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