1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Lints, aka compiler warnings.
13 //! A 'lint' check is a kind of miscellaneous constraint that a user _might_
14 //! want to enforce, but might reasonably want to permit as well, on a
15 //! module-by-module basis. They contrast with static constraints enforced by
16 //! other phases of the compiler, which are generally required to hold in order
17 //! to compile the program at all.
19 //! Most lints can be written as `LintPass` instances. These run just before
20 //! translation to LLVM bytecode. The `LintPass`es built into rustc are defined
21 //! within `builtin.rs`, which has further comments on how to add such a lint.
22 //! rustc can also load user-defined lint plugins via the plugin mechanism.
24 //! Some of rustc's lints are defined elsewhere in the compiler and work by
25 //! calling `add_lint()` on the overall `Session` object. This works when
26 //! it happens before the main lint pass, which emits the lints stored by
27 //! `add_lint()`. To emit lints after the main lint pass (from trans, for
28 //! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
31 pub use self::Level::*;
32 pub use self::LintSource::*;
34 use rustc_data_structures::sync::Lrc;
36 use errors::{DiagnosticBuilder, DiagnosticId};
37 use hir::def_id::{CrateNum, LOCAL_CRATE};
38 use hir::intravisit::{self, FnKind};
40 use lint::builtin::BuiltinLintDiagnostics;
41 use session::{Session, DiagnosticMessageId};
44 use syntax::codemap::MultiSpan;
45 use syntax::edition::Edition;
46 use syntax::symbol::Symbol;
47 use syntax::visit as ast_visit;
50 use ty::maps::Providers;
51 use util::nodemap::NodeMap;
53 pub use lint::context::{LateContext, EarlyContext, LintContext, LintStore,
54 check_crate, check_ast_crate,
55 FutureIncompatibleInfo, BufferedEarlyLint};
57 /// Specification of a single lint.
58 #[derive(Copy, Clone, Debug)]
60 /// A string identifier for the lint.
62 /// This identifies the lint in attributes and in command-line arguments.
63 /// In those contexts it is always lowercase, but this field is compared
64 /// in a way which is case-insensitive for ASCII characters. This allows
65 /// `declare_lint!()` invocations to follow the convention of upper-case
66 /// statics without repeating the name.
68 /// The name is written with underscores, e.g. "unused_imports".
69 /// On the command line, underscores become dashes.
70 pub name: &'static str,
72 /// Default level for the lint.
73 pub default_level: Level,
75 /// Description of the lint or the issue it detects.
77 /// e.g. "imports that are never used"
78 pub desc: &'static str,
80 /// Deny lint after this edition
81 pub edition_deny: Option<Edition>,
85 /// Get the lint's name, with ASCII letters converted to lowercase.
86 pub fn name_lower(&self) -> String {
87 self.name.to_ascii_lowercase()
90 pub fn default_level(&self, session: &Session) -> Level {
91 if let Some(edition_deny) = self.edition_deny {
92 if session.edition() >= edition_deny {
100 /// Declare a static item of type `&'static Lint`.
102 macro_rules! declare_lint {
103 ($vis: vis $NAME: ident, $Level: ident, $desc: expr, $edition: expr) => (
104 $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
105 name: stringify!($NAME),
106 default_level: $crate::lint::$Level,
108 edition_deny: Some($edition)
111 ($vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
112 $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
113 name: stringify!($NAME),
114 default_level: $crate::lint::$Level,
121 /// Declare a static `LintArray` and return it as an expression.
123 macro_rules! lint_array {
124 ($( $lint:expr ),*,) => { lint_array!( $( $lint ),* ) };
125 ($( $lint:expr ),*) => {{
126 static ARRAY: LintArray = &[ $( &$lint ),* ];
131 pub type LintArray = &'static [&'static &'static Lint];
134 /// Get descriptions of the lints this `LintPass` object can emit.
136 /// NB: there is no enforcement that the object only emits lints it registered.
137 /// And some `rustc` internal `LintPass`es register lints to be emitted by other
138 /// parts of the compiler. If you want enforced access restrictions for your
139 /// `Lint`, make it a private `static` item in its own module.
140 fn get_lints(&self) -> LintArray;
144 /// Trait for types providing lint checks.
146 /// Each `check` method checks a single syntax node, and should not
147 /// invoke methods recursively (unlike `Visitor`). By default they
150 // FIXME: eliminate the duplication with `Visitor`. But this also
151 // contains a few lint-specific methods with no equivalent in `Visitor`.
152 pub trait LateLintPass<'a, 'tcx>: LintPass {
153 fn check_body(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
154 fn check_body_post(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
155 fn check_name(&mut self, _: &LateContext, _: Span, _: ast::Name) { }
156 fn check_crate(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }
157 fn check_crate_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }
158 fn check_mod(&mut self,
159 _: &LateContext<'a, 'tcx>,
163 fn check_mod_post(&mut self,
164 _: &LateContext<'a, 'tcx>,
168 fn check_foreign_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ForeignItem) { }
169 fn check_foreign_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ForeignItem) { }
170 fn check_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Item) { }
171 fn check_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Item) { }
172 fn check_local(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Local) { }
173 fn check_block(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Block) { }
174 fn check_block_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Block) { }
175 fn check_stmt(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Stmt) { }
176 fn check_arm(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Arm) { }
177 fn check_pat(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Pat) { }
178 fn check_decl(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Decl) { }
179 fn check_expr(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Expr) { }
180 fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Expr) { }
181 fn check_ty(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Ty) { }
182 fn check_generic_param(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::GenericParam) { }
183 fn check_generics(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Generics) { }
184 fn check_where_predicate(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::WherePredicate) { }
185 fn check_poly_trait_ref(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::PolyTraitRef,
186 _: hir::TraitBoundModifier) { }
187 fn check_fn(&mut self,
188 _: &LateContext<'a, 'tcx>,
190 _: &'tcx hir::FnDecl,
194 fn check_fn_post(&mut self,
195 _: &LateContext<'a, 'tcx>,
197 _: &'tcx hir::FnDecl,
201 fn check_trait_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::TraitItem) { }
202 fn check_trait_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::TraitItem) { }
203 fn check_impl_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ImplItem) { }
204 fn check_impl_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ImplItem) { }
205 fn check_struct_def(&mut self,
206 _: &LateContext<'a, 'tcx>,
207 _: &'tcx hir::VariantData,
209 _: &'tcx hir::Generics,
211 fn check_struct_def_post(&mut self,
212 _: &LateContext<'a, 'tcx>,
213 _: &'tcx hir::VariantData,
215 _: &'tcx hir::Generics,
217 fn check_struct_field(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::StructField) { }
218 fn check_variant(&mut self,
219 _: &LateContext<'a, 'tcx>,
220 _: &'tcx hir::Variant,
221 _: &'tcx hir::Generics) { }
222 fn check_variant_post(&mut self,
223 _: &LateContext<'a, 'tcx>,
224 _: &'tcx hir::Variant,
225 _: &'tcx hir::Generics) { }
226 fn check_lifetime(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Lifetime) { }
227 fn check_path(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Path, _: ast::NodeId) { }
228 fn check_attribute(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx ast::Attribute) { }
230 /// Called when entering a syntax node that can have lint attributes such
231 /// as `#[allow(...)]`. Called with *all* the attributes of that node.
232 fn enter_lint_attrs(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx [ast::Attribute]) { }
234 /// Counterpart to `enter_lint_attrs`.
235 fn exit_lint_attrs(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx [ast::Attribute]) { }
238 pub trait EarlyLintPass: LintPass {
239 fn check_ident(&mut self, _: &EarlyContext, _: Span, _: ast::Ident) { }
240 fn check_crate(&mut self, _: &EarlyContext, _: &ast::Crate) { }
241 fn check_crate_post(&mut self, _: &EarlyContext, _: &ast::Crate) { }
242 fn check_mod(&mut self, _: &EarlyContext, _: &ast::Mod, _: Span, _: ast::NodeId) { }
243 fn check_mod_post(&mut self, _: &EarlyContext, _: &ast::Mod, _: Span, _: ast::NodeId) { }
244 fn check_foreign_item(&mut self, _: &EarlyContext, _: &ast::ForeignItem) { }
245 fn check_foreign_item_post(&mut self, _: &EarlyContext, _: &ast::ForeignItem) { }
246 fn check_item(&mut self, _: &EarlyContext, _: &ast::Item) { }
247 fn check_item_post(&mut self, _: &EarlyContext, _: &ast::Item) { }
248 fn check_local(&mut self, _: &EarlyContext, _: &ast::Local) { }
249 fn check_block(&mut self, _: &EarlyContext, _: &ast::Block) { }
250 fn check_block_post(&mut self, _: &EarlyContext, _: &ast::Block) { }
251 fn check_stmt(&mut self, _: &EarlyContext, _: &ast::Stmt) { }
252 fn check_arm(&mut self, _: &EarlyContext, _: &ast::Arm) { }
253 fn check_pat(&mut self, _: &EarlyContext, _: &ast::Pat) { }
254 fn check_expr(&mut self, _: &EarlyContext, _: &ast::Expr) { }
255 fn check_expr_post(&mut self, _: &EarlyContext, _: &ast::Expr) { }
256 fn check_ty(&mut self, _: &EarlyContext, _: &ast::Ty) { }
257 fn check_generic_param(&mut self, _: &EarlyContext, _: &ast::GenericParam) { }
258 fn check_generics(&mut self, _: &EarlyContext, _: &ast::Generics) { }
259 fn check_where_predicate(&mut self, _: &EarlyContext, _: &ast::WherePredicate) { }
260 fn check_poly_trait_ref(&mut self, _: &EarlyContext, _: &ast::PolyTraitRef,
261 _: &ast::TraitBoundModifier) { }
262 fn check_fn(&mut self, _: &EarlyContext,
263 _: ast_visit::FnKind, _: &ast::FnDecl, _: Span, _: ast::NodeId) { }
264 fn check_fn_post(&mut self, _: &EarlyContext,
265 _: ast_visit::FnKind, _: &ast::FnDecl, _: Span, _: ast::NodeId) { }
266 fn check_trait_item(&mut self, _: &EarlyContext, _: &ast::TraitItem) { }
267 fn check_trait_item_post(&mut self, _: &EarlyContext, _: &ast::TraitItem) { }
268 fn check_impl_item(&mut self, _: &EarlyContext, _: &ast::ImplItem) { }
269 fn check_impl_item_post(&mut self, _: &EarlyContext, _: &ast::ImplItem) { }
270 fn check_struct_def(&mut self, _: &EarlyContext,
271 _: &ast::VariantData, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
272 fn check_struct_def_post(&mut self, _: &EarlyContext,
273 _: &ast::VariantData, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
274 fn check_struct_field(&mut self, _: &EarlyContext, _: &ast::StructField) { }
275 fn check_variant(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
276 fn check_variant_post(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
277 fn check_lifetime(&mut self, _: &EarlyContext, _: &ast::Lifetime) { }
278 fn check_path(&mut self, _: &EarlyContext, _: &ast::Path, _: ast::NodeId) { }
279 fn check_attribute(&mut self, _: &EarlyContext, _: &ast::Attribute) { }
281 /// Called when entering a syntax node that can have lint attributes such
282 /// as `#[allow(...)]`. Called with *all* the attributes of that node.
283 fn enter_lint_attrs(&mut self, _: &EarlyContext, _: &[ast::Attribute]) { }
285 /// Counterpart to `enter_lint_attrs`.
286 fn exit_lint_attrs(&mut self, _: &EarlyContext, _: &[ast::Attribute]) { }
289 /// A lint pass boxed up as a trait object.
290 pub type EarlyLintPassObject = Box<dyn EarlyLintPass + 'static>;
291 pub type LateLintPassObject = Box<dyn for<'a, 'tcx> LateLintPass<'a, 'tcx> + 'static>;
293 /// Identifies a lint known to the compiler.
294 #[derive(Clone, Copy, Debug)]
296 // Identity is based on pointer equality of this field.
300 impl PartialEq for LintId {
301 fn eq(&self, other: &LintId) -> bool {
302 (self.lint as *const Lint) == (other.lint as *const Lint)
306 impl Eq for LintId { }
308 impl hash::Hash for LintId {
309 fn hash<H: hash::Hasher>(&self, state: &mut H) {
310 let ptr = self.lint as *const Lint;
316 /// Get the `LintId` for a `Lint`.
317 pub fn of(lint: &'static Lint) -> LintId {
323 pub fn lint_name_raw(&self) -> &'static str {
327 /// Get the name of the lint.
328 pub fn to_string(&self) -> String {
329 self.lint.name_lower()
333 /// Setting for how to handle a lint.
334 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
336 Allow, Warn, Deny, Forbid,
339 impl_stable_hash_for!(enum self::Level {
347 /// Convert a level to a lower-case string.
348 pub fn as_str(self) -> &'static str {
357 /// Convert a lower-case string to a level.
358 pub fn from_str(x: &str) -> Option<Level> {
360 "allow" => Some(Allow),
361 "warn" => Some(Warn),
362 "deny" => Some(Deny),
363 "forbid" => Some(Forbid),
369 /// How a lint level was set.
370 #[derive(Clone, Copy, PartialEq, Eq)]
371 pub enum LintSource {
372 /// Lint is at the default level as declared
373 /// in rustc or a plugin.
376 /// Lint level was set by an attribute.
377 Node(ast::Name, Span),
379 /// Lint level was set by a command-line flag.
383 impl_stable_hash_for!(enum self::LintSource {
389 pub type LevelSource = (Level, LintSource);
395 pub use self::levels::{LintLevelSets, LintLevelMap};
397 pub struct LintBuffer {
398 map: NodeMap<Vec<BufferedEarlyLint>>,
402 pub fn new() -> LintBuffer {
403 LintBuffer { map: NodeMap() }
406 pub fn add_lint(&mut self,
411 diagnostic: BuiltinLintDiagnostics) {
412 let early_lint = BufferedEarlyLint {
413 lint_id: LintId::of(lint),
416 msg: msg.to_string(),
419 let arr = self.map.entry(id).or_insert(Vec::new());
420 if !arr.contains(&early_lint) {
421 arr.push(early_lint);
425 pub fn take(&mut self, id: ast::NodeId) -> Vec<BufferedEarlyLint> {
426 self.map.remove(&id).unwrap_or(Vec::new())
429 pub fn get_any(&self) -> Option<&[BufferedEarlyLint]> {
430 let key = self.map.keys().next().map(|k| *k);
431 key.map(|k| &self.map[&k][..])
435 pub fn struct_lint_level<'a>(sess: &'a Session,
439 span: Option<MultiSpan>,
441 -> DiagnosticBuilder<'a>
443 let mut err = match (level, span) {
444 (Level::Allow, _) => return sess.diagnostic().struct_dummy(),
445 (Level::Warn, Some(span)) => sess.struct_span_warn(span, msg),
446 (Level::Warn, None) => sess.struct_warn(msg),
447 (Level::Deny, Some(span)) |
448 (Level::Forbid, Some(span)) => sess.struct_span_err(span, msg),
449 (Level::Deny, None) |
450 (Level::Forbid, None) => sess.struct_err(msg),
453 let name = lint.name_lower();
455 LintSource::Default => {
458 DiagnosticMessageId::from(lint),
459 &format!("#[{}({})] on by default", level.as_str(), name));
461 LintSource::CommandLine(lint_flag_val) => {
462 let flag = match level {
465 Level::Forbid => "-F",
466 Level::Allow => panic!(),
468 let hyphen_case_lint_name = name.replace("_", "-");
469 if lint_flag_val.as_str() == name {
472 DiagnosticMessageId::from(lint),
473 &format!("requested on the command line with `{} {}`",
474 flag, hyphen_case_lint_name));
476 let hyphen_case_flag_val = lint_flag_val.as_str().replace("_", "-");
479 DiagnosticMessageId::from(lint),
480 &format!("`{} {}` implied by `{} {}`",
481 flag, hyphen_case_lint_name, flag,
482 hyphen_case_flag_val));
485 LintSource::Node(lint_attr_name, src) => {
486 sess.diag_span_note_once(&mut err, DiagnosticMessageId::from(lint),
487 src, "lint level defined here");
488 if lint_attr_name.as_str() != name {
489 let level_str = level.as_str();
490 sess.diag_note_once(&mut err, DiagnosticMessageId::from(lint),
491 &format!("#[{}({})] implied by #[{}({})]",
492 level_str, name, level_str, lint_attr_name));
497 err.code(DiagnosticId::Lint(name));
499 // Check for future incompatibility lints and issue a stronger warning.
500 let lints = sess.lint_store.borrow();
501 if let Some(future_incompatible) = lints.future_incompatible(LintId::of(lint)) {
502 let future = if let Some(edition) = future_incompatible.edition {
503 format!("the {} edition", edition)
505 "a future release".to_owned()
507 let explanation = format!("this was previously accepted by the compiler \
508 but is being phased out; \
509 it will become a hard error in {}!", future);
510 let citation = format!("for more information, see {}",
511 future_incompatible.reference);
512 err.warn(&explanation);
519 fn lint_levels<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, cnum: CrateNum)
522 assert_eq!(cnum, LOCAL_CRATE);
523 let mut builder = LintLevelMapBuilder {
524 levels: LintLevelSets::builder(tcx.sess),
527 let krate = tcx.hir.krate();
529 builder.with_lint_attrs(ast::CRATE_NODE_ID, &krate.attrs, |builder| {
530 intravisit::walk_crate(builder, krate);
533 Lrc::new(builder.levels.build_map())
536 struct LintLevelMapBuilder<'a, 'tcx: 'a> {
537 levels: levels::LintLevelsBuilder<'tcx>,
538 tcx: TyCtxt<'a, 'tcx, 'tcx>,
541 impl<'a, 'tcx> LintLevelMapBuilder<'a, 'tcx> {
542 fn with_lint_attrs<F>(&mut self,
544 attrs: &[ast::Attribute],
546 where F: FnOnce(&mut Self)
548 let push = self.levels.push(attrs);
549 self.levels.register_id(self.tcx.hir.definitions().node_to_hir_id(id));
551 self.levels.pop(push);
555 impl<'a, 'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'a, 'tcx> {
556 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
557 intravisit::NestedVisitorMap::All(&self.tcx.hir)
560 fn visit_item(&mut self, it: &'tcx hir::Item) {
561 self.with_lint_attrs(it.id, &it.attrs, |builder| {
562 intravisit::walk_item(builder, it);
566 fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem) {
567 self.with_lint_attrs(it.id, &it.attrs, |builder| {
568 intravisit::walk_foreign_item(builder, it);
572 fn visit_expr(&mut self, e: &'tcx hir::Expr) {
573 self.with_lint_attrs(e.id, &e.attrs, |builder| {
574 intravisit::walk_expr(builder, e);
578 fn visit_struct_field(&mut self, s: &'tcx hir::StructField) {
579 self.with_lint_attrs(s.id, &s.attrs, |builder| {
580 intravisit::walk_struct_field(builder, s);
584 fn visit_variant(&mut self,
585 v: &'tcx hir::Variant,
586 g: &'tcx hir::Generics,
587 item_id: ast::NodeId) {
588 self.with_lint_attrs(v.node.data.id(), &v.node.attrs, |builder| {
589 intravisit::walk_variant(builder, v, g, item_id);
593 fn visit_local(&mut self, l: &'tcx hir::Local) {
594 self.with_lint_attrs(l.id, &l.attrs, |builder| {
595 intravisit::walk_local(builder, l);
599 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
600 self.with_lint_attrs(trait_item.id, &trait_item.attrs, |builder| {
601 intravisit::walk_trait_item(builder, trait_item);
605 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
606 self.with_lint_attrs(impl_item.id, &impl_item.attrs, |builder| {
607 intravisit::walk_impl_item(builder, impl_item);
612 pub fn provide(providers: &mut Providers) {
613 providers.lint_levels = lint_levels;