compiler/rustc_lint/src/context.rs

   1 //! Implementation of lint checking.
   2 //!
   3 //! The lint checking is mostly consolidated into one pass which runs
   4 //! after all other analyses. Throughout compilation, lint warnings
   5 //! can be added via the `add_lint` method on the Session structure. This
   6 //! requires a span and an ID of the node that the lint is being added to. The
   7 //! lint isn't actually emitted at that time because it is unknown what the
   8 //! actual lint level at that location is.
   9 //!
  10 //! To actually emit lint warnings/errors, a separate pass is used.
  11 //! A context keeps track of the current state of all lint levels.
  12 //! Upon entering a node of the ast which can modify the lint settings, the
  13 //! previous lint state is pushed onto a stack and the ast is then recursed
  14 //! upon. As the ast is traversed, this keeps track of the current lint level
  15 //! for all lint attributes.
  16
  17 use self::TargetLint::*;
  18
  19 use crate::levels::{is_known_lint_tool, LintLevelsBuilder};
  20 use crate::passes::{EarlyLintPassObject, LateLintPassObject};
  21 use rustc_ast as ast;
  22 use rustc_data_structures::fx::FxHashMap;
  23 use rustc_data_structures::sync;
  24 use rustc_errors::{
  25     add_elided_lifetime_in_path_suggestion, struct_span_err, Applicability, SuggestionStyle,
  26 };
  27 use rustc_hir as hir;
  28 use rustc_hir::def::Res;
  29 use rustc_hir::def_id::{CrateNum, DefId};
  30 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
  31 use rustc_middle::lint::LintDiagnosticBuilder;
  32 use rustc_middle::middle::privacy::AccessLevels;
  33 use rustc_middle::middle::stability;
  34 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
  35 use rustc_middle::ty::print::with_no_trimmed_paths;
  36 use rustc_middle::ty::{self, print::Printer, subst::GenericArg, Ty, TyCtxt};
  37 use rustc_serialize::json::Json;
  38 use rustc_session::lint::{BuiltinLintDiagnostics, ExternDepSpec};
  39 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
  40 use rustc_session::Session;
  41 use rustc_session::SessionLintStore;
  42 use rustc_span::lev_distance::find_best_match_for_name;
  43 use rustc_span::{symbol::Symbol, MultiSpan, Span, DUMMY_SP};
  44 use rustc_target::abi;
  45 use tracing::debug;
  46
  47 use std::cell::Cell;
  48 use std::iter;
  49 use std::slice;
  50
  51 /// Information about the registered lints.
  52 ///
  53 /// This is basically the subset of `Context` that we can
  54 /// build early in the compile pipeline.
  55 pub struct LintStore {
  56     /// Registered lints.
  57     lints: Vec<&'static Lint>,
  58
  59     /// Constructor functions for each variety of lint pass.
  60     ///
  61     /// These should only be called once, but since we want to avoid locks or
  62     /// interior mutability, we don't enforce this (and lints should, in theory,
  63     /// be compatible with being constructed more than once, though not
  64     /// necessarily in a sane manner. This is safe though.)
  65     pub pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  66     pub early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
  67     pub late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  68     /// This is unique in that we construct them per-module, so not once.
  69     pub late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
  70
  71     /// Lints indexed by name.
  72     by_name: FxHashMap<String, TargetLint>,
  73
  74     /// Map of registered lint groups to what lints they expand to.
  75     lint_groups: FxHashMap<&'static str, LintGroup>,
  76 }
  77
  78 impl SessionLintStore for LintStore {
  79     fn name_to_lint(&self, lint_name: &str) -> LintId {
  80         let lints = self
  81             .find_lints(lint_name)
  82             .unwrap_or_else(|_| panic!("Failed to find lint with name `{}`", lint_name));
  83
  84         if let &[lint] = lints.as_slice() {
  85             return lint;
  86         } else {
  87             panic!("Found mutliple lints with name `{}`: {:?}", lint_name, lints);
  88         }
  89     }
  90 }
  91
  92 /// The target of the `by_name` map, which accounts for renaming/deprecation.
  93 #[derive(Debug)]
  94 enum TargetLint {
  95     /// A direct lint target
  96     Id(LintId),
  97
  98     /// Temporary renaming, used for easing migration pain; see #16545
  99     Renamed(String, LintId),
 100
 101     /// Lint with this name existed previously, but has been removed/deprecated.
 102     /// The string argument is the reason for removal.
 103     Removed(String),
 104
 105     /// A lint name that should give no warnings and have no effect.
 106     ///
 107     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 108     Ignored,
 109 }
 110
 111 pub enum FindLintError {
 112     NotFound,
 113     Removed,
 114 }
 115
 116 struct LintAlias {
 117     name: &'static str,
 118     /// Whether deprecation warnings should be suppressed for this alias.
 119     silent: bool,
 120 }
 121
 122 struct LintGroup {
 123     lint_ids: Vec<LintId>,
 124     from_plugin: bool,
 125     depr: Option<LintAlias>,
 126 }
 127
 128 pub enum CheckLintNameResult<'a> {
 129     Ok(&'a [LintId]),
 130     /// Lint doesn't exist. Potentially contains a suggestion for a correct lint name.
 131     NoLint(Option<Symbol>),
 132     /// The lint refers to a tool that has not been registered.
 133     NoTool,
 134     /// The lint is either renamed or removed. This is the warning
 135     /// message, and an optional new name (`None` if removed).
 136     Warning(String, Option<String>),
 137     /// The lint is from a tool. If the Option is None, then either
 138     /// the lint does not exist in the tool or the code was not
 139     /// compiled with the tool and therefore the lint was never
 140     /// added to the `LintStore`. Otherwise the `LintId` will be
 141     /// returned as if it where a rustc lint.
 142     Tool(Result<&'a [LintId], (Option<&'a [LintId]>, String)>),
 143 }
 144
 145 impl LintStore {
 146     pub fn new() -> LintStore {
 147         LintStore {
 148             lints: vec![],
 149             pre_expansion_passes: vec![],
 150             early_passes: vec![],
 151             late_passes: vec![],
 152             late_module_passes: vec![],
 153             by_name: Default::default(),
 154             lint_groups: Default::default(),
 155         }
 156     }
 157
 158     pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
 159         &self.lints
 160     }
 161
 162     pub fn get_lint_groups<'t>(&'t self) -> Vec<(&'static str, Vec<LintId>, bool)> {
 163         self.lint_groups
 164             .iter()
 165             .filter(|(_, LintGroup { depr, .. })| {
 166                 // Don't display deprecated lint groups.
 167                 depr.is_none()
 168             })
 169             .map(|(k, LintGroup { lint_ids, from_plugin, .. })| {
 170                 (*k, lint_ids.clone(), *from_plugin)
 171             })
 172             .collect()
 173     }
 174
 175     pub fn register_early_pass(
 176         &mut self,
 177         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 178     ) {
 179         self.early_passes.push(Box::new(pass));
 180     }
 181
 182     /// Used by clippy.
 183     pub fn register_pre_expansion_pass(
 184         &mut self,
 185         pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
 186     ) {
 187         self.pre_expansion_passes.push(Box::new(pass));
 188     }
 189
 190     pub fn register_late_pass(
 191         &mut self,
 192         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 193     ) {
 194         self.late_passes.push(Box::new(pass));
 195     }
 196
 197     pub fn register_late_mod_pass(
 198         &mut self,
 199         pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
 200     ) {
 201         self.late_module_passes.push(Box::new(pass));
 202     }
 203
 204     // Helper method for register_early/late_pass
 205     pub fn register_lints(&mut self, lints: &[&'static Lint]) {
 206         for lint in lints {
 207             self.lints.push(lint);
 208
 209             let id = LintId::of(lint);
 210             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
 211                 bug!("duplicate specification of lint {}", lint.name_lower())
 212             }
 213
 214             if let Some(FutureIncompatibleInfo { reason, .. }) = lint.future_incompatible {
 215                 if let Some(edition) = reason.edition() {
 216                     self.lint_groups
 217                         .entry(edition.lint_name())
 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                 } else {
 226                     // Lints belonging to the `future_incompatible` lint group are lints where a
 227                     // future version of rustc will cause existing code to stop compiling.
 228                     // Lints tied to an edition don't count because they are opt-in.
 229                     self.lint_groups
 230                         .entry("future_incompatible")
 231                         .or_insert(LintGroup {
 232                             lint_ids: vec![],
 233                             from_plugin: lint.is_plugin,
 234                             depr: None,
 235                         })
 236                         .lint_ids
 237                         .push(id);
 238                 }
 239             }
 240         }
 241     }
 242
 243     pub fn register_group_alias(&mut self, lint_name: &'static str, alias: &'static str) {
 244         self.lint_groups.insert(
 245             alias,
 246             LintGroup {
 247                 lint_ids: vec![],
 248                 from_plugin: false,
 249                 depr: Some(LintAlias { name: lint_name, silent: true }),
 250             },
 251         );
 252     }
 253
 254     pub fn register_group(
 255         &mut self,
 256         from_plugin: bool,
 257         name: &'static str,
 258         deprecated_name: Option<&'static str>,
 259         to: Vec<LintId>,
 260     ) {
 261         let new = self
 262             .lint_groups
 263             .insert(name, LintGroup { lint_ids: to, from_plugin, depr: None })
 264             .is_none();
 265         if let Some(deprecated) = deprecated_name {
 266             self.lint_groups.insert(
 267                 deprecated,
 268                 LintGroup {
 269                     lint_ids: vec![],
 270                     from_plugin,
 271                     depr: Some(LintAlias { name, silent: false }),
 272                 },
 273             );
 274         }
 275
 276         if !new {
 277             bug!("duplicate specification of lint group {}", name);
 278         }
 279     }
 280
 281     /// This lint should give no warning and have no effect.
 282     ///
 283     /// This is used by rustc to avoid warning about old rustdoc lints before rustdoc registers them as tool lints.
 284     #[track_caller]
 285     pub fn register_ignored(&mut self, name: &str) {
 286         if self.by_name.insert(name.to_string(), Ignored).is_some() {
 287             bug!("duplicate specification of lint {}", name);
 288         }
 289     }
 290
 291     /// This lint has been renamed; warn about using the new name and apply the lint.
 292     #[track_caller]
 293     pub fn register_renamed(&mut self, old_name: &str, new_name: &str) {
 294         let target = match self.by_name.get(new_name) {
 295             Some(&Id(lint_id)) => lint_id,
 296             _ => bug!("invalid lint renaming of {} to {}", old_name, new_name),
 297         };
 298         self.by_name.insert(old_name.to_string(), Renamed(new_name.to_string(), target));
 299     }
 300
 301     pub fn register_removed(&mut self, name: &str, reason: &str) {
 302         self.by_name.insert(name.into(), Removed(reason.into()));
 303     }
 304
 305     pub fn find_lints(&self, mut lint_name: &str) -> Result<Vec<LintId>, FindLintError> {
 306         match self.by_name.get(lint_name) {
 307             Some(&Id(lint_id)) => Ok(vec![lint_id]),
 308             Some(&Renamed(_, lint_id)) => Ok(vec![lint_id]),
 309             Some(&Removed(_)) => Err(FindLintError::Removed),
 310             Some(&Ignored) => Ok(vec![]),
 311             None => loop {
 312                 return match self.lint_groups.get(lint_name) {
 313                     Some(LintGroup { lint_ids, depr, .. }) => {
 314                         if let Some(LintAlias { name, .. }) = depr {
 315                             lint_name = name;
 316                             continue;
 317                         }
 318                         Ok(lint_ids.clone())
 319                     }
 320                     None => Err(FindLintError::Removed),
 321                 };
 322             },
 323         }
 324     }
 325
 326     /// Checks the validity of lint names derived from the command line.
 327     pub fn check_lint_name_cmdline(
 328         &self,
 329         sess: &Session,
 330         lint_name: &str,
 331         level: Level,
 332         crate_attrs: &[ast::Attribute],
 333     ) {
 334         let (tool_name, lint_name_only) = parse_lint_and_tool_name(lint_name);
 335         if lint_name_only == crate::WARNINGS.name_lower() && level == Level::ForceWarn {
 336             return struct_span_err!(
 337                 sess,
 338                 DUMMY_SP,
 339                 E0602,
 340                 "`{}` lint group is not supported with ´--force-warn´",
 341                 crate::WARNINGS.name_lower()
 342             )
 343             .emit();
 344         }
 345         let db = match self.check_lint_name(sess, lint_name_only, tool_name, crate_attrs) {
 346             CheckLintNameResult::Ok(_) => None,
 347             CheckLintNameResult::Warning(ref msg, _) => Some(sess.struct_warn(msg)),
 348             CheckLintNameResult::NoLint(suggestion) => {
 349                 let mut err =
 350                     struct_span_err!(sess, DUMMY_SP, E0602, "unknown lint: `{}`", lint_name);
 351
 352                 if let Some(suggestion) = suggestion {
 353                     err.help(&format!("did you mean: `{}`", suggestion));
 354                 }
 355
 356                 Some(err)
 357             }
 358             CheckLintNameResult::Tool(result) => match result {
 359                 Err((Some(_), new_name)) => Some(sess.struct_warn(&format!(
 360                     "lint name `{}` is deprecated \
 361                      and does not have an effect anymore. \
 362                      Use: {}",
 363                     lint_name, new_name
 364                 ))),
 365                 _ => None,
 366             },
 367             CheckLintNameResult::NoTool => Some(struct_span_err!(
 368                 sess,
 369                 DUMMY_SP,
 370                 E0602,
 371                 "unknown lint tool: `{}`",
 372                 tool_name.unwrap()
 373             )),
 374         };
 375
 376         if let Some(mut db) = db {
 377             let msg = format!(
 378                 "requested on the command line with `{} {}`",
 379                 match level {
 380                     Level::Allow => "-A",
 381                     Level::Warn => "-W",
 382                     Level::ForceWarn => "--force-warn",
 383                     Level::Deny => "-D",
 384                     Level::Forbid => "-F",
 385                 },
 386                 lint_name
 387             );
 388             db.note(&msg);
 389             db.emit();
 390         }
 391     }
 392
 393     /// True if this symbol represents a lint group name.
 394     pub fn is_lint_group(&self, lint_name: Symbol) -> bool {
 395         debug!(
 396             "is_lint_group(lint_name={:?}, lint_groups={:?})",
 397             lint_name,
 398             self.lint_groups.keys().collect::<Vec<_>>()
 399         );
 400         let lint_name_str = &*lint_name.as_str();
 401         self.lint_groups.contains_key(&lint_name_str) || {
 402             let warnings_name_str = crate::WARNINGS.name_lower();
 403             lint_name_str == &*warnings_name_str
 404         }
 405     }
 406
 407     /// Checks the name of a lint for its existence, and whether it was
 408     /// renamed or removed. Generates a DiagnosticBuilder containing a
 409     /// warning for renamed and removed lints. This is over both lint
 410     /// names from attributes and those passed on the command line. Since
 411     /// it emits non-fatal warnings and there are *two* lint passes that
 412     /// inspect attributes, this is only run from the late pass to avoid
 413     /// printing duplicate warnings.
 414     pub fn check_lint_name(
 415         &self,
 416         sess: &Session,
 417         lint_name: &str,
 418         tool_name: Option<Symbol>,
 419         crate_attrs: &[ast::Attribute],
 420     ) -> CheckLintNameResult<'_> {
 421         if let Some(tool_name) = tool_name {
 422             if !is_known_lint_tool(tool_name, sess, crate_attrs) {
 423                 return CheckLintNameResult::NoTool;
 424             }
 425         }
 426
 427         let complete_name = if let Some(tool_name) = tool_name {
 428             format!("{}::{}", tool_name, lint_name)
 429         } else {
 430             lint_name.to_string()
 431         };
 432         // If the lint was scoped with `tool::` check if the tool lint exists
 433         if let Some(tool_name) = tool_name {
 434             match self.by_name.get(&complete_name) {
 435                 None => match self.lint_groups.get(&*complete_name) {
 436                     // If the lint isn't registered, there are two possibilities:
 437                     None => {
 438                         // 1. The tool is currently running, so this lint really doesn't exist.
 439                         // FIXME: should this handle tools that never register a lint, like rustfmt?
 440                         tracing::debug!("lints={:?}", self.by_name.keys().collect::<Vec<_>>());
 441                         let tool_prefix = format!("{}::", tool_name);
 442                         return if self.by_name.keys().any(|lint| lint.starts_with(&tool_prefix)) {
 443                             self.no_lint_suggestion(&complete_name)
 444                         } else {
 445                             // 2. The tool isn't currently running, so no lints will be registered.
 446                             // To avoid giving a false positive, ignore all unknown lints.
 447                             CheckLintNameResult::Tool(Err((None, String::new())))
 448                         };
 449                     }
 450                     Some(LintGroup { lint_ids, .. }) => {
 451                         return CheckLintNameResult::Tool(Ok(&lint_ids));
 452                     }
 453                 },
 454                 Some(&Id(ref id)) => return CheckLintNameResult::Tool(Ok(slice::from_ref(id))),
 455                 // If the lint was registered as removed or renamed by the lint tool, we don't need
 456                 // to treat tool_lints and rustc lints different and can use the code below.
 457                 _ => {}
 458             }
 459         }
 460         match self.by_name.get(&complete_name) {
 461             Some(&Renamed(ref new_name, _)) => CheckLintNameResult::Warning(
 462                 format!("lint `{}` has been renamed to `{}`", complete_name, new_name),
 463                 Some(new_name.to_owned()),
 464             ),
 465             Some(&Removed(ref reason)) => CheckLintNameResult::Warning(
 466                 format!("lint `{}` has been removed: {}", complete_name, reason),
 467                 None,
 468             ),
 469             None => match self.lint_groups.get(&*complete_name) {
 470                 // If neither the lint, nor the lint group exists check if there is a `clippy::`
 471                 // variant of this lint
 472                 None => self.check_tool_name_for_backwards_compat(&complete_name, "clippy"),
 473                 Some(LintGroup { lint_ids, depr, .. }) => {
 474                     // Check if the lint group name is deprecated
 475                     if let Some(LintAlias { name, silent }) = depr {
 476                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 477                         return if *silent {
 478                             CheckLintNameResult::Ok(&lint_ids)
 479                         } else {
 480                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 481                         };
 482                     }
 483                     CheckLintNameResult::Ok(&lint_ids)
 484                 }
 485             },
 486             Some(&Id(ref id)) => CheckLintNameResult::Ok(slice::from_ref(id)),
 487             Some(&Ignored) => CheckLintNameResult::Ok(&[]),
 488         }
 489     }
 490
 491     fn no_lint_suggestion(&self, lint_name: &str) -> CheckLintNameResult<'_> {
 492         let name_lower = lint_name.to_lowercase();
 493
 494         if lint_name.chars().any(char::is_uppercase) && self.find_lints(&name_lower).is_ok() {
 495             // First check if the lint name is (partly) in upper case instead of lower case...
 496             return CheckLintNameResult::NoLint(Some(Symbol::intern(&name_lower)));
 497         }
 498         // ...if not, search for lints with a similar name
 499         let groups = self.lint_groups.keys().copied().map(Symbol::intern);
 500         let lints = self.lints.iter().map(|l| Symbol::intern(&l.name_lower()));
 501         let names: Vec<Symbol> = groups.chain(lints).collect();
 502         let suggestion = find_best_match_for_name(&names, Symbol::intern(&name_lower), None);
 503         CheckLintNameResult::NoLint(suggestion)
 504     }
 505
 506     fn check_tool_name_for_backwards_compat(
 507         &self,
 508         lint_name: &str,
 509         tool_name: &str,
 510     ) -> CheckLintNameResult<'_> {
 511         let complete_name = format!("{}::{}", tool_name, lint_name);
 512         match self.by_name.get(&complete_name) {
 513             None => match self.lint_groups.get(&*complete_name) {
 514                 // Now we are sure, that this lint exists nowhere
 515                 None => self.no_lint_suggestion(lint_name),
 516                 Some(LintGroup { lint_ids, depr, .. }) => {
 517                     // Reaching this would be weird, but let's cover this case anyway
 518                     if let Some(LintAlias { name, silent }) = depr {
 519                         let LintGroup { lint_ids, .. } = self.lint_groups.get(name).unwrap();
 520                         return if *silent {
 521                             CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 522                         } else {
 523                             CheckLintNameResult::Tool(Err((Some(&lint_ids), (*name).to_string())))
 524                         };
 525                     }
 526                     CheckLintNameResult::Tool(Err((Some(&lint_ids), complete_name)))
 527                 }
 528             },
 529             Some(&Id(ref id)) => {
 530                 CheckLintNameResult::Tool(Err((Some(slice::from_ref(id)), complete_name)))
 531             }
 532             Some(other) => {
 533                 tracing::debug!("got renamed lint {:?}", other);
 534                 CheckLintNameResult::NoLint(None)
 535             }
 536         }
 537     }
 538 }
 539
 540 /// Context for lint checking after type checking.
 541 pub struct LateContext<'tcx> {
 542     /// Type context we're checking in.
 543     pub tcx: TyCtxt<'tcx>,
 544
 545     /// Current body, or `None` if outside a body.
 546     pub enclosing_body: Option<hir::BodyId>,
 547
 548     /// Type-checking results for the current body. Access using the `typeck_results`
 549     /// and `maybe_typeck_results` methods, which handle querying the typeck results on demand.
 550     // FIXME(eddyb) move all the code accessing internal fields like this,
 551     // to this module, to avoid exposing it to lint logic.
 552     pub(super) cached_typeck_results: Cell<Option<&'tcx ty::TypeckResults<'tcx>>>,
 553
 554     /// Parameter environment for the item we are in.
 555     pub param_env: ty::ParamEnv<'tcx>,
 556
 557     /// Items accessible from the crate being checked.
 558     pub access_levels: &'tcx AccessLevels,
 559
 560     /// The store of registered lints and the lint levels.
 561     pub lint_store: &'tcx LintStore,
 562
 563     pub last_node_with_lint_attrs: hir::HirId,
 564
 565     /// Generic type parameters in scope for the item we are in.
 566     pub generics: Option<&'tcx hir::Generics<'tcx>>,
 567
 568     /// We are only looking at one module
 569     pub only_module: bool,
 570 }
 571
 572 /// Context for lint checking of the AST, after expansion, before lowering to
 573 /// HIR.
 574 pub struct EarlyContext<'a> {
 575     /// Type context we're checking in.
 576     pub sess: &'a Session,
 577
 578     /// The crate being checked.
 579     pub krate: &'a ast::Crate,
 580
 581     pub builder: LintLevelsBuilder<'a>,
 582
 583     /// The store of registered lints and the lint levels.
 584     pub lint_store: &'a LintStore,
 585
 586     pub buffered: LintBuffer,
 587 }
 588
 589 pub trait LintPassObject: Sized {}
 590
 591 impl LintPassObject for EarlyLintPassObject {}
 592
 593 impl LintPassObject for LateLintPassObject {}
 594
 595 pub trait LintContext: Sized {
 596     type PassObject: LintPassObject;
 597
 598     fn sess(&self) -> &Session;
 599     fn lints(&self) -> &LintStore;
 600
 601     fn lookup_with_diagnostics(
 602         &self,
 603         lint: &'static Lint,
 604         span: Option<impl Into<MultiSpan>>,
 605         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 606         diagnostic: BuiltinLintDiagnostics,
 607     ) {
 608         self.lookup(lint, span, |lint| {
 609             // We first generate a blank diagnostic.
 610             let mut db = lint.build("");
 611
 612             // Now, set up surrounding context.
 613             let sess = self.sess();
 614             match diagnostic {
 615                 BuiltinLintDiagnostics::Normal => (),
 616                 BuiltinLintDiagnostics::BareTraitObject(span, is_global) => {
 617                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 618                         Ok(s) if is_global => {
 619                             (format!("dyn ({})", s), Applicability::MachineApplicable)
 620                         }
 621                         Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
 622                         Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
 623                     };
 624                     db.span_suggestion(span, "use `dyn`", sugg, app);
 625                 }
 626                 BuiltinLintDiagnostics::AbsPathWithModule(span) => {
 627                     let (sugg, app) = match sess.source_map().span_to_snippet(span) {
 628                         Ok(ref s) => {
 629                             // FIXME(Manishearth) ideally the emitting code
 630                             // can tell us whether or not this is global
 631                             let opt_colon =
 632                                 if s.trim_start().starts_with("::") { "" } else { "::" };
 633
 634                             (format!("crate{}{}", opt_colon, s), Applicability::MachineApplicable)
 635                         }
 636                         Err(_) => ("crate::<path>".to_string(), Applicability::HasPlaceholders),
 637                     };
 638                     db.span_suggestion(span, "use `crate`", sugg, app);
 639                 }
 640                 BuiltinLintDiagnostics::ProcMacroDeriveResolutionFallback(span) => {
 641                     db.span_label(
 642                         span,
 643                         "names from parent modules are not accessible without an explicit import",
 644                     );
 645                 }
 646                 BuiltinLintDiagnostics::MacroExpandedMacroExportsAccessedByAbsolutePaths(
 647                     span_def,
 648                 ) => {
 649                     db.span_note(span_def, "the macro is defined here");
 650                 }
 651                 BuiltinLintDiagnostics::ElidedLifetimesInPaths(
 652                     n,
 653                     path_span,
 654                     incl_angl_brckt,
 655                     insertion_span,
 656                     anon_lts,
 657                 ) => {
 658                     add_elided_lifetime_in_path_suggestion(
 659                         sess.source_map(),
 660                         &mut db,
 661                         n,
 662                         path_span,
 663                         incl_angl_brckt,
 664                         insertion_span,
 665                         anon_lts,
 666                     );
 667                 }
 668                 BuiltinLintDiagnostics::UnknownCrateTypes(span, note, sugg) => {
 669                     db.span_suggestion(span, &note, sugg, Applicability::MaybeIncorrect);
 670                 }
 671                 BuiltinLintDiagnostics::UnusedImports(message, replaces) => {
 672                     if !replaces.is_empty() {
 673                         db.tool_only_multipart_suggestion(
 674                             &message,
 675                             replaces,
 676                             Applicability::MachineApplicable,
 677                         );
 678                     }
 679                 }
 680                 BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
 681                     for (span, is_imported) in spans {
 682                         let introduced = if is_imported { "imported" } else { "defined" };
 683                         db.span_label(
 684                             span,
 685                             format!("the item `{}` is already {} here", ident, introduced),
 686                         );
 687                     }
 688                 }
 689                 BuiltinLintDiagnostics::DeprecatedMacro(suggestion, span) => {
 690                     stability::deprecation_suggestion(&mut db, "macro", suggestion, span)
 691                 }
 692                 BuiltinLintDiagnostics::UnusedDocComment(span) => {
 693                     db.span_label(span, "rustdoc does not generate documentation for macro invocations");
 694                     db.help("to document an item produced by a macro, \
 695                                   the macro must produce the documentation as part of its expansion");
 696                 }
 697                 BuiltinLintDiagnostics::PatternsInFnsWithoutBody(span, ident) => {
 698                     db.span_suggestion(span, "remove `mut` from the parameter", ident.to_string(), Applicability::MachineApplicable);
 699                 }
 700                 BuiltinLintDiagnostics::MissingAbi(span, default_abi) => {
 701                     db.span_label(span, "ABI should be specified here");
 702                     db.help(&format!("the default ABI is {}", default_abi.name()));
 703                 }
 704                 BuiltinLintDiagnostics::LegacyDeriveHelpers(span) => {
 705                     db.span_label(span, "the attribute is introduced here");
 706                 }
 707                 BuiltinLintDiagnostics::ExternDepSpec(krate, loc) => {
 708                     let json = match loc {
 709                         ExternDepSpec::Json(json) => {
 710                             db.help(&format!("remove unnecessary dependency `{}`", krate));
 711                             json
 712                         }
 713                         ExternDepSpec::Raw(raw) => {
 714                             db.help(&format!("remove unnecessary dependency `{}` at `{}`", krate, raw));
 715                             db.span_suggestion_with_style(
 716                                 DUMMY_SP,
 717                                 "raw extern location",
 718                                 raw.clone(),
 719                                 Applicability::Unspecified,
 720                                 SuggestionStyle::CompletelyHidden,
 721                             );
 722                             Json::String(raw)
 723                         }
 724                     };
 725                     db.tool_only_suggestion_with_metadata(
 726                         "json extern location",
 727                         Applicability::Unspecified,
 728                         json
 729                     );
 730                 }
 731                 BuiltinLintDiagnostics::ProcMacroBackCompat(note) => {
 732                     db.note(&note);
 733                 }
 734                 BuiltinLintDiagnostics::OrPatternsBackCompat(span,suggestion) => {
 735                     db.span_suggestion(span, "use pat_param to preserve semantics", suggestion, Applicability::MachineApplicable);
 736                 }
 737                 BuiltinLintDiagnostics::ReservedPrefix(span) => {
 738                     db.span_label(span, "unknown prefix");
 739                     db.span_suggestion_verbose(
 740                         span.shrink_to_hi(),
 741                         "insert whitespace here to avoid this being parsed as a prefix in Rust 2021",
 742                         " ".into(),
 743                         Applicability::MachineApplicable,
 744                     );
 745                 }
 746                 BuiltinLintDiagnostics::UnusedBuiltinAttribute {
 747                     attr_name,
 748                     macro_name,
 749                     invoc_span
 750                 } => {
 751                     db.span_note(
 752                         invoc_span,
 753                         &format!("the built-in attribute `{attr_name}` will be ignored, since it's applied to the macro invocation `{macro_name}`")
 754                     );
 755                 }
 756                 BuiltinLintDiagnostics::TrailingMacro(is_trailing, name) => {
 757                     if is_trailing {
 758                         db.note("macro invocations at the end of a block are treated as expressions");
 759                         db.note(&format!("to ignore the value produced by the macro, add a semicolon after the invocation of `{name}`"));
 760                     }
 761                 }
 762                 BuiltinLintDiagnostics::BreakWithLabelAndLoop(span) => {
 763                     db.multipart_suggestion(
 764                         "wrap this expression in parentheses",
 765                         vec![(span.shrink_to_lo(), "(".to_string()),
 766                              (span.shrink_to_hi(), ")".to_string())],
 767                         Applicability::MachineApplicable
 768                     );
 769                 }
 770                 BuiltinLintDiagnostics::NamedAsmLabel(help) => {
 771                     db.help(&help);
 772                     db.note("see the asm section of the unstable book <https://doc.rust-lang.org/nightly/unstable-book/library-features/asm.html#labels> for more information");
 773                 }
 774             }
 775             // Rewrap `db`, and pass control to the user.
 776             decorate(LintDiagnosticBuilder::new(db));
 777         });
 778     }
 779
 780     // FIXME: These methods should not take an Into<MultiSpan> -- instead, callers should need to
 781     // set the span in their `decorate` function (preferably using set_span).
 782     fn lookup<S: Into<MultiSpan>>(
 783         &self,
 784         lint: &'static Lint,
 785         span: Option<S>,
 786         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 787     );
 788
 789     fn struct_span_lint<S: Into<MultiSpan>>(
 790         &self,
 791         lint: &'static Lint,
 792         span: S,
 793         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 794     ) {
 795         self.lookup(lint, Some(span), decorate);
 796     }
 797     /// Emit a lint at the appropriate level, with no associated span.
 798     fn lint(&self, lint: &'static Lint, decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>)) {
 799         self.lookup(lint, None as Option<Span>, decorate);
 800     }
 801 }
 802
 803 impl<'a> EarlyContext<'a> {
 804     pub fn new(
 805         sess: &'a Session,
 806         lint_store: &'a LintStore,
 807         krate: &'a ast::Crate,
 808         buffered: LintBuffer,
 809         warn_about_weird_lints: bool,
 810     ) -> EarlyContext<'a> {
 811         EarlyContext {
 812             sess,
 813             krate,
 814             lint_store,
 815             builder: LintLevelsBuilder::new(sess, warn_about_weird_lints, lint_store, &krate.attrs),
 816             buffered,
 817         }
 818     }
 819 }
 820
 821 impl LintContext for LateContext<'_> {
 822     type PassObject = LateLintPassObject;
 823
 824     /// Gets the overall compiler `Session` object.
 825     fn sess(&self) -> &Session {
 826         &self.tcx.sess
 827     }
 828
 829     fn lints(&self) -> &LintStore {
 830         &*self.lint_store
 831     }
 832
 833     fn lookup<S: Into<MultiSpan>>(
 834         &self,
 835         lint: &'static Lint,
 836         span: Option<S>,
 837         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 838     ) {
 839         let hir_id = self.last_node_with_lint_attrs;
 840
 841         match span {
 842             Some(s) => self.tcx.struct_span_lint_hir(lint, hir_id, s, decorate),
 843             None => self.tcx.struct_lint_node(lint, hir_id, decorate),
 844         }
 845     }
 846 }
 847
 848 impl LintContext for EarlyContext<'_> {
 849     type PassObject = EarlyLintPassObject;
 850
 851     /// Gets the overall compiler `Session` object.
 852     fn sess(&self) -> &Session {
 853         &self.sess
 854     }
 855
 856     fn lints(&self) -> &LintStore {
 857         &*self.lint_store
 858     }
 859
 860     fn lookup<S: Into<MultiSpan>>(
 861         &self,
 862         lint: &'static Lint,
 863         span: Option<S>,
 864         decorate: impl for<'a> FnOnce(LintDiagnosticBuilder<'a>),
 865     ) {
 866         self.builder.struct_lint(lint, span.map(|s| s.into()), decorate)
 867     }
 868 }
 869
 870 impl<'tcx> LateContext<'tcx> {
 871     /// Gets the type-checking results for the current body,
 872     /// or `None` if outside a body.
 873     pub fn maybe_typeck_results(&self) -> Option<&'tcx ty::TypeckResults<'tcx>> {
 874         self.cached_typeck_results.get().or_else(|| {
 875             self.enclosing_body.map(|body| {
 876                 let typeck_results = self.tcx.typeck_body(body);
 877                 self.cached_typeck_results.set(Some(typeck_results));
 878                 typeck_results
 879             })
 880         })
 881     }
 882
 883     /// Gets the type-checking results for the current body.
 884     /// As this will ICE if called outside bodies, only call when working with
 885     /// `Expr` or `Pat` nodes (they are guaranteed to be found only in bodies).
 886     #[track_caller]
 887     pub fn typeck_results(&self) -> &'tcx ty::TypeckResults<'tcx> {
 888         self.maybe_typeck_results().expect("`LateContext::typeck_results` called outside of body")
 889     }
 890
 891     /// Returns the final resolution of a `QPath`, or `Res::Err` if unavailable.
 892     /// Unlike `.typeck_results().qpath_res(qpath, id)`, this can be used even outside
 893     /// bodies (e.g. for paths in `hir::Ty`), without any risk of ICE-ing.
 894     pub fn qpath_res(&self, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
 895         match *qpath {
 896             hir::QPath::Resolved(_, ref path) => path.res,
 897             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
 898                 .maybe_typeck_results()
 899                 .filter(|typeck_results| typeck_results.hir_owner == id.owner)
 900                 .or_else(|| {
 901                     if self.tcx.has_typeck_results(id.owner.to_def_id()) {
 902                         Some(self.tcx.typeck(id.owner))
 903                     } else {
 904                         None
 905                     }
 906                 })
 907                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
 908                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
 909         }
 910     }
 911
 912     /// Check if a `DefId`'s path matches the given absolute type path usage.
 913     ///
 914     /// Anonymous scopes such as `extern` imports are matched with `kw::Empty`;
 915     /// inherent `impl` blocks are matched with the name of the type.
 916     ///
 917     /// Instead of using this method, it is often preferable to instead use
 918     /// `rustc_diagnostic_item` or a `lang_item`. This is less prone to errors
 919     /// as paths get invalidated if the target definition moves.
 920     ///
 921     /// # Examples
 922     ///
 923     /// ```rust,ignore (no context or def id available)
 924     /// if cx.match_def_path(def_id, &[sym::core, sym::option, sym::Option]) {
 925     ///     // The given `def_id` is that of an `Option` type
 926     /// }
 927     /// ```
 928     ///
 929     /// Used by clippy, but should be replaced by diagnostic items eventually.
 930     pub fn match_def_path(&self, def_id: DefId, path: &[Symbol]) -> bool {
 931         let names = self.get_def_path(def_id);
 932
 933         names.len() == path.len() && iter::zip(names, path).all(|(a, &b)| a == b)
 934     }
 935
 936     /// Gets the absolute path of `def_id` as a vector of `Symbol`.
 937     ///
 938     /// # Examples
 939     ///
 940     /// ```rust,ignore (no context or def id available)
 941     /// let def_path = cx.get_def_path(def_id);
 942     /// if let &[sym::core, sym::option, sym::Option] = &def_path[..] {
 943     ///     // The given `def_id` is that of an `Option` type
 944     /// }
 945     /// ```
 946     pub fn get_def_path(&self, def_id: DefId) -> Vec<Symbol> {
 947         pub struct AbsolutePathPrinter<'tcx> {
 948             pub tcx: TyCtxt<'tcx>,
 949         }
 950
 951         impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 952             type Error = !;
 953
 954             type Path = Vec<Symbol>;
 955             type Region = ();
 956             type Type = ();
 957             type DynExistential = ();
 958             type Const = ();
 959
 960             fn tcx(&self) -> TyCtxt<'tcx> {
 961                 self.tcx
 962             }
 963
 964             fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 965                 Ok(())
 966             }
 967
 968             fn print_type(self, _ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 969                 Ok(())
 970             }
 971
 972             fn print_dyn_existential(
 973                 self,
 974                 _predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
 975             ) -> Result<Self::DynExistential, Self::Error> {
 976                 Ok(())
 977             }
 978
 979             fn print_const(self, _ct: &'tcx ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 980                 Ok(())
 981             }
 982
 983             fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 984                 Ok(vec![self.tcx.crate_name(cnum)])
 985             }
 986
 987             fn path_qualified(
 988                 self,
 989                 self_ty: Ty<'tcx>,
 990                 trait_ref: Option<ty::TraitRef<'tcx>>,
 991             ) -> Result<Self::Path, Self::Error> {
 992                 if trait_ref.is_none() {
 993                     if let ty::Adt(def, substs) = self_ty.kind() {
 994                         return self.print_def_path(def.did, substs);
 995                     }
 996                 }
 997
 998                 // This shouldn't ever be needed, but just in case:
 999                 with_no_trimmed_paths(|| {
1000                     Ok(vec![match trait_ref {
1001                         Some(trait_ref) => Symbol::intern(&format!("{:?}", trait_ref)),
1002                         None => Symbol::intern(&format!("<{}>", self_ty)),
1003                     }])
1004                 })
1005             }
1006
1007             fn path_append_impl(
1008                 self,
1009                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1010                 _disambiguated_data: &DisambiguatedDefPathData,
1011                 self_ty: Ty<'tcx>,
1012                 trait_ref: Option<ty::TraitRef<'tcx>>,
1013             ) -> Result<Self::Path, Self::Error> {
1014                 let mut path = print_prefix(self)?;
1015
1016                 // This shouldn't ever be needed, but just in case:
1017                 path.push(match trait_ref {
1018                     Some(trait_ref) => with_no_trimmed_paths(|| {
1019                         Symbol::intern(&format!(
1020                             "<impl {} for {}>",
1021                             trait_ref.print_only_trait_path(),
1022                             self_ty
1023                         ))
1024                     }),
1025                     None => {
1026                         with_no_trimmed_paths(|| Symbol::intern(&format!("<impl {}>", self_ty)))
1027                     }
1028                 });
1029
1030                 Ok(path)
1031             }
1032
1033             fn path_append(
1034                 self,
1035                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1036                 disambiguated_data: &DisambiguatedDefPathData,
1037             ) -> Result<Self::Path, Self::Error> {
1038                 let mut path = print_prefix(self)?;
1039
1040                 // Skip `::{{constructor}}` on tuple/unit structs.
1041                 if let DefPathData::Ctor = disambiguated_data.data {
1042                     return Ok(path);
1043                 }
1044
1045                 path.push(Symbol::intern(&disambiguated_data.data.to_string()));
1046                 Ok(path)
1047             }
1048
1049             fn path_generic_args(
1050                 self,
1051                 print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
1052                 _args: &[GenericArg<'tcx>],
1053             ) -> Result<Self::Path, Self::Error> {
1054                 print_prefix(self)
1055             }
1056         }
1057
1058         AbsolutePathPrinter { tcx: self.tcx }.print_def_path(def_id, &[]).unwrap()
1059     }
1060 }
1061
1062 impl<'tcx> abi::HasDataLayout for LateContext<'tcx> {
1063     #[inline]
1064     fn data_layout(&self) -> &abi::TargetDataLayout {
1065         &self.tcx.data_layout
1066     }
1067 }
1068
1069 impl<'tcx> ty::layout::HasTyCtxt<'tcx> for LateContext<'tcx> {
1070     #[inline]
1071     fn tcx(&self) -> TyCtxt<'tcx> {
1072         self.tcx
1073     }
1074 }
1075
1076 impl<'tcx> ty::layout::HasParamEnv<'tcx> for LateContext<'tcx> {
1077     #[inline]
1078     fn param_env(&self) -> ty::ParamEnv<'tcx> {
1079         self.param_env
1080     }
1081 }
1082
1083 impl<'tcx> LayoutOfHelpers<'tcx> for LateContext<'tcx> {
1084     type LayoutOfResult = Result<TyAndLayout<'tcx>, LayoutError<'tcx>>;
1085
1086     #[inline]
1087     fn handle_layout_err(&self, err: LayoutError<'tcx>, _: Span, _: Ty<'tcx>) -> LayoutError<'tcx> {
1088         err
1089     }
1090 }
1091
1092 pub fn parse_lint_and_tool_name(lint_name: &str) -> (Option<Symbol>, &str) {
1093     match lint_name.split_once("::") {
1094         Some((tool_name, lint_name)) => {
1095             let tool_name = Symbol::intern(tool_name);
1096
1097             (Some(tool_name), lint_name)
1098         }
1099         None => (None, lint_name),
1100     }
1101 }