deprecated lint groups.
 153                 depr.is_none()
 154             })
 155             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 156                 (*k, lint_ids.clone(), *from_plugin)
 157             })
 158             .collect()
 159     }
 160
 161     pub fn register_early_pass(
 162         &mut self,
 163         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 164     ) {
 165         self.early_passes.push(Box::new(pass));
 166     }
 167
 168     /// Used by clippy.
 169     pub fn register_pre_expansion_pass(
 170         &mut self,
 171         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 172     ) {
 173         self.pre_expansion_passes.push(Box::new(pass));
 174     }
 175
 176     pub fn register_late_pass(
 177         &mut self,
 178         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 179     ) {
 180         self.late_passes.push(Box::new(pass));
 181     }
 182
 183     pub fn register_late_mod_pass(
 184         &mut self,
 185         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 186     ) {
 187         self.late_module_passes.push(Box::new(pass));
 188     }
 189
 190     // Helper method for register_early/late_pass
 191     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 192         for lint in lints {
 193             self.lints.push(lint);
 194
 195             let id = LintId::of(lint);
 196             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 197                 bug!("duplicate specification of lint {}", lint.name_lower())
 198             }
 199
 200             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 201                 if let Some(edition) = reason.edition() {
 202                     self.lint_groups
 203                         .entry(edition.lint_name())
 204                         .or_insert(LintGroup {
 205                             lint_ids: vec![],
 206                             from_plugin: lint.is_plugin,
 207                             depr: None,
 208                         })
 209                         .lint_ids
 210                         .push(id);
 211                 } else {
 212                     // Lints belonging to the `future_incompatible` lint group are lints where a
 213                     // future version of rustc will cause existing code to stop compiling.
 214                     // Lints tied to an edition don't count because they are opt-in.
 215                     self.lint_groups
 216                         .entry("future_incompatible")
 217                         .or_insert(LintGroup {
 218                             lint_ids: vec![],
 219                             from_plugin: lint.is_plugin,
 220                             depr: None,
 221                         })
 222                         .lint_ids
 223                         .push(id);
 224                 }
 225             }
 226         }
 227     }
 228
 229     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 230         self.lint_groups.insert(
 231             alias,
 232             LintGroup {
 233                 lint_ids: vec![],
 234                 from_plugin: false,
 235                 depr: Some(LintAlias { name: lint_name, silent: true }),
 236             },
 237         );
 238     }
 239
 240     pub fn register_group(
 241         &mut self,
 242         from_plugin: bool,
 243         name: &'static str,
 244         deprecated_name: Option<&'static str>,
 245         to: Vec<LintId>,
 246     ) {
 247         let new = self
 248             .lint_groups
 249             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 250             .is_none();
 251         if let Some(deprecated) = deprecated_name {
 252             self.lint_groups.insert(
 253                 deprecated,
 254                 LintGroup {
 255                     lint_ids: vec![],
 256                     from_plugin,
 257                     depr: Some(LintAlias { name, silent: false }),
 258                 },
 259             );
 260         }
 261
 262         if !new {
 263             bug!("duplicate specification of lint group {}", name);
 264         }
 265     }
 266
 267     /// This lint should give no warning and have no effect.
 268     ///
 269     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 270     #[track_caller]
 271     pub fn register_ignored(&mut self, name: &str) {
 272         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 273             bug!("duplicate specification of lint {}", name);
 274         }
 275     }
 276
 277     /// This lint has been renamed; warn about using the new name and apply the lint.
 278     #[track_caller]
 279     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 280         let target = match self.by_name.get(new_name) {
 281             Some(&Id(lint_id)) => lint_id,
 282             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 283         };
 284         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 285     }
 286
 287     pub fn register_removed(&mut self, name: &str, reason: &str) {
 288         self.by_name.insert(name.into(), Removed(reason.into()));
 289     }
 290
 291     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 292         match self.by_name.get(lint_name) {
 293             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 294             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 295             Some(&Removed(_)) => Err(FindLintError::Removed),
 296             Some(&Ignored) => Ok(vec![]),
 297             None => loop {
 298                 return match self.lint_groups.get(lint_name) {
 299                     Some(LintGroup { lint_ids, depr, .. }) => {
 300                         if let Some(LintAlias { name, .. }) = depr {
 301                             lint_name = name;
 302                             continue;
 303                         }
 304                         Ok(lint_ids.clone())
 305                     }
 306                     None => Err(FindLintError::Removed),
 307                 };
 308             },
 309         }
 310     }
 311
 312     /// Checks the validity of lint names derived from the command line.
 313     pub fn check_lint_name_cmdline(
 314         &self,
 315         sess: &Session,
 316         lint_name: &str,
 317         level: Level,
 318         crate_attrs: &[ast::Attribute],
 319     ) {
 320         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 321         if lint_name_only == crate::WARNINGS.name_lower() && level == Level::ForceWarn {
 322             return struct_span_err!(
 323                 sess,
 324                 DUMMY_SP,
 325                 E0602,
 326                 "`{}` lint group is not supported with ´--force-warn´",
 327                 crate::WARNINGS.name_lower()
 328             )
 329             .emit();
 330         }
 331         let db = match self.check_lint_name(sess, lint_name_only, tool_name, crate_attrs) {
 332             CheckLintNameResult::Ok(_) => None,
 333             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 334             CheckLintNameResult::NoLint(suggestion) => {
 335                 let mut err =
 336                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 337
 338                 if let Some(suggestion) = suggestion {
 339                     err.help(&format!("did you mean: `{}`", suggestion));
 340                 }
 341
 342                 Some(err)
 343             }
 344             CheckLintNameResult::Tool(result) => match result {
 345                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 346                     "lint name `{}` is deprecated \
 347                      and does not have an effect anymore. \
 348                      Use: {}",
 349                     lint_name, new_name
 350                 ))),
 351                 _ => None,
 352             },
 353             CheckLintNameResult::NoTool => Some(struct_span_err!(
 354                 sess,
 355                 DUMMY_SP,
 356                 E0602,
 357                 "unknown lint tool: `{}`",
 358                 tool_name.unwrap()
 359             )),
 360         };
 361
 362         if let Some(mut db) = db {
 363             let msg = format!(
 364                 "requested on the command line with `{} {}`",
 365                 match level {
 366                     Level::Allow => "-A",
 367                     Level::Warn => "-W",
 368                     Level::ForceWarn => "--force-warn",
 369                     Level::Deny => "-D",
 370                     Level::Forbid => "-F",
 371                 },
 372                 lint_name
 373             );
 374             db.note(&msg);
 375             db.emit();
 376         }
 377     }
 378
 379     /// True if this symbol represents a lint group name.
 380     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 381         debug!(
 382             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 383             lint_name,
 384             self.lint_groups.keys().collect::<Vec<_>>()
 385         );
 386         let lint_name_str = &*lint_name.as_str();
 387         self.lint_groups.contains_key(&lint_name_str) || {
 388             let warnings_name_str = crate::WARNINGS.name_lower();
 389             lint_name_str == &*warnings_name_str
 390         }
 391     }
 392
 393     /// Checks the name of a lint for its existence, and whether it was
 394     /// renamed or removed. Generates a DiagnosticBuilder containing a
 395     /// warning for renamed and removed lints. This is over both lint
 396     /// names from attributes and those passed on the command line. Since
 397     /// it emits non-fatal warnings and there are *two* lint passes that
 398     /// inspect attributes, this is only run from the late pass to avoid
 399     /// printing duplicate warnings.
 400     pub fn check_lint_name(
 401         &self,
 402         sess: &Session,
 403         lint_name: &str,
 404         tool_name: Option<Symbol>,
 405         crate_attrs: &[ast::Attribute],
 406     ) -> CheckLintNameResult<'_> {
 407         if let Some(tool_name) = tool_name {
 408             if !is_known_lint_tool(tool_name, sess, crate_attrs) {
 409                 return CheckLintNameResult::NoTool;
 410             }
 411         }
 412
 413         let complete_name = if let Some(tool_name) = tool_name {
 414             format!("{}::{}", tool_name, lint_name)
 415         } else {
 416             lint_name.to_string()
 417         };
 418         // If the lint was scoped with `tool::` check if the tool lint exists
 419         if let Some(tool_name) = tool_name {
 420             match self.by_name.get(&complete_name) {
 421                 None => match self.lint_groups.get(&*complete_name) {
 422                     // If the lint isn't registered, there are two possibilities:
 423                     None => {
 424                         // 1. The tool is currently running, so this lint really doesn't exist.
 425                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 426                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 427                         let tool_prefix = format!("{}::", tool_name);
 428                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 429                             self.no_lint_suggestion(&complete_name)
 430                         } else {
 431                             // 2. The tool isn't currently running, so no lints will be registered.
 432                             // To avoid giving a false positive, ignore all unknown lints.
 433                             CheckLintNameResult::Tool(Err((None, String::new())))
 434                         };
 435                     }
 436                     Some(LintGroup { lint_ids, .. }) => {
 437                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 438                     }
 439                 },
 440                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 441                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 442                 // to treat tool_lints and rustc lints different and can use the code below.
 443                 _ => {}
 444             }
 445         }
 446         match self.by_name.get(&complete_name) {
 447             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 448                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 449                 Some(new_name.to_owned()),
 450             ),
 451             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 452                 format!("lint `{}` has been removed: {}", complete_name, reason),
 453                 None,
 454             ),
 455             None => match self.lint_groups.get(&*complete_name) {
 456                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 457                 // variant of this lint
 458                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 459                 Some(LintGroup { lint_ids, depr, .. }) => {
 460                     // Check if the lint group name is deprecated
 461                     if let Some(LintAlias { name, silent }) = depr {
 462                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 463                         return if *silent {
 464                             CheckLintNameResult::Ok(&lint_ids)
 465                         } else {
 466                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 467                         };
 468                     }
 469                     CheckLintNameResult::Ok(&lint_ids)
 470                 }
 471             },
 472             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 473             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 474         }
 475     }
 476
 477     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 478         let name_lower = lint_name.to_lowercase();
 479
 480         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 481             // First check if the lint name is (partly) in upper case instead of lower case...
 482             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 483         }
 484         // ...if not, search for lints with a similar name
 485         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 486         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 487         let names: Vec<Symbol> = groups.chain(lints).collect();
 488         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 489         CheckLintNameResult::NoLint(suggestion)
 490     }
 491
 492     fn check_tool_name_for_backwards_compat(
 493         &self,
 494         lint_name: &str,
 495         tool_name: &str,
 496     ) -> CheckLintNameResult<'_> {
 497         let complete_name = format!("{}::{}", tool_name, lint_name);
 498         match self.by_name.get(&complete_name) {
 499             None => match self.lint_groups.get(&*complete_name) {
 500                 // Now we are sure, that this lint exists nowhere
 501                 None => self.no_lint_suggestion(lint_name),
 502                 Some(LintGroup { lint_ids, depr, .. }) => {
 503                     // Reaching this would be weird, but let's cover this case anyway
 504                     if let Some(LintAlias { name, silent }) = depr {
 505                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 506                         return if *silent {
 507                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 508                         } else {
 509                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 510                         };
 511                     }
 512                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 513                 }
 514             },
 515             Some(&Id(ref id)) => {
 516                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 517             }
 518             Some(other) => {
 519                 tracing::debug!("got renamed lint {:?}", other);
 520                 CheckLintNameResult::NoLint(None)
 521             }
 522         }
 523     }
 524 }
 525
 526 /// Context for lint checking after type checking.
 527 pub struct LateContext<'tcx> {
 528     /// Type context we're checking in.
 529     pub tcx: TyCtxt<'tcx>,
 530
 531     /// Current body, or `None` if outside a body.
 532     pub enclosing_body: Option<hir::BodyId>,
 533
 534     /// Type-checking results for the current body. Access using the `typeck_results`
 535     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 536     // FIXME(eddyb) move all the code accessing internal fields like this,
 537     // to this module, to avoid exposing it to lint logic.
 538     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 539
 540     /// Parameter environment for the item we are in.
 541     pub param_env: ty::ParamEnv<'tcx>,
 542
 543     /// Items accessible from the crate being checked.
 544     pub access_levels: &'tcx AccessLevels,
 545
 546     /// The store of registered lints and the lint levels.
 547     pub lint_store: &'tcx LintStore,
 548
 549     pub last_node_with_lint_attrs: hir::HirId,
 550
 551     /// Generic type parameters in scope for the item we are in.
 552     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 553
 554     /// We are only looking at one module
 555     pub only_module: bool,
 556 }
 557
 558 /// Context for lint checking of the AST, after expansion, before lowering to
 559 /// HIR.
 560 pub struct EarlyContext<'a> {
 561     /// Type context we're checking in.
 562     pub sess: &'a Session,
 563
 564     /// The crate being checked.
 565     pub krate: &'a ast::Crate,
 566
 567     pub builder: LintLevelsBuilder<'a>,
 568
 569     /// The store of registered lints and the lint levels.
 570     pub lint_store: &'a LintStore,
 571
 572     pub buffered: LintBuffer,
 573 }
 574
 575 pub trait LintPassObject: Sized {}
 576
 577 impl LintPassObject for EarlyLintPassObject {}
 578
 579 impl LintPassObject for LateLintPassObject {}
 580
 581 pub trait LintContext: Sized {
 582     type PassObject: LintPassObject;
 583
 584     fn sess(&self) -> &Session;
 585     fn lints(&self) -> &LintStore;
 586
 587     fn lookup_with_diagnostics(
 588         &self,
 589         lint: &'static Lint,
 590         span: Option<impl Into<MultiSpan>>,
 591         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 592         diagnostic: BuiltinLintDiagnostics,
 593     ) {
 594         self.lookup(lint, span, |lint| {
 595             // We first generate a blank diagnostic.
 596             let mut db = lint.build("");
 597
 598             // Now, set up surrounding context.
 599             let sess = self.sess();
 600             match diagnostic {
 601                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
 602                     let spans: Vec<_> = content
 603                         .char_indices()
 604                         .filter_map(|(i, c)| {
 605                             TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
 606                                 let lo = span.lo() + BytePos(2 + i as u32);
 607                                 (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
 608                             })
 609                         })
 610                         .collect();
 611                     let (an, s) = match spans.len() {
 612                         1 => ("an ", ""),
 613                         _ => ("", "s"),
 614                     };
 615                     db.span_label(span, &format!(
 616                         "this comment contains {}invisible unicode text flow control codepoint{}",
 617                         an,
 618                         s,
 619                     ));
 620                     for (c, span) in &spans {
 621                         db.span_label(*span, format!("{:?}", c));
 622                     }
 623                     db.note(
 624                         "these kind of unicode codepoints change the way text flows on \
 625                          applications that support them, but can cause confusion because they \
 626                          change the order of characters on the screen",
 627                     );
 628                     if !spans.is_empty() {
 629                         db.multipart_suggestion_with_style(
 630                             "if their presence wasn't intentional, you can remove them",
 631                             spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
 632                             Applicability::MachineApplicable,
 633                             SuggestionStyle::HideCodeAlways,
 634                         );
 635                     }
 636                 },
 637                 BuiltinLintDiagnostics::Normal => (),
 638                 BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 639                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 640                         Ok(s) if is_global => {
 641                             (format!("dyn ({})", s), Applicability::MachineApplicable)
 642                         }
 643                         Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 644                         Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
 645                     };
 646                     db.span_suggestion(span, "use `dyn`", sugg, app);
 647                 }
 648                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 649                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 650                         Ok(ref s) => {
 651                             // FIXME(Manishearth) ideally the emitting code
 652                             // can tell us whether or not this is global
 653                             let opt_colon =
 654                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 655
 656                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 657                         }
 658                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 659                     };
 660                     db.span_suggestion(span, "use `crate`", sugg, app);
 661                 }
 662                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 663                     db.span_label(
 664                         span,
 665                         "names from parent modules are not accessible without an explicit import",
 666                     );
 667                 }
 668                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 669                     span_def,
 670                 ) => {
 671                     db.span_note(span_def, "the macro is defined here");
 672                 }
 673                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 674                     n,
 675                     path_span,
 676                     incl_angl_brckt,
 677                     insertion_span,
 678                     anon_lts,
 679                 ) => {
 680                     add_elided_lifetime_in_path_suggestion(
 681                         sess.source_map(),
 682                         &mut db,
 683                         n,
 684                         path_span,
 685                         incl_angl_brckt,
 686                         insertion_span,
 687                         anon_lts,
 688                     );
 689                 }
 690                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 691                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 692                 }
 693                 BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
 694                     if !replaces.is_empty() {
 695                         db.tool_only_multipart_suggestion(
 696                             &message,
 697                             replaces,
 698                             Applicability::MachineApplicable,
 699                         );
 700                     }
 701                 }
 702                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 703                     for (span, is_imported) in spans {
 704                         let introduced = if is_imported { "imported" } else { "defined" };
 705                         db.span_label(
 706                             span,
 707                             format!("the item `{}` is already {} here", ident, introduced),
 708                         );
 709                     }
 710                 }
 711                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 712                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 713                 }
 714                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 715                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 716                     db.help("to document an item produced by a macro, \
 717                                   the macro must produce the documentation as part of its expansion");
 718                 }
 719                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 720                     db.span_suggestion(span, "remove `mut` from the parameter", ident.to_string(), Applicability::MachineApplicable);
 721                 }
 722                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 723                     db.span_label(span, "ABI should be specified here");
 724                     db.help(&format!("the default ABI is {}", default_abi.name()));
 725                 }
 726                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 727                     db.span_label(span, "the attribute is introduced here");
 728                 }
 729                 BuiltinLintDiagnostics::ExternDepSpec(krate, loc) => {
 730                     let json = match loc {
 731                         ExternDepSpec::Json(json) => {
 732                             db.help(&format!("remove unnecessary dependency `{}`", krate));
 733                             json
 734                         }
 735                         ExternDepSpec::Raw(raw) => {
 736                             db.help(&format!("remove unnecessary dependency `{}` at `{}`", krate, raw));
 737                             db.span_suggestion_with_style(
 738                                 DUMMY_SP,
 739                                 "raw extern location",
 740                                 raw.clone(),
 741                                 Applicability::Unspecified,
 742                                 SuggestionStyle::CompletelyHidden,
 743                             );
 744                             Json::String(raw)
 745                         }
 746                     };
 747                     db.tool_only_suggestion_with_metadata(
 748                         "json extern location",
 749                         Applicability::Unspecified,
 750                         json
 751                     );
 752                 }
 753                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 754                     db.note(&note);
 755                 }
 756                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 757                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 758                 }
 759                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 760                     db.span_label(span, "unknown prefix");
 761                     db.span_suggestion_verbose(
 762                         span.shrink_to_hi(),
 763                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 764                         " ".into(),
 765                         Applicability::MachineApplicable,
 766                     );
 767                 }
 768                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 769                     attr_name,
 770                     macro_name,
 771                     invoc_span
 772                 } => {
 773                     db.span_note(
 774                         invoc_span,
 775                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 776                     );
 777                 }
 778                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 779                     if is_trailing {
 780                         db.note("macro invocations at the end of a block are treated as expressions");
 781                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 782                     }
 783                 }
 784                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 785                     db.multipart_suggestion(
 786                         "wrap this expression in parentheses",
 787                         vec![(span.shrink_to_lo(), "(".to_string()),
 788                              (span.shrink_to_hi(), ")".to_string())],
 789                         Applicability::MachineApplicable
 790                     );
 791                 }
 792                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 793                     db.help(&help);
 794                     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");
 795                 }
 796             }
 797             // Rewrap `db`, and pass control to the user.
 798             decorate(LintDiagnosticBuilder::new(db));
 799         });
 800     }
 801
 802     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 803     // set the span in their `decorate` function (preferably using set_span).
 804     fn lookup<S: Into<MultiSpan>>(
 805         &self,
 806         lint: &'static Lint,
 807         span: Option<S>,
 808         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 809     );
 810
 811     fn struct_span_lint<S: Into<MultiSpan>>(
 812         &self,
 813         lint: &'static Lint,
 814         span: S,
 815         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 816     ) {
 817         self.lookup(lint, Some(span), decorate);
 818     }
 819     /// Emit a lint at the appropriate level, with no associated span.
 820     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 821         self.lookup(lint, None as Option<Span>, decorate);
 822     }
 823 }
 824
 825 impl<'a> EarlyContext<'a> {
 826     pub fn new(
 827         sess: &'a Session,
 828         lint_store: &'a LintStore,
 829         krate: &'a ast::Crate,
 830         crate_attrs: &'a [ast::Attribute],
 831         buffered: LintBuffer,
 832         warn_about_weird_lints: bool,
 833     ) -> EarlyContext<'a> {
 834         EarlyContext {
 835             sess,
 836             krate,
 837             lint_store,
 838             builder: LintLevelsBuilder::new(sess, warn_about_weird_lints, lint_store, crate_attrs),
 839             buffered,
 840         }
 841     }
 842 }
 843
 844 impl LintContext for LateContext<'_> {
 845     type PassObject = LateLintPassObject;
 846
 847     /// Gets the overall compiler `Session` object.
 848     fn sess(&self) -> &Session {
 849         &self.tcx.sess
 850     }
 851
 852     fn lints(&self) -> &LintStore {
 853         &*self.lint_store
 854     }
 855
 856     fn lookup<S: Into<MultiSpan>>(
 857         &self,
 858         lint: &'static Lint,
 859         span: Option<S>,
 860         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 861     ) {
 862         let hir_id = self.last_node_with_lint_attrs;
 863
 864         match span {
 865             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 866             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 867         }
 868     }
 869 }
 870
 871 impl LintContext for EarlyContext<'_> {
 872     type PassObject = EarlyLintPassObject;
 873
 874     /// Gets the overall compiler `Session` object.
 875     fn sess(&self) -> &Session {
 876         &self.sess
 877     }
 878
 879     fn lints(&self) -> &LintStore {
 880         &*self.lint_store
 881     }
 882
 883     fn lookup<S: Into<MultiSpan>>(
 884         &self,
 885         lint: &'static Lint,
 886         span: Option<S>,
 887         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 888     ) {
 889         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 890     }
 891 }
 892
 893 impl<'tcx> LateContext<'tcx> {
 894     /// Gets the type-checking results for the current body,
 895     /// or `None` if outside a body.
 896     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 897         self.cached_typeck_results.get().or_else(|| {
 898             self.enclosing_body.map(|body| {
 899                 let typeck_results = self.tcx.typeck_body(body);
 900                 self.cached_typeck_results.set(Some(typeck_results));
 901                 typeck_results
 902             })
 903         })
 904     }
 905
 906     /// Gets the type-checking results for the current body.
 907     /// As this will ICE if called outside bodies, only call when working with
 908     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 909     #[track_caller]
 910     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 911         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 912     }
 913
 914     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 915     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 916     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 917     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 918         match *qpath {
 919             hir::QPath::Resolved(_, ref path) => path.res,
 920             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 921                 .maybe_typeck_results()
 922                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
 923                 .or_else(|| {
 924                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
 925                         Some(self.tcx.typeck(id.owner))
 926                     } else {
 927                         None
 928                     }
 929                 })
 930                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 931                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 932         }
 933     }
 934
 935     /// Check if a `DefId`'s path matches the given absolute type path usage.
 936     ///
 937     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
 938     /// inherent `impl` blocks are matched with the name of the type.
 939     ///
 940     /// Instead of using this method, it is often preferable to instead use
 941     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 942     /// as paths get invalidated if the target definition moves.
 943     ///
 944     /// # Examples
 945     ///
 946     /// ```rust,ignore (no context or def id available)
 947     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 948     ///     // The given `def_id` is that of an `Option` type
 949     /// }
 950     /// ```
 951     ///
 952     /// Used by clippy, but should be replaced by diagnostic items eventually.
 953     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 954         let names = self.get_def_path(def_id);
 955
 956         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
 957     }
 958
 959     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 960     ///
 961     /// # Examples
 962     ///
 963     /// ```rust,ignore (no context or def id available)
 964     /// let def_path = cx.get_def_path(def_id);
 965     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 966     ///     // The given `def_id` is that of an `Option` type
 967     /// }
 968     /// ```
 969     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 970         pub struct AbsolutePathPrinter<'tcx> {
 971             pub tcx: TyCtxt<'tcx>,
 972         }
 973
 974         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 975             type Error = !;
 976
 977             type Path = Vec<Symbol>;
 978             type Region = ();
 979             type Type = ();
 980             type DynExistential = ();
 981             type Const = ();
 982
 983             fn tcx(&self) -> TyCtxt<'tcx> {
 984                 self.tcx
 985             }
 986
 987             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 988                 Ok(())
 989             }
 990
 991             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 992                 Ok(())
 993             }
 994
 995             fn print_dyn_existential(
 996                 self,
 997                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
 998             ) -> Result<Self::DynExistential, Self::Error> {
 999                 Ok(())
1000             }
1001
1002             fn print_const(self, _ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
1003                 Ok(())
1004             }
1005
1006             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
1007                 Ok(vec![self.tcx.crate_name(cnum)])
1008             }
1009
1010             fn path_qualified(
1011                 self,
1012                 self_ty: Ty<'tcx>,
1013                 trait_ref: Option<ty::TraitRef<'tcx>>,
1014             ) -> Result<Self::Path, Self::Error> {
1015                 if trait_ref.is_none() {
1016                     if let ty::Adt(def, substs) = self_ty.kind() {
1017                         return self.print_def_path(def.did, substs);
1018                     }
1019                 }
1020
1021                 // This shouldn't ever be needed, but just in case:
1022                 with_no_trimmed_paths(|| {
1023                     Ok(vec![match trait_ref {
1024                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1025                         None => Symbol::intern(&format!("<{}>", self_ty)),
1026                     }])
1027                 })
1028             }
1029
1030             fn path_append_impl(
1031                 self,
1032                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1033                 _disambiguated_data: &DisambiguatedDefPathData,
1034                 self_ty: Ty<'tcx>,
1035                 trait_ref: Option<ty::TraitRef<'tcx>>,
1036             ) -> Result<Self::Path, Self::Error> {
1037                 let mut path = print_prefix(self)?;
1038
1039                 // This shouldn't ever be needed, but just in case:
1040                 path.push(match trait_ref {
1041                     Some(trait_ref) => with_no_trimmed_paths(|| {
1042                         Symbol::intern(&format!(
1043                             "<impl {} for {}>",
1044                             trait_ref.print_only_trait_path(),
1045                             self_ty
1046                         ))
1047                     }),
1048                     None => {
1049                         with_no_trimmed_paths(|| Symbol::intern(&format!("<impl {}>", self_ty)))
1050                     }
1051                 });
1052
1053                 Ok(path)
1054             }
1055
1056             fn path_append(
1057                 self,
1058                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1059                 disambiguated_data: &DisambiguatedDefPathData,
1060             ) -> Result<Self::Path, Self::Error> {
1061                 let mut path = print_prefix(self)?;
1062
1063                 // Skip `::{{constructor}}` on tuple/unit structs.
1064                 if let DefPathData::Ctor = disambiguated_data.data {
1065                     return Ok(path);
1066                 }
1067
1068                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1069                 Ok(path)
1070             }
1071
1072             fn path_generic_args(
1073                 self,
1074                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1075                 _args: &[GenericArg<'tcx>],
1076             ) -> Result<Self::Path, Self::Error> {
1077                 print_prefix(self)
1078             }
1079         }
1080
1081         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1082     }
1083 }
1084
1085 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1086     #[inline]
1087     fn data_layout(&self) -> &abi::TargetDataLayout {
1088         &self.tcx.data_layout
1089     }
1090 }
1091
1092 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1093     #[inline]
1094     fn tcx(&self) -> TyCtxt<'tcx> {
1095         self.tcx
1096     }
1097 }
1098
1099 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1100     #[inline]
1101     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1102         self.param_env
1103     }
1104 }
1105
1106 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1107     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1108
1109     #[inline]
1110     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1111         err
1112     }
1113 }
1114
1115 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1116     match lint_name.split_once("::") {
1117         Some((tool_name, lint_name)) => {
1118             let tool_name = Symbol::intern(tool_name);
1119
1120             (Some(tool_name), lint_name)
1121         }
1122         None => (None, lint_name),
1123     }
1124 }