compiler/rustc_lint/src/context.rs

   1 //! Implementation of lint checking.
   2 //!
   3 //! The lint checking is mostly consolidated into one pass which runs
   4 //! after all other analyses. Throughout compilation, lint warnings
   5 //! can be added via the `add_lint` method on the Session structure. This
   6 //! requires a span and an ID of the node that the lint is being added to. The
   7 //! lint isn't actually emitted at that time because it is unknown what the
   8 //! actual lint level at that location is.
   9 //!
  10 //! To actually emit lint warnings/errors, a separate pass is used.
  11 //! A context keeps track of the current state of all lint levels.
  12 //! Upon entering a node of the ast which can modify the lint settings, the
  13 //! previous lint state is pushed onto a stack and the ast is then recursed
  14 //! upon. As the ast is traversed, this keeps track of the current lint level
  15 //! for all lint attributes.
  16
  17 use self::TargetLint::*;
  18
  19 use crate::levels::LintLevelsBuilder;
  20 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
  21 use rustc_ast::util::unicode::TEXT_FLOW_CONTROL_CHARS;
  22 use rustc_data_structures::fx::FxHashMap;
  23 use rustc_data_structures::sync;
  24 use rustc_errors::{struct_span_err, Applicability, SuggestionStyle};
  25 use rustc_hir as hir;
  26 use rustc_hir::def::Res;
  27 use rustc_hir::def_id::{CrateNum, DefId};
  28 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  29 use rustc_middle::lint::LintDiagnosticBuilder;
  30 use rustc_middle::middle::privacy::AccessLevels;
  31 use rustc_middle::middle::stability;
  32 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  33 use rustc_middle::ty::print::with_no_trimmed_paths;
  34 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
  35 use rustc_serialize::json::Json;
  36 use rustc_session::lint::{BuiltinLintDiagnostics, ExternDepSpec};
  37 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  38 use rustc_session::Session;
  39 use rustc_span::lev_distance::find_best_match_for_name;
  40 use rustc_span::symbol::{sym, Ident, Symbol};
  41 use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};
  42 use rustc_target::abi;
  43 use tracing::debug;
  44
  45 use std::cell::Cell;
  46 use std::iter;
  47 use std::slice;
  48
  49 /// Information about the registered lints.
  50 ///
  51 /// This is basically the subset of `Context` that we can
  52 /// build early in the compile pipeline.
  53 pub struct LintStore {
  54     /// Registered lints.
  55     lints: Vec<&'static Lint>,
  56
  57     /// Constructor functions for each variety of lint pass.
  58     ///
  59     /// These should only be called once, but since we want to avoid locks or
  60     /// interior mutability, we don't enforce this (and lints should, in theory,
  61     /// be compatible with being constructed more than once, though not
  62     /// necessarily in a sane manner. This is safe though.)
  63     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  64     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  65     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  66     /// This is unique in that we construct them per-module, so not once.
  67     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  68
  69     /// Lints indexed by name.
  70     by_name: FxHashMap<String, TargetLint>,
  71
  72     /// Map of registered lint groups to what lints they expand to.
  73     lint_groups: FxHashMap<&'static str, LintGroup>,
  74 }
  75
  76 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  77 #[derive(Debug)]
  78 enum TargetLint {
  79     /// A direct lint target
  80     Id(LintId),
  81
  82     /// Temporary renaming, used for easing migration pain; see #16545
  83     Renamed(String, LintId),
  84
  85     /// Lint with this name existed previously, but has been removed/deprecated.
  86     /// The string argument is the reason for removal.
  87     Removed(String),
  88
  89     /// A lint name that should give no warnings and have no effect.
  90     ///
  91     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
  92     Ignored,
  93 }
  94
  95 pub enum FindLintError {
  96     NotFound,
  97     Removed,
  98 }
  99
 100 struct LintAlias {
 101     name: &'static str,
 102     /// Whether deprecation warnings should be suppressed for this alias.
 103     silent: bool,
 104 }
 105
 106 struct LintGroup {
 107     lint_ids: Vec<LintId>,
 108     from_plugin: bool,
 109     depr: Option<LintAlias>,
 110 }
 111
 112 pub enum CheckLintNameResult<'a> {
 113     Ok(&'a [LintId]),
 114     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 115     NoLint(Option<Symbol>),
 116     /// The lint refers to a tool that has not been registered.
 117     NoTool,
 118     /// The lint is either renamed or removed. This is the warning
 119     /// message, and an optional new name (`None` if removed).
 120     Warning(String, Option<String>),
 121     /// The lint is from a tool. If the Option is None, then either
 122     /// the lint does not exist in the tool or the code was not
 123     /// compiled with the tool and therefore the lint was never
 124     /// added to the `LintStore`. Otherwise the `LintId` will be
 125     /// returned as if it where a rustc lint.
 126     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 127 }
 128
 129 impl LintStore {
 130     pub fn new() -> LintStore {
 131         LintStore {
 132             lints: vec![],
 133             pre_expansion_passes: vec![],
 134             early_passes: vec![],
 135             late_passes: vec![],
 136             late_module_passes: vec![],
 137             by_name: Default::default(),
 138             lint_groups: Default::default(),
 139         }
 140     }
 141
 142     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 143         &self.lints
 144     }
 145
 146     pub fn get_lint_groups<'t>(
 147         &'t self,
 148     ) -> impl Iterator<Item = (&'static str, Vec<LintId>, bool)> + 't {
 149         // This function is not used in a way which observes the order of lints.
 150         #[cfg_attr(not(bootstrap), allow(rustc::potential_query_instability))]
 151         self.lint_groups
 152             .iter()
 153             .filter(|(_, LintGroup { depr, .. })| {
 154                 // Don't display deprecated lint groups.
 155                 depr.is_none()
 156             })
 157             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 158                 (*k, lint_ids.clone(), *from_plugin)
 159             })
 160     }
 161
 162     pub fn register_early_pass(
 163         &mut self,
 164         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 165     ) {
 166         self.early_passes.push(Box::new(pass));
 167     }
 168
 169     /// Used by clippy.
 170     pub fn register_pre_expansion_pass(
 171         &mut self,
 172         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 173     ) {
 174         self.pre_expansion_passes.push(Box::new(pass));
 175     }
 176
 177     pub fn register_late_pass(
 178         &mut self,
 179         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 180     ) {
 181         self.late_passes.push(Box::new(pass));
 182     }
 183
 184     pub fn register_late_mod_pass(
 185         &mut self,
 186         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 187     ) {
 188         self.late_module_passes.push(Box::new(pass));
 189     }
 190
 191     // Helper method for register_early/late_pass
 192     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 193         for lint in lints {
 194             self.lints.push(lint);
 195
 196             let id = LintId::of(lint);
 197             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 198                 bug!("duplicate specification of lint {}", lint.name_lower())
 199             }
 200
 201             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 202                 if let Some(edition) = reason.edition() {
 203                     self.lint_groups
 204                         .entry(edition.lint_name())
 205                         .or_insert(LintGroup {
 206                             lint_ids: vec![],
 207                             from_plugin: lint.is_plugin,
 208                             depr: None,
 209                         })
 210                         .lint_ids
 211                         .push(id);
 212                 } else {
 213                     // Lints belonging to the `future_incompatible` lint group are lints where a
 214                     // future version of rustc will cause existing code to stop compiling.
 215                     // Lints tied to an edition don't count because they are opt-in.
 216                     self.lint_groups
 217                         .entry("future_incompatible")
 218                         .or_insert(LintGroup {
 219                             lint_ids: vec![],
 220                             from_plugin: lint.is_plugin,
 221                             depr: None,
 222                         })
 223                         .lint_ids
 224                         .push(id);
 225                 }
 226             }
 227         }
 228     }
 229
 230     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 231         self.lint_groups.insert(
 232             alias,
 233             LintGroup {
 234                 lint_ids: vec![],
 235                 from_plugin: false,
 236                 depr: Some(LintAlias { name: lint_name, silent: true }),
 237             },
 238         );
 239     }
 240
 241     pub fn register_group(
 242         &mut self,
 243         from_plugin: bool,
 244         name: &'static str,
 245         deprecated_name: Option<&'static str>,
 246         to: Vec<LintId>,
 247     ) {
 248         let new = self
 249             .lint_groups
 250             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 251             .is_none();
 252         if let Some(deprecated) = deprecated_name {
 253             self.lint_groups.insert(
 254                 deprecated,
 255                 LintGroup {
 256                     lint_ids: vec![],
 257                     from_plugin,
 258                     depr: Some(LintAlias { name, silent: false }),
 259                 },
 260             );
 261         }
 262
 263         if !new {
 264             bug!("duplicate specification of lint group {}", name);
 265         }
 266     }
 267
 268     /// This lint should give no warning and have no effect.
 269     ///
 270     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 271     #[track_caller]
 272     pub fn register_ignored(&mut self, name: &str) {
 273         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 274             bug!("duplicate specification of lint {}", name);
 275         }
 276     }
 277
 278     /// This lint has been renamed; warn about using the new name and apply the lint.
 279     #[track_caller]
 280     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 281         let Some(&Id(target)) = self.by_name.get(new_name) else {
 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         registered_tools: &RegisteredTools,
 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(lint_name_only, tool_name, registered_tools) {
 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         lint_name: &str,
 403         tool_name: Option<Symbol>,
 404         registered_tools: &RegisteredTools,
 405     ) -> CheckLintNameResult<'_> {
 406         if let Some(tool_name) = tool_name {
 407             // FIXME: rustc and rustdoc are considered tools for lints, but not for attributes.
 408             if tool_name != sym::rustc
 409                 && tool_name != sym::rustdoc
 410                 && !registered_tools.contains(&Ident::with_dummy_span(tool_name))
 411             {
 412                 return CheckLintNameResult::NoTool;
 413             }
 414         }
 415
 416         let complete_name = if let Some(tool_name) = tool_name {
 417             format!("{}::{}", tool_name, lint_name)
 418         } else {
 419             lint_name.to_string()
 420         };
 421         // If the lint was scoped with `tool::` check if the tool lint exists
 422         if let Some(tool_name) = tool_name {
 423             match self.by_name.get(&complete_name) {
 424                 None => match self.lint_groups.get(&*complete_name) {
 425                     // If the lint isn't registered, there are two possibilities:
 426                     None => {
 427                         // 1. The tool is currently running, so this lint really doesn't exist.
 428                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 429                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 430                         let tool_prefix = format!("{}::", tool_name);
 431                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 432                             self.no_lint_suggestion(&complete_name)
 433                         } else {
 434                             // 2. The tool isn't currently running, so no lints will be registered.
 435                             // To avoid giving a false positive, ignore all unknown lints.
 436                             CheckLintNameResult::Tool(Err((None, String::new())))
 437                         };
 438                     }
 439                     Some(LintGroup { lint_ids, .. }) => {
 440                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 441                     }
 442                 },
 443                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 444                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 445                 // to treat tool_lints and rustc lints different and can use the code below.
 446                 _ => {}
 447             }
 448         }
 449         match self.by_name.get(&complete_name) {
 450             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 451                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 452                 Some(new_name.to_owned()),
 453             ),
 454             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 455                 format!("lint `{}` has been removed: {}", complete_name, reason),
 456                 None,
 457             ),
 458             None => match self.lint_groups.get(&*complete_name) {
 459                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 460                 // variant of this lint
 461                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 462                 Some(LintGroup { lint_ids, depr, .. }) => {
 463                     // Check if the lint group name is deprecated
 464                     if let Some(LintAlias { name, silent }) = depr {
 465                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 466                         return if *silent {
 467                             CheckLintNameResult::Ok(&lint_ids)
 468                         } else {
 469                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 470                         };
 471                     }
 472                     CheckLintNameResult::Ok(&lint_ids)
 473                 }
 474             },
 475             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 476             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 477         }
 478     }
 479
 480     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 481         let name_lower = lint_name.to_lowercase();
 482
 483         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 484             // First check if the lint name is (partly) in upper case instead of lower case...
 485             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 486         }
 487         // ...if not, search for lints with a similar name
 488         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 489         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 490         let names: Vec<Symbol> = groups.chain(lints).collect();
 491         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 492         CheckLintNameResult::NoLint(suggestion)
 493     }
 494
 495     fn check_tool_name_for_backwards_compat(
 496         &self,
 497         lint_name: &str,
 498         tool_name: &str,
 499     ) -> CheckLintNameResult<'_> {
 500         let complete_name = format!("{}::{}", tool_name, lint_name);
 501         match self.by_name.get(&complete_name) {
 502             None => match self.lint_groups.get(&*complete_name) {
 503                 // Now we are sure, that this lint exists nowhere
 504                 None => self.no_lint_suggestion(lint_name),
 505                 Some(LintGroup { lint_ids, depr, .. }) => {
 506                     // Reaching this would be weird, but let's cover this case anyway
 507                     if let Some(LintAlias { name, silent }) = depr {
 508                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 509                         return if *silent {
 510                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 511                         } else {
 512                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 513                         };
 514                     }
 515                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 516                 }
 517             },
 518             Some(&Id(ref id)) => {
 519                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 520             }
 521             Some(other) => {
 522                 tracing::debug!("got renamed lint {:?}", other);
 523                 CheckLintNameResult::NoLint(None)
 524             }
 525         }
 526     }
 527 }
 528
 529 /// Context for lint checking outside of type inference.
 530 pub struct LateContext<'tcx> {
 531     /// Type context we're checking in.
 532     pub tcx: TyCtxt<'tcx>,
 533
 534     /// Current body, or `None` if outside a body.
 535     pub enclosing_body: Option<hir::BodyId>,
 536
 537     /// Type-checking results for the current body. Access using the `typeck_results`
 538     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 539     // FIXME(eddyb) move all the code accessing internal fields like this,
 540     // to this module, to avoid exposing it to lint logic.
 541     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 542
 543     /// Parameter environment for the item we are in.
 544     pub param_env: ty::ParamEnv<'tcx>,
 545
 546     /// Items accessible from the crate being checked.
 547     pub access_levels: &'tcx AccessLevels,
 548
 549     /// The store of registered lints and the lint levels.
 550     pub lint_store: &'tcx LintStore,
 551
 552     pub last_node_with_lint_attrs: hir::HirId,
 553
 554     /// Generic type parameters in scope for the item we are in.
 555     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 556
 557     /// We are only looking at one module
 558     pub only_module: bool,
 559 }
 560
 561 /// Context for lint checking of the AST, after expansion, before lowering to HIR.
 562 pub struct EarlyContext<'a> {
 563     pub builder: LintLevelsBuilder<'a>,
 564     pub buffered: LintBuffer,
 565 }
 566
 567 pub trait LintPassObject: Sized {}
 568
 569 impl LintPassObject for EarlyLintPassObject {}
 570
 571 impl LintPassObject for LateLintPassObject {}
 572
 573 pub trait LintContext: Sized {
 574     type PassObject: LintPassObject;
 575
 576     fn sess(&self) -> &Session;
 577     fn lints(&self) -> &LintStore;
 578
 579     fn lookup_with_diagnostics(
 580         &self,
 581         lint: &'static Lint,
 582         span: Option<impl Into<MultiSpan>>,
 583         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 584         diagnostic: BuiltinLintDiagnostics,
 585     ) {
 586         self.lookup(lint, span, |lint| {
 587             // We first generate a blank diagnostic.
 588             let mut db = lint.build("");
 589
 590             // Now, set up surrounding context.
 591             let sess = self.sess();
 592             match diagnostic {
 593                 BuiltinLintDiagnostics::UnicodeTextFlow(span, content) => {
 594                     let spans: Vec<_> = content
 595                         .char_indices()
 596                         .filter_map(|(i, c)| {
 597                             TEXT_FLOW_CONTROL_CHARS.contains(&c).then(|| {
 598                                 let lo = span.lo() + BytePos(2 + i as u32);
 599                                 (c, span.with_lo(lo).with_hi(lo + BytePos(c.len_utf8() as u32)))
 600                             })
 601                         })
 602                         .collect();
 603                     let (an, s) = match spans.len() {
 604                         1 => ("an ", ""),
 605                         _ => ("", "s"),
 606                     };
 607                     db.span_label(span, &format!(
 608                         "this comment contains {}invisible unicode text flow control codepoint{}",
 609                         an,
 610                         s,
 611                     ));
 612                     for (c, span) in &spans {
 613                         db.span_label(*span, format!("{:?}", c));
 614                     }
 615                     db.note(
 616                         "these kind of unicode codepoints change the way text flows on \
 617                          applications that support them, but can cause confusion because they \
 618                          change the order of characters on the screen",
 619                     );
 620                     if !spans.is_empty() {
 621                         db.multipart_suggestion_with_style(
 622                             "if their presence wasn't intentional, you can remove them",
 623                             spans.into_iter().map(|(_, span)| (span, "".to_string())).collect(),
 624                             Applicability::MachineApplicable,
 625                             SuggestionStyle::HideCodeAlways,
 626                         );
 627                     }
 628                 },
 629                 BuiltinLintDiagnostics::Normal => (),
 630                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 631                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 632                         Ok(ref s) => {
 633                             // FIXME(Manishearth) ideally the emitting code
 634                             // can tell us whether or not this is global
 635                             let opt_colon =
 636                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 637
 638                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 639                         }
 640                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 641                     };
 642                     db.span_suggestion(span, "use `crate`", sugg, app);
 643                 }
 644                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 645                     db.span_label(
 646                         span,
 647                         "names from parent modules are not accessible without an explicit import",
 648                     );
 649                 }
 650                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 651                     span_def,
 652                 ) => {
 653                     db.span_note(span_def, "the macro is defined here");
 654                 }
 655                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 656                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 657                 }
 658                 BuiltinLintDiagnostics::UnusedImports(message, replaces, in_test_module) => {
 659                     if !replaces.is_empty() {
 660                         db.tool_only_multipart_suggestion(
 661                             &message,
 662                             replaces,
 663                             Applicability::MachineApplicable,
 664                         );
 665                     }
 666
 667                     if let Some(span) = in_test_module {
 668                         let def_span = self.sess().source_map().guess_head_span(span);
 669                         db.span_help(
 670                             span.shrink_to_lo().to(def_span),
 671                             "consider adding a `#[cfg(test)]` to the containing module",
 672                         );
 673                     }
 674                 }
 675                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 676                     for (span, is_imported) in spans {
 677                         let introduced = if is_imported { "imported" } else { "defined" };
 678                         db.span_label(
 679                             span,
 680                             format!("the item `{}` is already {} here", ident, introduced),
 681                         );
 682                     }
 683                 }
 684                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 685                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 686                 }
 687                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 688                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 689                     db.help("to document an item produced by a macro, \
 690                                   the macro must produce the documentation as part of its expansion");
 691                 }
 692                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 693                     db.span_suggestion(span, "remove `mut` from the parameter", ident.to_string(), Applicability::MachineApplicable);
 694                 }
 695                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 696                     db.span_label(span, "ABI should be specified here");
 697                     db.help(&format!("the default ABI is {}", default_abi.name()));
 698                 }
 699                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 700                     db.span_label(span, "the attribute is introduced here");
 701                 }
 702                 BuiltinLintDiagnostics::ExternDepSpec(krate, loc) => {
 703                     let json = match loc {
 704                         ExternDepSpec::Json(json) => {
 705                             db.help(&format!("remove unnecessary dependency `{}`", krate));
 706                             json
 707                         }
 708                         ExternDepSpec::Raw(raw) => {
 709                             db.help(&format!("remove unnecessary dependency `{}` at `{}`", krate, raw));
 710                             db.span_suggestion_with_style(
 711                                 DUMMY_SP,
 712                                 "raw extern location",
 713                                 raw.clone(),
 714                                 Applicability::Unspecified,
 715                                 SuggestionStyle::CompletelyHidden,
 716                             );
 717                             Json::String(raw)
 718                         }
 719                     };
 720                     db.tool_only_suggestion_with_metadata(
 721                         "json extern location",
 722                         Applicability::Unspecified,
 723                         json
 724                     );
 725                 }
 726                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 727                     db.note(&note);
 728                 }
 729                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 730                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 731                 }
 732                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 733                     db.span_label(span, "unknown prefix");
 734                     db.span_suggestion_verbose(
 735                         span.shrink_to_hi(),
 736                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 737                         " ".into(),
 738                         Applicability::MachineApplicable,
 739                     );
 740                 }
 741                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 742                     attr_name,
 743                     macro_name,
 744                     invoc_span
 745                 } => {
 746                     db.span_note(
 747                         invoc_span,
 748                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 749                     );
 750                 }
 751                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 752                     if is_trailing {
 753                         db.note("macro invocations at the end of a block are treated as expressions");
 754                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 755                     }
 756                 }
 757                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 758                     db.multipart_suggestion(
 759                         "wrap this expression in parentheses",
 760                         vec![(span.shrink_to_lo(), "(".to_string()),
 761                              (span.shrink_to_hi(), ")".to_string())],
 762                         Applicability::MachineApplicable
 763                     );
 764                 }
 765                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 766                     db.help(&help);
 767                     db.note("see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information");
 768                 }
 769             }
 770             // Rewrap `db`, and pass control to the user.
 771             decorate(LintDiagnosticBuilder::new(db));
 772         });
 773     }
 774
 775     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 776     // set the span in their `decorate` function (preferably using set_span).
 777     fn lookup<S: Into<MultiSpan>>(
 778         &self,
 779         lint: &'static Lint,
 780         span: Option<S>,
 781         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 782     );
 783
 784     fn struct_span_lint<S: Into<MultiSpan>>(
 785         &self,
 786         lint: &'static Lint,
 787         span: S,
 788         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 789     ) {
 790         self.lookup(lint, Some(span), decorate);
 791     }
 792     /// Emit a lint at the appropriate level, with no associated span.
 793     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 794         self.lookup(lint, None as Option<Span>, decorate);
 795     }
 796 }
 797
 798 impl<'a> EarlyContext<'a> {
 799     pub(crate) fn new(
 800         sess: &'a Session,
 801         warn_about_weird_lints: bool,
 802         lint_store: &'a LintStore,
 803         registered_tools: &'a RegisteredTools,
 804         buffered: LintBuffer,
 805     ) -> EarlyContext<'a> {
 806         EarlyContext {
 807             builder: LintLevelsBuilder::new(
 808                 sess,
 809                 warn_about_weird_lints,
 810                 lint_store,
 811                 registered_tools,
 812             ),
 813             buffered,
 814         }
 815     }
 816 }
 817
 818 impl LintContext for LateContext<'_> {
 819     type PassObject = LateLintPassObject;
 820
 821     /// Gets the overall compiler `Session` object.
 822     fn sess(&self) -> &Session {
 823         &self.tcx.sess
 824     }
 825
 826     fn lints(&self) -> &LintStore {
 827         &*self.lint_store
 828     }
 829
 830     fn lookup<S: Into<MultiSpan>>(
 831         &self,
 832         lint: &'static Lint,
 833         span: Option<S>,
 834         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 835     ) {
 836         let hir_id = self.last_node_with_lint_attrs;
 837
 838         match span {
 839             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 840             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 841         }
 842     }
 843 }
 844
 845 impl LintContext for EarlyContext<'_> {
 846     type PassObject = EarlyLintPassObject;
 847
 848     /// Gets the overall compiler `Session` object.
 849     fn sess(&self) -> &Session {
 850         &self.builder.sess()
 851     }
 852
 853     fn lints(&self) -> &LintStore {
 854         self.builder.lint_store()
 855     }
 856
 857     fn lookup<S: Into<MultiSpan>>(
 858         &self,
 859         lint: &'static Lint,
 860         span: Option<S>,
 861         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 862     ) {
 863         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 864     }
 865 }
 866
 867 impl<'tcx> LateContext<'tcx> {
 868     /// Gets the type-checking results for the current body,
 869     /// or `None` if outside a body.
 870     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 871         self.cached_typeck_results.get().or_else(|| {
 872             self.enclosing_body.map(|body| {
 873                 let typeck_results = self.tcx.typeck_body(body);
 874                 self.cached_typeck_results.set(Some(typeck_results));
 875                 typeck_results
 876             })
 877         })
 878     }
 879
 880     /// Gets the type-checking results for the current body.
 881     /// As this will ICE if called outside bodies, only call when working with
 882     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 883     #[track_caller]
 884     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 885         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 886     }
 887
 888     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 889     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 890     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 891     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 892         match *qpath {
 893             hir::QPath::Resolved(_, ref path) => path.res,
 894             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 895                 .maybe_typeck_results()
 896                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
 897                 .or_else(|| {
 898                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
 899                         Some(self.tcx.typeck(id.owner))
 900                     } else {
 901                         None
 902                     }
 903                 })
 904                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 905                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 906         }
 907     }
 908
 909     /// Check if a `DefId`'s path matches the given absolute type path usage.
 910     ///
 911     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
 912     /// inherent `impl` blocks are matched with the name of the type.
 913     ///
 914     /// Instead of using this method, it is often preferable to instead use
 915     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 916     /// as paths get invalidated if the target definition moves.
 917     ///
 918     /// # Examples
 919     ///
 920     /// ```rust,ignore (no context or def id available)
 921     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 922     ///     // The given `def_id` is that of an `Option` type
 923     /// }
 924     /// ```
 925     ///
 926     /// Used by clippy, but should be replaced by diagnostic items eventually.
 927     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 928         let names = self.get_def_path(def_id);
 929
 930         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
 931     }
 932
 933     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 934     ///
 935     /// # Examples
 936     ///
 937     /// ```rust,ignore (no context or def id available)
 938     /// let def_path = cx.get_def_path(def_id);
 939     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 940     ///     // The given `def_id` is that of an `Option` type
 941     /// }
 942     /// ```
 943     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 944         pub struct AbsolutePathPrinter<'tcx> {
 945             pub tcx: TyCtxt<'tcx>,
 946         }
 947
 948         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 949             type Error = !;
 950
 951             type Path = Vec<Symbol>;
 952             type Region = ();
 953             type Type = ();
 954             type DynExistential = ();
 955             type Const = ();
 956
 957             fn tcx(&self) -> TyCtxt<'tcx> {
 958                 self.tcx
 959             }
 960
 961             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 962                 Ok(())
 963             }
 964
 965             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 966                 Ok(())
 967             }
 968
 969             fn print_dyn_existential(
 970                 self,
 971                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
 972             ) -> Result<Self::DynExistential, Self::Error> {
 973                 Ok(())
 974             }
 975
 976             fn print_const(self, _ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 977                 Ok(())
 978             }
 979
 980             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 981                 Ok(vec![self.tcx.crate_name(cnum)])
 982             }
 983
 984             fn path_qualified(
 985                 self,
 986                 self_ty: Ty<'tcx>,
 987                 trait_ref: Option<ty::TraitRef<'tcx>>,
 988             ) -> Result<Self::Path, Self::Error> {
 989                 if trait_ref.is_none() {
 990                     if let ty::Adt(def, substs) = self_ty.kind() {
 991                         return self.print_def_path(def.did, substs);
 992                     }
 993                 }
 994
 995                 // This shouldn't ever be needed, but just in case:
 996                 with_no_trimmed_paths!({
 997                     Ok(vec![match trait_ref {
 998                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
 999                         None => Symbol::intern(&format!("<{}>", self_ty)),
1000                     }])
1001                 })
1002             }
1003
1004             fn path_append_impl(
1005                 self,
1006                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1007                 _disambiguated_data: &DisambiguatedDefPathData,
1008                 self_ty: Ty<'tcx>,
1009                 trait_ref: Option<ty::TraitRef<'tcx>>,
1010             ) -> Result<Self::Path, Self::Error> {
1011                 let mut path = print_prefix(self)?;
1012
1013                 // This shouldn't ever be needed, but just in case:
1014                 path.push(match trait_ref {
1015                     Some(trait_ref) => {
1016                         with_no_trimmed_paths!(Symbol::intern(&format!(
1017                             "<impl {} for {}>",
1018                             trait_ref.print_only_trait_path(),
1019                             self_ty
1020                         )))
1021                     }
1022                     None => {
1023                         with_no_trimmed_paths!(Symbol::intern(&format!("<impl {}>", self_ty)))
1024                     }
1025                 });
1026
1027                 Ok(path)
1028             }
1029
1030             fn path_append(
1031                 self,
1032                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1033                 disambiguated_data: &DisambiguatedDefPathData,
1034             ) -> Result<Self::Path, Self::Error> {
1035                 let mut path = print_prefix(self)?;
1036
1037                 // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
1038                 if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
1039                     return Ok(path);
1040                 }
1041
1042                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1043                 Ok(path)
1044             }
1045
1046             fn path_generic_args(
1047                 self,
1048                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1049                 _args: &[GenericArg<'tcx>],
1050             ) -> Result<Self::Path, Self::Error> {
1051                 print_prefix(self)
1052             }
1053         }
1054
1055         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1056     }
1057 }
1058
1059 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1060     #[inline]
1061     fn data_layout(&self) -> &abi::TargetDataLayout {
1062         &self.tcx.data_layout
1063     }
1064 }
1065
1066 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1067     #[inline]
1068     fn tcx(&self) -> TyCtxt<'tcx> {
1069         self.tcx
1070     }
1071 }
1072
1073 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1074     #[inline]
1075     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1076         self.param_env
1077     }
1078 }
1079
1080 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1081     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1082
1083     #[inline]
1084     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1085         err
1086     }
1087 }
1088
1089 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1090     match lint_name.split_once("::") {
1091         Some((tool_name, lint_name)) => {
1092             let tool_name = Symbol::intern(tool_name);
1093
1094             (Some(tool_name), lint_name)
1095         }
1096         None => (None, lint_name),
1097     }
1098 }