compiler/rustc_lint_defs/src/lib.rs

   1 #![feature(min_specialization)]
   2 #![deny(rustc::untranslatable_diagnostic)]
   3 #![deny(rustc::diagnostic_outside_of_impl)]
   4
   5 #[macro_use]
   6 extern crate rustc_macros;
   7
   8 pub use self::Level::*;
   9 use rustc_ast::node_id::NodeId;
  10 use rustc_ast::{AttrId, Attribute};
  11 use rustc_data_structures::fx::FxIndexMap;
  12 use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
  13 use rustc_error_messages::{DiagnosticMessage, MultiSpan};
  14 use rustc_hir::HashStableContext;
  15 use rustc_hir::HirId;
  16 use rustc_span::edition::Edition;
  17 use rustc_span::{sym, symbol::Ident, Span, Symbol};
  18 use rustc_target::spec::abi::Abi;
  19
  20 use serde::{Deserialize, Serialize};
  21
  22 pub mod builtin;
  23
  24 #[macro_export]
  25 macro_rules! pluralize {
  26     ($x:expr) => {
  27         if $x != 1 { "s" } else { "" }
  28     };
  29     ("has", $x:expr) => {
  30         if $x == 1 { "has" } else { "have" }
  31     };
  32     ("is", $x:expr) => {
  33         if $x == 1 { "is" } else { "are" }
  34     };
  35     ("was", $x:expr) => {
  36         if $x == 1 { "was" } else { "were" }
  37     };
  38     ("this", $x:expr) => {
  39         if $x == 1 { "this" } else { "these" }
  40     };
  41 }
  42
  43 /// Indicates the confidence in the correctness of a suggestion.
  44 ///
  45 /// All suggestions are marked with an `Applicability`. Tools use the applicability of a suggestion
  46 /// to determine whether it should be automatically applied or if the user should be consulted
  47 /// before applying the suggestion.
  48 #[derive(Copy, Clone, Debug, Hash, Encodable, Decodable, Serialize, Deserialize)]
  49 #[derive(PartialEq, Eq, PartialOrd, Ord)]
  50 pub enum Applicability {
  51     /// The suggestion is definitely what the user intended, or maintains the exact meaning of the code.
  52     /// This suggestion should be automatically applied.
  53     ///
  54     /// In case of multiple `MachineApplicable` suggestions (whether as part of
  55     /// the same `multipart_suggestion` or not), all of them should be
  56     /// automatically applied.
  57     MachineApplicable,
  58
  59     /// The suggestion may be what the user intended, but it is uncertain. The suggestion should
  60     /// result in valid Rust code if it is applied.
  61     MaybeIncorrect,
  62
  63     /// The suggestion contains placeholders like `(...)` or `{ /* fields */ }`. The suggestion
  64     /// cannot be applied automatically because it will not result in valid Rust code. The user
  65     /// will need to fill in the placeholders.
  66     HasPlaceholders,
  67
  68     /// The applicability of the suggestion is unknown.
  69     Unspecified,
  70 }
  71
  72 /// Each lint expectation has a `LintExpectationId` assigned by the `LintLevelsBuilder`.
  73 /// Expected `Diagnostic`s get the lint level `Expect` which stores the `LintExpectationId`
  74 /// to match it with the actual expectation later on.
  75 ///
  76 /// The `LintExpectationId` has to be stable between compilations, as diagnostic
  77 /// instances might be loaded from cache. Lint messages can be emitted during an
  78 /// `EarlyLintPass` operating on the AST and during a `LateLintPass` traversing the
  79 /// HIR tree. The AST doesn't have enough information to create a stable id. The
  80 /// `LintExpectationId` will instead store the [`AttrId`] defining the expectation.
  81 /// These `LintExpectationId` will be updated to use the stable [`HirId`] once the
  82 /// AST has been lowered. The transformation is done by the `LintLevelsBuilder`
  83 ///
  84 /// Each lint inside the `expect` attribute is tracked individually, the `lint_index`
  85 /// identifies the lint inside the attribute and ensures that the IDs are unique.
  86 ///
  87 /// The index values have a type of `u16` to reduce the size of the `LintExpectationId`.
  88 /// It's reasonable to assume that no user will define 2^16 attributes on one node or
  89 /// have that amount of lints listed. `u16` values should therefore suffice.
  90 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash, Encodable, Decodable)]
  91 pub enum LintExpectationId {
  92     /// Used for lints emitted during the `EarlyLintPass`. This id is not
  93     /// hash stable and should not be cached.
  94     Unstable { attr_id: AttrId, lint_index: Option<u16> },
  95     /// The [`HirId`] that the lint expectation is attached to. This id is
  96     /// stable and can be cached. The additional index ensures that nodes with
  97     /// several expectations can correctly match diagnostics to the individual
  98     /// expectation.
  99     Stable { hir_id: HirId, attr_index: u16, lint_index: Option<u16>, attr_id: Option<AttrId> },
 100 }
 101
 102 impl LintExpectationId {
 103     pub fn is_stable(&self) -> bool {
 104         match self {
 105             LintExpectationId::Unstable { .. } => false,
 106             LintExpectationId::Stable { .. } => true,
 107         }
 108     }
 109
 110     pub fn get_lint_index(&self) -> Option<u16> {
 111         let (LintExpectationId::Unstable { lint_index, .. }
 112         | LintExpectationId::Stable { lint_index, .. }) = self;
 113
 114         *lint_index
 115     }
 116
 117     pub fn set_lint_index(&mut self, new_lint_index: Option<u16>) {
 118         let (LintExpectationId::Unstable { ref mut lint_index, .. }
 119         | LintExpectationId::Stable { ref mut lint_index, .. }) = self;
 120
 121         *lint_index = new_lint_index
 122     }
 123
 124     /// Prepares the id for hashing. Removes references to the ast.
 125     /// Should only be called when the id is stable.
 126     pub fn normalize(self) -> Self {
 127         match self {
 128             Self::Stable { hir_id, attr_index, lint_index, .. } => {
 129                 Self::Stable { hir_id, attr_index, lint_index, attr_id: None }
 130             }
 131             Self::Unstable { .. } => {
 132                 unreachable!("`normalize` called when `ExpectationId` is unstable")
 133             }
 134         }
 135     }
 136 }
 137
 138 impl<HCX: rustc_hir::HashStableContext> HashStable<HCX> for LintExpectationId {
 139     #[inline]
 140     fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
 141         match self {
 142             LintExpectationId::Stable {
 143                 hir_id,
 144                 attr_index,
 145                 lint_index: Some(lint_index),
 146                 attr_id: _,
 147             } => {
 148                 hir_id.hash_stable(hcx, hasher);
 149                 attr_index.hash_stable(hcx, hasher);
 150                 lint_index.hash_stable(hcx, hasher);
 151             }
 152             _ => {
 153                 unreachable!(
 154                     "HashStable should only be called for filled and stable `LintExpectationId`"
 155                 )
 156             }
 157         }
 158     }
 159 }
 160
 161 impl<HCX: rustc_hir::HashStableContext> ToStableHashKey<HCX> for LintExpectationId {
 162     type KeyType = (HirId, u16, u16);
 163
 164     #[inline]
 165     fn to_stable_hash_key(&self, _: &HCX) -> Self::KeyType {
 166         match self {
 167             LintExpectationId::Stable {
 168                 hir_id,
 169                 attr_index,
 170                 lint_index: Some(lint_index),
 171                 attr_id: _,
 172             } => (*hir_id, *attr_index, *lint_index),
 173             _ => {
 174                 unreachable!("HashStable should only be called for a filled `LintExpectationId`")
 175             }
 176         }
 177     }
 178 }
 179
 180 /// Setting for how to handle a lint.
 181 ///
 182 /// See: <https://doc.rust-lang.org/rustc/lints/levels.html>
 183 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash, HashStable_Generic)]
 184 pub enum Level {
 185     /// The `allow` level will not issue any message.
 186     Allow,
 187     /// The `expect` level will suppress the lint message but in turn produce a message
 188     /// if the lint wasn't issued in the expected scope. `Expect` should not be used as
 189     /// an initial level for a lint.
 190     ///
 191     /// Note that this still means that the lint is enabled in this position and should
 192     /// be emitted, this will in turn fulfill the expectation and suppress the lint.
 193     ///
 194     /// See RFC 2383.
 195     ///
 196     /// The [`LintExpectationId`] is used to later link a lint emission to the actual
 197     /// expectation. It can be ignored in most cases.
 198     Expect(LintExpectationId),
 199     /// The `warn` level will produce a warning if the lint was violated, however the
 200     /// compiler will continue with its execution.
 201     Warn,
 202     /// This lint level is a special case of [`Warn`], that can't be overridden. This is used
 203     /// to ensure that a lint can't be suppressed. This lint level can currently only be set
 204     /// via the console and is therefore session specific.
 205     ///
 206     /// The [`LintExpectationId`] is intended to fulfill expectations marked via the
 207     /// `#[expect]` attribute, that will still be suppressed due to the level.
 208     ForceWarn(Option<LintExpectationId>),
 209     /// The `deny` level will produce an error and stop further execution after the lint
 210     /// pass is complete.
 211     Deny,
 212     /// `Forbid` is equivalent to the `deny` level but can't be overwritten like the previous
 213     /// levels.
 214     Forbid,
 215 }
 216
 217 impl Level {
 218     /// Converts a level to a lower-case string.
 219     pub fn as_str(self) -> &'static str {
 220         match self {
 221             Level::Allow => "allow",
 222             Level::Expect(_) => "expect",
 223             Level::Warn => "warn",
 224             Level::ForceWarn(_) => "force-warn",
 225             Level::Deny => "deny",
 226             Level::Forbid => "forbid",
 227         }
 228     }
 229
 230     /// Converts a lower-case string to a level. This will never construct the expect
 231     /// level as that would require a [`LintExpectationId`]
 232     pub fn from_str(x: &str) -> Option<Level> {
 233         match x {
 234             "allow" => Some(Level::Allow),
 235             "warn" => Some(Level::Warn),
 236             "deny" => Some(Level::Deny),
 237             "forbid" => Some(Level::Forbid),
 238             "expect" | _ => None,
 239         }
 240     }
 241
 242     /// Converts a symbol to a level.
 243     pub fn from_attr(attr: &Attribute) -> Option<Level> {
 244         match attr.name_or_empty() {
 245             sym::allow => Some(Level::Allow),
 246             sym::expect => Some(Level::Expect(LintExpectationId::Unstable {
 247                 attr_id: attr.id,
 248                 lint_index: None,
 249             })),
 250             sym::warn => Some(Level::Warn),
 251             sym::deny => Some(Level::Deny),
 252             sym::forbid => Some(Level::Forbid),
 253             _ => None,
 254         }
 255     }
 256
 257     pub fn to_cmd_flag(self) -> &'static str {
 258         match self {
 259             Level::Warn => "-W",
 260             Level::Deny => "-D",
 261             Level::Forbid => "-F",
 262             Level::Allow => "-A",
 263             Level::ForceWarn(_) => "--force-warn",
 264             Level::Expect(_) => {
 265                 unreachable!("the expect level does not have a commandline flag")
 266             }
 267         }
 268     }
 269
 270     pub fn is_error(self) -> bool {
 271         match self {
 272             Level::Allow | Level::Expect(_) | Level::Warn | Level::ForceWarn(_) => false,
 273             Level::Deny | Level::Forbid => true,
 274         }
 275     }
 276
 277     pub fn get_expectation_id(&self) -> Option<LintExpectationId> {
 278         match self {
 279             Level::Expect(id) | Level::ForceWarn(Some(id)) => Some(*id),
 280             _ => None,
 281         }
 282     }
 283 }
 284
 285 /// Specification of a single lint.
 286 #[derive(Copy, Clone, Debug)]
 287 pub struct Lint {
 288     /// A string identifier for the lint.
 289     ///
 290     /// This identifies the lint in attributes and in command-line arguments.
 291     /// In those contexts it is always lowercase, but this field is compared
 292     /// in a way which is case-insensitive for ASCII characters. This allows
 293     /// `declare_lint!()` invocations to follow the convention of upper-case
 294     /// statics without repeating the name.
 295     ///
 296     /// The name is written with underscores, e.g., "unused_imports".
 297     /// On the command line, underscores become dashes.
 298     ///
 299     /// See <https://rustc-dev-guide.rust-lang.org/diagnostics.html#lint-naming>
 300     /// for naming guidelines.
 301     pub name: &'static str,
 302
 303     /// Default level for the lint.
 304     ///
 305     /// See <https://rustc-dev-guide.rust-lang.org/diagnostics.html#diagnostic-levels>
 306     /// for guidelines on choosing a default level.
 307     pub default_level: Level,
 308
 309     /// Description of the lint or the issue it detects.
 310     ///
 311     /// e.g., "imports that are never used"
 312     pub desc: &'static str,
 313
 314     /// Starting at the given edition, default to the given lint level. If this is `None`, then use
 315     /// `default_level`.
 316     pub edition_lint_opts: Option<(Edition, Level)>,
 317
 318     /// `true` if this lint is reported even inside expansions of external macros.
 319     pub report_in_external_macro: bool,
 320
 321     pub future_incompatible: Option<FutureIncompatibleInfo>,
 322
 323     pub is_plugin: bool,
 324
 325     /// `Some` if this lint is feature gated, otherwise `None`.
 326     pub feature_gate: Option<Symbol>,
 327
 328     pub crate_level_only: bool,
 329 }
 330
 331 /// Extra information for a future incompatibility lint.
 332 #[derive(Copy, Clone, Debug)]
 333 pub struct FutureIncompatibleInfo {
 334     /// e.g., a URL for an issue/PR/RFC or error code
 335     pub reference: &'static str,
 336     /// The reason for the lint used by diagnostics to provide
 337     /// the right help message
 338     pub reason: FutureIncompatibilityReason,
 339     /// Whether to explain the reason to the user.
 340     ///
 341     /// Set to false for lints that already include a more detailed
 342     /// explanation.
 343     pub explain_reason: bool,
 344 }
 345
 346 /// The reason for future incompatibility
 347 #[derive(Copy, Clone, Debug)]
 348 pub enum FutureIncompatibilityReason {
 349     /// This will be an error in a future release
 350     /// for all editions
 351     FutureReleaseError,
 352     /// This will be an error in a future release, and
 353     /// Cargo should create a report even for dependencies
 354     FutureReleaseErrorReportNow,
 355     /// Code that changes meaning in some way in a
 356     /// future release.
 357     FutureReleaseSemanticsChange,
 358     /// Previously accepted code that will become an
 359     /// error in the provided edition
 360     EditionError(Edition),
 361     /// Code that changes meaning in some way in
 362     /// the provided edition
 363     EditionSemanticsChange(Edition),
 364     /// A custom reason.
 365     Custom(&'static str),
 366 }
 367
 368 impl FutureIncompatibilityReason {
 369     pub fn edition(self) -> Option<Edition> {
 370         match self {
 371             Self::EditionError(e) => Some(e),
 372             Self::EditionSemanticsChange(e) => Some(e),
 373             _ => None,
 374         }
 375     }
 376 }
 377
 378 impl FutureIncompatibleInfo {
 379     pub const fn default_fields_for_macro() -> Self {
 380         FutureIncompatibleInfo {
 381             reference: "",
 382             reason: FutureIncompatibilityReason::FutureReleaseError,
 383             explain_reason: true,
 384         }
 385     }
 386 }
 387
 388 impl Lint {
 389     pub const fn default_fields_for_macro() -> Self {
 390         Lint {
 391             name: "",
 392             default_level: Level::Forbid,
 393             desc: "",
 394             edition_lint_opts: None,
 395             is_plugin: false,
 396             report_in_external_macro: false,
 397             future_incompatible: None,
 398             feature_gate: None,
 399             crate_level_only: false,
 400         }
 401     }
 402
 403     /// Gets the lint's name, with ASCII letters converted to lowercase.
 404     pub fn name_lower(&self) -> String {
 405         self.name.to_ascii_lowercase()
 406     }
 407
 408     pub fn default_level(&self, edition: Edition) -> Level {
 409         self.edition_lint_opts
 410             .filter(|(e, _)| *e <= edition)
 411             .map(|(_, l)| l)
 412             .unwrap_or(self.default_level)
 413     }
 414 }
 415
 416 /// Identifies a lint known to the compiler.
 417 #[derive(Clone, Copy, Debug)]
 418 pub struct LintId {
 419     // Identity is based on pointer equality of this field.
 420     pub lint: &'static Lint,
 421 }
 422
 423 impl PartialEq for LintId {
 424     fn eq(&self, other: &LintId) -> bool {
 425         std::ptr::eq(self.lint, other.lint)
 426     }
 427 }
 428
 429 impl Eq for LintId {}
 430
 431 impl std::hash::Hash for LintId {
 432     fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
 433         let ptr = self.lint as *const Lint;
 434         ptr.hash(state);
 435     }
 436 }
 437
 438 impl LintId {
 439     /// Gets the `LintId` for a `Lint`.
 440     pub fn of(lint: &'static Lint) -> LintId {
 441         LintId { lint }
 442     }
 443
 444     pub fn lint_name_raw(&self) -> &'static str {
 445         self.lint.name
 446     }
 447
 448     /// Gets the name of the lint.
 449     pub fn to_string(&self) -> String {
 450         self.lint.name_lower()
 451     }
 452 }
 453
 454 impl<HCX> HashStable<HCX> for LintId {
 455     #[inline]
 456     fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
 457         self.lint_name_raw().hash_stable(hcx, hasher);
 458     }
 459 }
 460
 461 impl<HCX> ToStableHashKey<HCX> for LintId {
 462     type KeyType = &'static str;
 463
 464     #[inline]
 465     fn to_stable_hash_key(&self, _: &HCX) -> &'static str {
 466         self.lint_name_raw()
 467     }
 468 }
 469
 470 // This could be a closure, but then implementing derive trait
 471 // becomes hacky (and it gets allocated).
 472 #[derive(Debug)]
 473 pub enum BuiltinLintDiagnostics {
 474     Normal,
 475     AbsPathWithModule(Span),
 476     ProcMacroDeriveResolutionFallback(Span),
 477     MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
 478     ElidedLifetimesInPaths(usize, Span, bool, Span),
 479     UnknownCrateTypes(Span, String, String),
 480     UnusedImports(String, Vec<(Span, String)>, Option<Span>),
 481     RedundantImport(Vec<(Span, bool)>, Ident),
 482     DeprecatedMacro(Option<Symbol>, Span),
 483     MissingAbi(Span, Abi),
 484     UnusedDocComment(Span),
 485     UnusedBuiltinAttribute {
 486         attr_name: Symbol,
 487         macro_name: String,
 488         invoc_span: Span,
 489     },
 490     PatternsInFnsWithoutBody(Span, Ident),
 491     LegacyDeriveHelpers(Span),
 492     ProcMacroBackCompat(String),
 493     OrPatternsBackCompat(Span, String),
 494     ReservedPrefix(Span),
 495     TrailingMacro(bool, Ident),
 496     BreakWithLabelAndLoop(Span),
 497     NamedAsmLabel(String),
 498     UnicodeTextFlow(Span, String),
 499     UnexpectedCfg((Symbol, Span), Option<(Symbol, Span)>),
 500     DeprecatedWhereclauseLocation(Span, String),
 501     SingleUseLifetime {
 502         /// Span of the parameter which declares this lifetime.
 503         param_span: Span,
 504         /// Span of the code that should be removed when eliding this lifetime.
 505         /// This span should include leading or trailing comma.
 506         deletion_span: Option<Span>,
 507         /// Span of the single use, or None if the lifetime is never used.
 508         /// If true, the lifetime will be fully elided.
 509         use_span: Option<(Span, bool)>,
 510     },
 511     NamedArgumentUsedPositionally {
 512         /// Span where the named argument is used by position and will be replaced with the named
 513         /// argument name
 514         position_sp_to_replace: Option<Span>,
 515         /// Span where the named argument is used by position and is used for lint messages
 516         position_sp_for_msg: Option<Span>,
 517         /// Span where the named argument's name is (so we know where to put the warning message)
 518         named_arg_sp: Span,
 519         /// String containing the named arguments name
 520         named_arg_name: String,
 521         /// Indicates if the named argument is used as a width/precision for formatting
 522         is_formatting_arg: bool,
 523     },
 524 }
 525
 526 /// Lints that are buffered up early on in the `Session` before the
 527 /// `LintLevels` is calculated.
 528 pub struct BufferedEarlyLint {
 529     /// The span of code that we are linting on.
 530     pub span: MultiSpan,
 531
 532     /// The lint message.
 533     pub msg: DiagnosticMessage,
 534
 535     /// The `NodeId` of the AST node that generated the lint.
 536     pub node_id: NodeId,
 537
 538     /// A lint Id that can be passed to
 539     /// `rustc_lint::early::EarlyContextAndPass::check_id`.
 540     pub lint_id: LintId,
 541
 542     /// Customization of the `DiagnosticBuilder<'_>` for the lint.
 543     pub diagnostic: BuiltinLintDiagnostics,
 544 }
 545
 546 #[derive(Default)]
 547 pub struct LintBuffer {
 548     pub map: FxIndexMap<NodeId, Vec<BufferedEarlyLint>>,
 549 }
 550
 551 impl LintBuffer {
 552     pub fn add_early_lint(&mut self, early_lint: BufferedEarlyLint) {
 553         let arr = self.map.entry(early_lint.node_id).or_default();
 554         arr.push(early_lint);
 555     }
 556
 557     pub fn add_lint(
 558         &mut self,
 559         lint: &'static Lint,
 560         node_id: NodeId,
 561         span: MultiSpan,
 562         msg: impl Into<DiagnosticMessage>,
 563         diagnostic: BuiltinLintDiagnostics,
 564     ) {
 565         let lint_id = LintId::of(lint);
 566         let msg = msg.into();
 567         self.add_early_lint(BufferedEarlyLint { lint_id, node_id, span, msg, diagnostic });
 568     }
 569
 570     pub fn take(&mut self, id: NodeId) -> Vec<BufferedEarlyLint> {
 571         self.map.remove(&id).unwrap_or_default()
 572     }
 573
 574     pub fn buffer_lint(
 575         &mut self,
 576         lint: &'static Lint,
 577         id: NodeId,
 578         sp: impl Into<MultiSpan>,
 579         msg: impl Into<DiagnosticMessage>,
 580     ) {
 581         self.add_lint(lint, id, sp.into(), msg, BuiltinLintDiagnostics::Normal)
 582     }
 583
 584     pub fn buffer_lint_with_diagnostic(
 585         &mut self,
 586         lint: &'static Lint,
 587         id: NodeId,
 588         sp: impl Into<MultiSpan>,
 589         msg: impl Into<DiagnosticMessage>,
 590         diagnostic: BuiltinLintDiagnostics,
 591     ) {
 592         self.add_lint(lint, id, sp.into(), msg, diagnostic)
 593     }
 594 }
 595
 596 /// Declares a static item of type `&'static Lint`.
 597 ///
 598 /// See <https://rustc-dev-guide.rust-lang.org/diagnostics.html> for
 599 /// documentation and guidelines on writing lints.
 600 ///
 601 /// The macro call should start with a doc comment explaining the lint
 602 /// which will be embedded in the rustc user documentation book. It should
 603 /// be written in markdown and have a format that looks like this:
 604 ///
 605 /// ```rust,ignore (doc-example)
 606 /// /// The `my_lint_name` lint detects [short explanation here].
 607 /// ///
 608 /// /// ### Example
 609 /// ///
 610 /// /// ```rust
 611 /// /// [insert a concise example that triggers the lint]
 612 /// /// ```
 613 /// ///
 614 /// /// {{produces}}
 615 /// ///
 616 /// /// ### Explanation
 617 /// ///
 618 /// /// This should be a detailed explanation of *why* the lint exists,
 619 /// /// and also include suggestions on how the user should fix the problem.
 620 /// /// Try to keep the text simple enough that a beginner can understand,
 621 /// /// and include links to other documentation for terminology that a
 622 /// /// beginner may not be familiar with. If this is "allow" by default,
 623 /// /// it should explain why (are there false positives or other issues?). If
 624 /// /// this is a future-incompatible lint, it should say so, with text that
 625 /// /// looks roughly like this:
 626 /// ///
 627 /// /// This is a [future-incompatible] lint to transition this to a hard
 628 /// /// error in the future. See [issue #xxxxx] for more details.
 629 /// ///
 630 /// /// [issue #xxxxx]: https://github.com/rust-lang/rust/issues/xxxxx
 631 /// ```
 632 ///
 633 /// The `{{produces}}` tag will be automatically replaced with the output from
 634 /// the example by the build system. If the lint example is too complex to run
 635 /// as a simple example (for example, it needs an extern crate), mark the code
 636 /// block with `ignore` and manually replace the `{{produces}}` line with the
 637 /// expected output in a `text` code block.
 638 ///
 639 /// If this is a rustdoc-only lint, then only include a brief introduction
 640 /// with a link with the text `[rustdoc book]` so that the validator knows
 641 /// that this is for rustdoc only (see BROKEN_INTRA_DOC_LINKS as an example).
 642 ///
 643 /// Commands to view and test the documentation:
 644 ///
 645 /// * `./x.py doc --stage=1 src/doc/rustc --open`: Builds the rustc book and opens it.
 646 /// * `./x.py test src/tools/lint-docs`: Validates that the lint docs have the
 647 ///   correct style, and that the code example actually emits the expected
 648 ///   lint.
 649 ///
 650 /// If you have already built the compiler, and you want to make changes to
 651 /// just the doc comments, then use the `--keep-stage=0` flag with the above
 652 /// commands to avoid rebuilding the compiler.
 653 #[macro_export]
 654 macro_rules! declare_lint {
 655     ($(#[$attr:meta])* $vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
 656         $crate::declare_lint!(
 657             $(#[$attr])* $vis $NAME, $Level, $desc,
 658         );
 659     );
 660     ($(#[$attr:meta])* $vis: vis $NAME: ident, $Level: ident, $desc: expr,
 661      $(@feature_gate = $gate:expr;)?
 662      $(@future_incompatible = FutureIncompatibleInfo { $($field:ident : $val:expr),* $(,)*  }; )?
 663      $($v:ident),*) => (
 664         $(#[$attr])*
 665         $vis static $NAME: &$crate::Lint = &$crate::Lint {
 666             name: stringify!($NAME),
 667             default_level: $crate::$Level,
 668             desc: $desc,
 669             edition_lint_opts: None,
 670             is_plugin: false,
 671             $($v: true,)*
 672             $(feature_gate: Some($gate),)*
 673             $(future_incompatible: Some($crate::FutureIncompatibleInfo {
 674                 $($field: $val,)*
 675                 ..$crate::FutureIncompatibleInfo::default_fields_for_macro()
 676             }),)*
 677             ..$crate::Lint::default_fields_for_macro()
 678         };
 679     );
 680     ($(#[$attr:meta])* $vis: vis $NAME: ident, $Level: ident, $desc: expr,
 681      $lint_edition: expr => $edition_level: ident
 682     ) => (
 683         $(#[$attr])*
 684         $vis static $NAME: &$crate::Lint = &$crate::Lint {
 685             name: stringify!($NAME),
 686             default_level: $crate::$Level,
 687             desc: $desc,
 688             edition_lint_opts: Some(($lint_edition, $crate::Level::$edition_level)),
 689             report_in_external_macro: false,
 690             is_plugin: false,
 691         };
 692     );
 693 }
 694
 695 #[macro_export]
 696 macro_rules! declare_tool_lint {
 697     (
 698         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level: ident, $desc: expr
 699         $(, @feature_gate = $gate:expr;)?
 700     ) => (
 701         $crate::declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, false $(, @feature_gate = $gate;)?}
 702     );
 703     (
 704         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level:ident, $desc:expr,
 705         report_in_external_macro: $rep:expr
 706         $(, @feature_gate = $gate:expr;)?
 707     ) => (
 708          $crate::declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, $rep $(, @feature_gate = $gate;)?}
 709     );
 710     (
 711         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level:ident, $desc:expr,
 712         $external:expr
 713         $(, @feature_gate = $gate:expr;)?
 714     ) => (
 715         $(#[$attr])*
 716         $vis static $NAME: &$crate::Lint = &$crate::Lint {
 717             name: &concat!(stringify!($tool), "::", stringify!($NAME)),
 718             default_level: $crate::$Level,
 719             desc: $desc,
 720             edition_lint_opts: None,
 721             report_in_external_macro: $external,
 722             future_incompatible: None,
 723             is_plugin: true,
 724             $(feature_gate: Some($gate),)?
 725             crate_level_only: false,
 726             ..$crate::Lint::default_fields_for_macro()
 727         };
 728     );
 729 }
 730
 731 /// Declares a static `LintArray` and return it as an expression.
 732 #[macro_export]
 733 macro_rules! lint_array {
 734     ($( $lint:expr ),* ,) => { lint_array!( $($lint),* ) };
 735     ($( $lint:expr ),*) => {{
 736         vec![$($lint),*]
 737     }}
 738 }
 739
 740 pub type LintArray = Vec<&'static Lint>;
 741
 742 pub trait LintPass {
 743     fn name(&self) -> &'static str;
 744 }
 745
 746 /// Implements `LintPass for $ty` with the given list of `Lint` statics.
 747 #[macro_export]
 748 macro_rules! impl_lint_pass {
 749     ($ty:ty => [$($lint:expr),* $(,)?]) => {
 750         impl $crate::LintPass for $ty {
 751             fn name(&self) -> &'static str { stringify!($ty) }
 752         }
 753         impl $ty {
 754             pub fn get_lints() -> $crate::LintArray { $crate::lint_array!($($lint),*) }
 755         }
 756     };
 757 }
 758
 759 /// Declares a type named `$name` which implements `LintPass`.
 760 /// To the right of `=>` a comma separated list of `Lint` statics is given.
 761 #[macro_export]
 762 macro_rules! declare_lint_pass {
 763     ($(#[$m:meta])* $name:ident => [$($lint:expr),* $(,)?]) => {
 764         $(#[$m])* #[derive(Copy, Clone)] pub struct $name;
 765         $crate::impl_lint_pass!($name => [$($lint),*]);
 766     };
 767 }