1 //! Lints, aka compiler warnings.
3 //! A 'lint' check is a kind of miscellaneous constraint that a user _might_
4 //! want to enforce, but might reasonably want to permit as well, on a
5 //! module-by-module basis. They contrast with static constraints enforced by
6 //! other phases of the compiler, which are generally required to hold in order
7 //! to compile the program at all.
9 //! Most lints can be written as `LintPass` instances. These run after
10 //! all other analyses. The `LintPass`es built into rustc are defined
11 //! within `builtin.rs`, which has further comments on how to add such a lint.
12 //! rustc can also load user-defined lint plugins via the plugin mechanism.
14 //! Some of rustc's lints are defined elsewhere in the compiler and work by
15 //! calling `add_lint()` on the overall `Session` object. This works when
16 //! it happens before the main lint pass, which emits the lints stored by
17 //! `add_lint()`. To emit lints after the main lint pass (from codegen, for
18 //! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
21 pub use self::Level::*;
22 pub use self::LintSource::*;
24 use rustc_data_structures::sync;
26 use crate::hir::def_id::{CrateNum, LOCAL_CRATE};
27 use crate::hir::intravisit;
29 use crate::lint::builtin::BuiltinLintDiagnostics;
30 use crate::lint::builtin::parser::{ILL_FORMED_ATTRIBUTE_INPUT, META_VARIABLE_MISUSE};
31 use crate::session::{Session, DiagnosticMessageId};
32 use crate::ty::TyCtxt;
33 use crate::ty::query::Providers;
34 use crate::util::nodemap::NodeMap;
35 use errors::{DiagnosticBuilder, DiagnosticId};
38 use syntax::source_map::{MultiSpan, ExpnKind, DesugaringKind};
39 use syntax::early_buffered_lints::BufferedEarlyLintId;
40 use syntax::edition::Edition;
41 use syntax::ext::base::MacroKind;
42 use syntax::symbol::{Symbol, sym};
45 pub use crate::lint::context::{LateContext, EarlyContext, LintContext, LintStore,
46 check_crate, check_ast_crate, late_lint_mod, CheckLintNameResult,
47 FutureIncompatibleInfo, BufferedEarlyLint,};
49 /// Specification of a single lint.
50 #[derive(Copy, Clone, Debug)]
52 /// A string identifier for the lint.
54 /// This identifies the lint in attributes and in command-line arguments.
55 /// In those contexts it is always lowercase, but this field is compared
56 /// in a way which is case-insensitive for ASCII characters. This allows
57 /// `declare_lint!()` invocations to follow the convention of upper-case
58 /// statics without repeating the name.
60 /// The name is written with underscores, e.g., "unused_imports".
61 /// On the command line, underscores become dashes.
62 pub name: &'static str,
64 /// Default level for the lint.
65 pub default_level: Level,
67 /// Description of the lint or the issue it detects.
69 /// e.g., "imports that are never used"
70 pub desc: &'static str,
72 /// Starting at the given edition, default to the given lint level. If this is `None`, then use
74 pub edition_lint_opts: Option<(Edition, Level)>,
76 /// `true` if this lint is reported even inside expansions of external macros.
77 pub report_in_external_macro: bool,
81 /// Returns the `rust::lint::Lint` for a `syntax::early_buffered_lints::BufferedEarlyLintId`.
82 pub fn from_parser_lint_id(lint_id: BufferedEarlyLintId) -> &'static Self {
84 BufferedEarlyLintId::IllFormedAttributeInput => ILL_FORMED_ATTRIBUTE_INPUT,
85 BufferedEarlyLintId::MetaVariableMisuse => META_VARIABLE_MISUSE,
89 /// Gets the lint's name, with ASCII letters converted to lowercase.
90 pub fn name_lower(&self) -> String {
91 self.name.to_ascii_lowercase()
94 pub fn default_level(&self, session: &Session) -> Level {
95 self.edition_lint_opts
96 .filter(|(e, _)| *e <= session.edition())
98 .unwrap_or(self.default_level)
102 /// Declares a static item of type `&'static Lint`.
104 macro_rules! declare_lint {
105 ($vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
106 declare_lint!{$vis $NAME, $Level, $desc, false}
108 ($vis: vis $NAME: ident, $Level: ident, $desc: expr, report_in_external_macro: $rep: expr) => (
109 declare_lint!{$vis $NAME, $Level, $desc, $rep}
111 ($vis: vis $NAME: ident, $Level: ident, $desc: expr, $external: expr) => (
112 $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
113 name: stringify!($NAME),
114 default_level: $crate::lint::$Level,
116 edition_lint_opts: None,
117 report_in_external_macro: $external,
120 ($vis: vis $NAME: ident, $Level: ident, $desc: expr,
121 $lint_edition: expr => $edition_level: ident
123 $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
124 name: stringify!($NAME),
125 default_level: $crate::lint::$Level,
127 edition_lint_opts: Some(($lint_edition, $crate::lint::Level::$edition_level)),
128 report_in_external_macro: false,
134 macro_rules! declare_tool_lint {
136 $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level: ident, $desc: expr
138 declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, false}
141 $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level:ident, $desc:expr,
142 report_in_external_macro: $rep:expr
144 declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, $rep}
147 $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level:ident, $desc:expr,
151 $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
152 name: &concat!(stringify!($tool), "::", stringify!($NAME)),
153 default_level: $crate::lint::$Level,
155 edition_lint_opts: None,
156 report_in_external_macro: $external,
161 /// Declares a static `LintArray` and return it as an expression.
163 macro_rules! lint_array {
164 ($( $lint:expr ),* ,) => { lint_array!( $($lint),* ) };
165 ($( $lint:expr ),*) => {{
170 pub type LintArray = Vec<&'static Lint>;
173 fn name(&self) -> &'static str;
175 /// Gets descriptions of the lints this `LintPass` object can emit.
177 /// N.B., there is no enforcement that the object only emits lints it registered.
178 /// And some `rustc` internal `LintPass`es register lints to be emitted by other
179 /// parts of the compiler. If you want enforced access restrictions for your
180 /// `Lint`, make it a private `static` item in its own module.
181 fn get_lints(&self) -> LintArray;
184 /// Implements `LintPass for $name` with the given list of `Lint` statics.
186 macro_rules! impl_lint_pass {
187 ($name:ident => [$($lint:expr),* $(,)?]) => {
188 impl LintPass for $name {
189 fn name(&self) -> &'static str { stringify!($name) }
190 fn get_lints(&self) -> LintArray { $crate::lint_array!($($lint),*) }
195 /// Declares a type named `$name` which implements `LintPass`.
196 /// To the right of `=>` a comma separated list of `Lint` statics is given.
198 macro_rules! declare_lint_pass {
199 ($(#[$m:meta])* $name:ident => [$($lint:expr),* $(,)?]) => {
200 $(#[$m])* #[derive(Copy, Clone)] pub struct $name;
201 $crate::impl_lint_pass!($name => [$($lint),*]);
206 macro_rules! late_lint_methods {
207 ($macro:path, $args:tt, [$hir:tt]) => (
208 $macro!($args, [$hir], [
209 fn check_param(a: &$hir hir::Param);
210 fn check_body(a: &$hir hir::Body);
211 fn check_body_post(a: &$hir hir::Body);
212 fn check_name(a: Span, b: ast::Name);
213 fn check_crate(a: &$hir hir::Crate);
214 fn check_crate_post(a: &$hir hir::Crate);
215 fn check_mod(a: &$hir hir::Mod, b: Span, c: hir::HirId);
216 fn check_mod_post(a: &$hir hir::Mod, b: Span, c: hir::HirId);
217 fn check_foreign_item(a: &$hir hir::ForeignItem);
218 fn check_foreign_item_post(a: &$hir hir::ForeignItem);
219 fn check_item(a: &$hir hir::Item);
220 fn check_item_post(a: &$hir hir::Item);
221 fn check_local(a: &$hir hir::Local);
222 fn check_block(a: &$hir hir::Block);
223 fn check_block_post(a: &$hir hir::Block);
224 fn check_stmt(a: &$hir hir::Stmt);
225 fn check_arm(a: &$hir hir::Arm);
226 fn check_pat(a: &$hir hir::Pat);
227 fn check_expr(a: &$hir hir::Expr);
228 fn check_expr_post(a: &$hir hir::Expr);
229 fn check_ty(a: &$hir hir::Ty);
230 fn check_generic_param(a: &$hir hir::GenericParam);
231 fn check_generics(a: &$hir hir::Generics);
232 fn check_where_predicate(a: &$hir hir::WherePredicate);
233 fn check_poly_trait_ref(a: &$hir hir::PolyTraitRef, b: hir::TraitBoundModifier);
235 a: hir::intravisit::FnKind<$hir>,
236 b: &$hir hir::FnDecl,
241 a: hir::intravisit::FnKind<$hir>,
242 b: &$hir hir::FnDecl,
247 fn check_trait_item(a: &$hir hir::TraitItem);
248 fn check_trait_item_post(a: &$hir hir::TraitItem);
249 fn check_impl_item(a: &$hir hir::ImplItem);
250 fn check_impl_item_post(a: &$hir hir::ImplItem);
251 fn check_struct_def(a: &$hir hir::VariantData);
252 fn check_struct_def_post(a: &$hir hir::VariantData);
253 fn check_struct_field(a: &$hir hir::StructField);
254 fn check_variant(a: &$hir hir::Variant);
255 fn check_variant_post(a: &$hir hir::Variant);
256 fn check_lifetime(a: &$hir hir::Lifetime);
257 fn check_path(a: &$hir hir::Path, b: hir::HirId);
258 fn check_attribute(a: &$hir ast::Attribute);
260 /// Called when entering a syntax node that can have lint attributes such
261 /// as `#[allow(...)]`. Called with *all* the attributes of that node.
262 fn enter_lint_attrs(a: &$hir [ast::Attribute]);
264 /// Counterpart to `enter_lint_attrs`.
265 fn exit_lint_attrs(a: &$hir [ast::Attribute]);
270 /// Trait for types providing lint checks.
272 /// Each `check` method checks a single syntax node, and should not
273 /// invoke methods recursively (unlike `Visitor`). By default they
276 // FIXME: eliminate the duplication with `Visitor`. But this also
277 // contains a few lint-specific methods with no equivalent in `Visitor`.
279 macro_rules! expand_lint_pass_methods {
280 ($context:ty, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
281 $(#[inline(always)] fn $name(&mut self, _: $context, $(_: $arg),*) {})*
285 macro_rules! declare_late_lint_pass {
286 ([], [$hir:tt], [$($methods:tt)*]) => (
287 pub trait LateLintPass<'a, $hir>: LintPass {
288 fn fresh_late_pass(&self) -> LateLintPassObject {
291 expand_lint_pass_methods!(&LateContext<'a, $hir>, [$($methods)*]);
296 late_lint_methods!(declare_late_lint_pass, [], ['tcx]);
299 macro_rules! expand_combined_late_lint_pass_method {
300 ([$($passes:ident),*], $self: ident, $name: ident, $params:tt) => ({
301 $($self.$passes.$name $params;)*
306 macro_rules! expand_combined_late_lint_pass_methods {
307 ($passes:tt, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
308 $(fn $name(&mut self, context: &LateContext<'a, 'tcx>, $($param: $arg),*) {
309 expand_combined_late_lint_pass_method!($passes, self, $name, (context, $($param),*));
315 macro_rules! declare_combined_late_lint_pass {
316 ([$v:vis $name:ident, [$($passes:ident: $constructor:expr,)*]], [$hir:tt], $methods:tt) => (
317 #[allow(non_snake_case)]
319 $($passes: $passes,)*
323 $v fn new() -> Self {
325 $($passes: $constructor,)*
330 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for $name {
331 expand_combined_late_lint_pass_methods!([$($passes),*], $methods);
334 impl LintPass for $name {
335 fn name(&self) -> &'static str {
339 fn get_lints(&self) -> LintArray {
340 let mut lints = Vec::new();
341 $(lints.extend_from_slice(&self.$passes.get_lints());)*
349 macro_rules! early_lint_methods {
350 ($macro:path, $args:tt) => (
352 fn check_param(a: &ast::Param);
353 fn check_ident(a: ast::Ident);
354 fn check_crate(a: &ast::Crate);
355 fn check_crate_post(a: &ast::Crate);
356 fn check_mod(a: &ast::Mod, b: Span, c: ast::NodeId);
357 fn check_mod_post(a: &ast::Mod, b: Span, c: ast::NodeId);
358 fn check_foreign_item(a: &ast::ForeignItem);
359 fn check_foreign_item_post(a: &ast::ForeignItem);
360 fn check_item(a: &ast::Item);
361 fn check_item_post(a: &ast::Item);
362 fn check_local(a: &ast::Local);
363 fn check_block(a: &ast::Block);
364 fn check_block_post(a: &ast::Block);
365 fn check_stmt(a: &ast::Stmt);
366 fn check_arm(a: &ast::Arm);
367 fn check_pat(a: &ast::Pat);
368 fn check_pat_post(a: &ast::Pat);
369 fn check_expr(a: &ast::Expr);
370 fn check_expr_post(a: &ast::Expr);
371 fn check_ty(a: &ast::Ty);
372 fn check_generic_param(a: &ast::GenericParam);
373 fn check_generics(a: &ast::Generics);
374 fn check_where_predicate(a: &ast::WherePredicate);
375 fn check_poly_trait_ref(a: &ast::PolyTraitRef,
376 b: &ast::TraitBoundModifier);
377 fn check_fn(a: syntax::visit::FnKind<'_>, b: &ast::FnDecl, c: Span, d_: ast::NodeId);
379 a: syntax::visit::FnKind<'_>,
384 fn check_trait_item(a: &ast::TraitItem);
385 fn check_trait_item_post(a: &ast::TraitItem);
386 fn check_impl_item(a: &ast::ImplItem);
387 fn check_impl_item_post(a: &ast::ImplItem);
388 fn check_struct_def(a: &ast::VariantData);
389 fn check_struct_def_post(a: &ast::VariantData);
390 fn check_struct_field(a: &ast::StructField);
391 fn check_variant(a: &ast::Variant);
392 fn check_variant_post(a: &ast::Variant);
393 fn check_lifetime(a: &ast::Lifetime);
394 fn check_path(a: &ast::Path, b: ast::NodeId);
395 fn check_attribute(a: &ast::Attribute);
396 fn check_mac_def(a: &ast::MacroDef, b: ast::NodeId);
397 fn check_mac(a: &ast::Mac);
399 /// Called when entering a syntax node that can have lint attributes such
400 /// as `#[allow(...)]`. Called with *all* the attributes of that node.
401 fn enter_lint_attrs(a: &[ast::Attribute]);
403 /// Counterpart to `enter_lint_attrs`.
404 fn exit_lint_attrs(a: &[ast::Attribute]);
409 macro_rules! expand_early_lint_pass_methods {
410 ($context:ty, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
411 $(#[inline(always)] fn $name(&mut self, _: $context, $(_: $arg),*) {})*
415 macro_rules! declare_early_lint_pass {
416 ([], [$($methods:tt)*]) => (
417 pub trait EarlyLintPass: LintPass {
418 expand_early_lint_pass_methods!(&EarlyContext<'_>, [$($methods)*]);
423 early_lint_methods!(declare_early_lint_pass, []);
426 macro_rules! expand_combined_early_lint_pass_method {
427 ([$($passes:ident),*], $self: ident, $name: ident, $params:tt) => ({
428 $($self.$passes.$name $params;)*
433 macro_rules! expand_combined_early_lint_pass_methods {
434 ($passes:tt, [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
435 $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
436 expand_combined_early_lint_pass_method!($passes, self, $name, (context, $($param),*));
442 macro_rules! declare_combined_early_lint_pass {
443 ([$v:vis $name:ident, [$($passes:ident: $constructor:expr,)*]], $methods:tt) => (
444 #[allow(non_snake_case)]
446 $($passes: $passes,)*
450 $v fn new() -> Self {
452 $($passes: $constructor,)*
457 impl EarlyLintPass for $name {
458 expand_combined_early_lint_pass_methods!([$($passes),*], $methods);
461 impl LintPass for $name {
462 fn name(&self) -> &'static str {
466 fn get_lints(&self) -> LintArray {
467 let mut lints = Vec::new();
468 $(lints.extend_from_slice(&self.$passes.get_lints());)*
475 /// A lint pass boxed up as a trait object.
476 pub type EarlyLintPassObject = Box<dyn EarlyLintPass + sync::Send + sync::Sync + 'static>;
477 pub type LateLintPassObject = Box<dyn for<'a, 'tcx> LateLintPass<'a, 'tcx> + sync::Send
478 + sync::Sync + 'static>;
480 /// Identifies a lint known to the compiler.
481 #[derive(Clone, Copy, Debug)]
483 // Identity is based on pointer equality of this field.
487 impl PartialEq for LintId {
488 fn eq(&self, other: &LintId) -> bool {
489 ptr::eq(self.lint, other.lint)
493 impl Eq for LintId { }
495 impl hash::Hash for LintId {
496 fn hash<H: hash::Hasher>(&self, state: &mut H) {
497 let ptr = self.lint as *const Lint;
503 /// Gets the `LintId` for a `Lint`.
504 pub fn of(lint: &'static Lint) -> LintId {
510 pub fn lint_name_raw(&self) -> &'static str {
514 /// Gets the name of the lint.
515 pub fn to_string(&self) -> String {
516 self.lint.name_lower()
520 /// Setting for how to handle a lint.
521 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
523 Allow, Warn, Deny, Forbid,
526 impl_stable_hash_for!(enum self::Level {
534 /// Converts a level to a lower-case string.
535 pub fn as_str(self) -> &'static str {
544 /// Converts a lower-case string to a level.
545 pub fn from_str(x: &str) -> Option<Level> {
547 "allow" => Some(Allow),
548 "warn" => Some(Warn),
549 "deny" => Some(Deny),
550 "forbid" => Some(Forbid),
555 /// Converts a symbol to a level.
556 pub fn from_symbol(x: Symbol) -> Option<Level> {
558 sym::allow => Some(Allow),
559 sym::warn => Some(Warn),
560 sym::deny => Some(Deny),
561 sym::forbid => Some(Forbid),
567 /// How a lint level was set.
568 #[derive(Clone, Copy, PartialEq, Eq)]
569 pub enum LintSource {
570 /// Lint is at the default level as declared
571 /// in rustc or a plugin.
574 /// Lint level was set by an attribute.
575 Node(ast::Name, Span, Option<Symbol> /* RFC 2383 reason */),
577 /// Lint level was set by a command-line flag.
581 impl_stable_hash_for!(enum self::LintSource {
583 Node(name, span, reason),
587 pub type LevelSource = (Level, LintSource);
594 pub use self::levels::{LintLevelSets, LintLevelMap};
597 pub struct LintBuffer {
598 map: NodeMap<Vec<BufferedEarlyLint>>,
602 pub fn add_lint(&mut self,
607 diagnostic: BuiltinLintDiagnostics) {
608 let early_lint = BufferedEarlyLint {
609 lint_id: LintId::of(lint),
612 msg: msg.to_string(),
615 let arr = self.map.entry(id).or_default();
616 if !arr.contains(&early_lint) {
617 arr.push(early_lint);
621 pub fn take(&mut self, id: ast::NodeId) -> Vec<BufferedEarlyLint> {
622 self.map.remove(&id).unwrap_or_default()
625 pub fn get_any(&self) -> Option<&[BufferedEarlyLint]> {
626 let key = self.map.keys().next().map(|k| *k);
627 key.map(|k| &self.map[&k][..])
631 pub fn struct_lint_level<'a>(sess: &'a Session,
635 span: Option<MultiSpan>,
637 -> DiagnosticBuilder<'a>
639 let mut err = match (level, span) {
640 (Level::Allow, _) => return sess.diagnostic().struct_dummy(),
641 (Level::Warn, Some(span)) => sess.struct_span_warn(span, msg),
642 (Level::Warn, None) => sess.struct_warn(msg),
643 (Level::Deny, Some(span)) |
644 (Level::Forbid, Some(span)) => sess.struct_span_err(span, msg),
645 (Level::Deny, None) |
646 (Level::Forbid, None) => sess.struct_err(msg),
649 // Check for future incompatibility lints and issue a stronger warning.
650 let lints = sess.lint_store.borrow();
651 let lint_id = LintId::of(lint);
652 let future_incompatible = lints.future_incompatible(lint_id);
654 // If this code originates in a foreign macro, aka something that this crate
655 // did not itself author, then it's likely that there's nothing this crate
656 // can do about it. We probably want to skip the lint entirely.
657 if err.span.primary_spans().iter().any(|s| in_external_macro(sess, *s)) {
658 // Any suggestions made here are likely to be incorrect, so anything we
659 // emit shouldn't be automatically fixed by rustfix.
660 err.allow_suggestions(false);
662 // If this is a future incompatible lint it'll become a hard error, so
663 // we have to emit *something*. Also allow lints to whitelist themselves
664 // on a case-by-case basis for emission in a foreign macro.
665 if future_incompatible.is_none() && !lint.report_in_external_macro {
667 // Don't continue further, since we don't want to have
668 // `diag_span_note_once` called for a diagnostic that isn't emitted.
673 let name = lint.name_lower();
675 LintSource::Default => {
678 DiagnosticMessageId::from(lint),
679 &format!("`#[{}({})]` on by default", level.as_str(), name));
681 LintSource::CommandLine(lint_flag_val) => {
682 let flag = match level {
685 Level::Forbid => "-F",
686 Level::Allow => panic!(),
688 let hyphen_case_lint_name = name.replace("_", "-");
689 if lint_flag_val.as_str() == name {
692 DiagnosticMessageId::from(lint),
693 &format!("requested on the command line with `{} {}`",
694 flag, hyphen_case_lint_name));
696 let hyphen_case_flag_val = lint_flag_val.as_str().replace("_", "-");
699 DiagnosticMessageId::from(lint),
700 &format!("`{} {}` implied by `{} {}`",
701 flag, hyphen_case_lint_name, flag,
702 hyphen_case_flag_val));
705 LintSource::Node(lint_attr_name, src, reason) => {
706 if let Some(rationale) = reason {
707 err.note(&rationale.as_str());
709 sess.diag_span_note_once(&mut err, DiagnosticMessageId::from(lint),
710 src, "lint level defined here");
711 if lint_attr_name.as_str() != name {
712 let level_str = level.as_str();
713 sess.diag_note_once(&mut err, DiagnosticMessageId::from(lint),
714 &format!("`#[{}({})]` implied by `#[{}({})]`",
715 level_str, name, level_str, lint_attr_name));
720 err.code(DiagnosticId::Lint(name));
722 if let Some(future_incompatible) = future_incompatible {
723 const STANDARD_MESSAGE: &str =
724 "this was previously accepted by the compiler but is being phased out; \
725 it will become a hard error";
727 let explanation = if lint_id == LintId::of(builtin::UNSTABLE_NAME_COLLISIONS) {
728 "once this method is added to the standard library, \
729 the ambiguity may cause an error or change in behavior!"
731 } else if lint_id == LintId::of(builtin::MUTABLE_BORROW_RESERVATION_CONFLICT) {
732 "this borrowing pattern was not meant to be accepted, \
733 and may become a hard error in the future"
735 } else if let Some(edition) = future_incompatible.edition {
736 format!("{} in the {} edition!", STANDARD_MESSAGE, edition)
738 format!("{} in a future release!", STANDARD_MESSAGE)
740 let citation = format!("for more information, see {}",
741 future_incompatible.reference);
742 err.warn(&explanation);
749 pub fn maybe_lint_level_root(tcx: TyCtxt<'_>, id: hir::HirId) -> bool {
750 let attrs = tcx.hir().attrs(id);
751 attrs.iter().any(|attr| Level::from_symbol(attr.name_or_empty()).is_some())
754 fn lint_levels(tcx: TyCtxt<'_>, cnum: CrateNum) -> &LintLevelMap {
755 assert_eq!(cnum, LOCAL_CRATE);
756 let mut builder = LintLevelMapBuilder {
757 levels: LintLevelSets::builder(tcx.sess),
760 let krate = tcx.hir().krate();
762 let push = builder.levels.push(&krate.attrs);
763 builder.levels.register_id(hir::CRATE_HIR_ID);
764 for macro_def in &krate.exported_macros {
765 builder.levels.register_id(macro_def.hir_id);
767 intravisit::walk_crate(&mut builder, krate);
768 builder.levels.pop(push);
770 tcx.arena.alloc(builder.levels.build_map())
773 struct LintLevelMapBuilder<'tcx> {
774 levels: levels::LintLevelsBuilder<'tcx>,
778 impl LintLevelMapBuilder<'tcx> {
779 fn with_lint_attrs<F>(&mut self,
781 attrs: &[ast::Attribute],
783 where F: FnOnce(&mut Self)
785 let push = self.levels.push(attrs);
787 self.levels.register_id(id);
790 self.levels.pop(push);
794 impl intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
795 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
796 intravisit::NestedVisitorMap::All(&self.tcx.hir())
799 fn visit_param(&mut self, param: &'tcx hir::Param) {
800 self.with_lint_attrs(param.hir_id, ¶m.attrs, |builder| {
801 intravisit::walk_param(builder, param);
805 fn visit_item(&mut self, it: &'tcx hir::Item) {
806 self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
807 intravisit::walk_item(builder, it);
811 fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem) {
812 self.with_lint_attrs(it.hir_id, &it.attrs, |builder| {
813 intravisit::walk_foreign_item(builder, it);
817 fn visit_expr(&mut self, e: &'tcx hir::Expr) {
818 self.with_lint_attrs(e.hir_id, &e.attrs, |builder| {
819 intravisit::walk_expr(builder, e);
823 fn visit_struct_field(&mut self, s: &'tcx hir::StructField) {
824 self.with_lint_attrs(s.hir_id, &s.attrs, |builder| {
825 intravisit::walk_struct_field(builder, s);
829 fn visit_variant(&mut self,
830 v: &'tcx hir::Variant,
831 g: &'tcx hir::Generics,
832 item_id: hir::HirId) {
833 self.with_lint_attrs(v.id, &v.attrs, |builder| {
834 intravisit::walk_variant(builder, v, g, item_id);
838 fn visit_local(&mut self, l: &'tcx hir::Local) {
839 self.with_lint_attrs(l.hir_id, &l.attrs, |builder| {
840 intravisit::walk_local(builder, l);
844 fn visit_arm(&mut self, a: &'tcx hir::Arm) {
845 self.with_lint_attrs(a.hir_id, &a.attrs, |builder| {
846 intravisit::walk_arm(builder, a);
850 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
851 self.with_lint_attrs(trait_item.hir_id, &trait_item.attrs, |builder| {
852 intravisit::walk_trait_item(builder, trait_item);
856 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
857 self.with_lint_attrs(impl_item.hir_id, &impl_item.attrs, |builder| {
858 intravisit::walk_impl_item(builder, impl_item);
863 pub fn provide(providers: &mut Providers<'_>) {
864 providers.lint_levels = lint_levels;
867 /// Returns whether `span` originates in a foreign crate's external macro.
869 /// This is used to test whether a lint should not even begin to figure out whether it should
870 /// be reported on the current node.
871 pub fn in_external_macro(sess: &Session, span: Span) -> bool {
872 let expn_data = span.ctxt().outer_expn_data();
873 match expn_data.kind {
874 ExpnKind::Root | ExpnKind::Desugaring(DesugaringKind::ForLoop) => false,
875 ExpnKind::AstPass(_) | ExpnKind::Desugaring(_) => true, // well, it's "external"
876 ExpnKind::Macro(MacroKind::Bang, _) => {
877 if expn_data.def_site.is_dummy() {
878 // Dummy span for the `def_site` means it's an external macro.
881 match sess.source_map().span_to_snippet(expn_data.def_site) {
882 Ok(code) => !code.starts_with("macro_rules"),
883 // No snippet means external macro or compiler-builtin expansion.
887 ExpnKind::Macro(..) => true, // definitely a plugin
891 /// Returns `true` if `span` originates in a derive-macro's expansion.
892 pub fn in_derive_expansion(span: Span) -> bool {
893 if let ExpnKind::Macro(MacroKind::Derive, _) = span.ctxt().outer_expn_data().kind {