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::*;
36 use errors::{DiagnosticBuilder, DiagnosticId};
37 use hir::def_id::{CrateNum, LOCAL_CRATE};
38 use hir::intravisit::{self, FnKind};
43 use syntax::codemap::MultiSpan;
44 use syntax::symbol::Symbol;
45 use syntax::visit as ast_visit;
48 use ty::maps::Providers;
49 use util::nodemap::NodeMap;
51 pub use lint::context::{LateContext, EarlyContext, LintContext, LintStore,
52 check_crate, check_ast_crate,
53 FutureIncompatibleInfo, BufferedEarlyLint};
55 /// Specification of a single lint.
56 #[derive(Copy, Clone, Debug)]
58 /// A string identifier for the lint.
60 /// This identifies the lint in attributes and in command-line arguments.
61 /// In those contexts it is always lowercase, but this field is compared
62 /// in a way which is case-insensitive for ASCII characters. This allows
63 /// `declare_lint!()` invocations to follow the convention of upper-case
64 /// statics without repeating the name.
66 /// The name is written with underscores, e.g. "unused_imports".
67 /// On the command line, underscores become dashes.
68 pub name: &'static str,
70 /// Default level for the lint.
71 pub default_level: Level,
73 /// Description of the lint or the issue it detects.
75 /// e.g. "imports that are never used"
76 pub desc: &'static str,
80 /// Get the lint's name, with ASCII letters converted to lowercase.
81 pub fn name_lower(&self) -> String {
82 self.name.to_ascii_lowercase()
86 /// Declare a static item of type `&'static Lint`.
88 macro_rules! declare_lint {
89 ($vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
90 $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
91 name: stringify!($NAME),
92 default_level: $crate::lint::$Level,
98 /// Declare a static `LintArray` and return it as an expression.
100 macro_rules! lint_array { ($( $lint:expr ),*) => (
102 static ARRAY: LintArray = &[ $( &$lint ),* ];
107 pub type LintArray = &'static [&'static &'static Lint];
110 /// Get descriptions of the lints this `LintPass` object can emit.
112 /// NB: there is no enforcement that the object only emits lints it registered.
113 /// And some `rustc` internal `LintPass`es register lints to be emitted by other
114 /// parts of the compiler. If you want enforced access restrictions for your
115 /// `Lint`, make it a private `static` item in its own module.
116 fn get_lints(&self) -> LintArray;
120 /// Trait for types providing lint checks.
122 /// Each `check` method checks a single syntax node, and should not
123 /// invoke methods recursively (unlike `Visitor`). By default they
126 // FIXME: eliminate the duplication with `Visitor`. But this also
127 // contains a few lint-specific methods with no equivalent in `Visitor`.
128 pub trait LateLintPass<'a, 'tcx>: LintPass {
129 fn check_body(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
130 fn check_body_post(&mut self, _: &LateContext, _: &'tcx hir::Body) { }
131 fn check_name(&mut self, _: &LateContext, _: Span, _: ast::Name) { }
132 fn check_crate(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }
133 fn check_crate_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Crate) { }
134 fn check_mod(&mut self,
135 _: &LateContext<'a, 'tcx>,
139 fn check_mod_post(&mut self,
140 _: &LateContext<'a, 'tcx>,
144 fn check_foreign_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ForeignItem) { }
145 fn check_foreign_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ForeignItem) { }
146 fn check_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Item) { }
147 fn check_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Item) { }
148 fn check_local(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Local) { }
149 fn check_block(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Block) { }
150 fn check_block_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Block) { }
151 fn check_stmt(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Stmt) { }
152 fn check_arm(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Arm) { }
153 fn check_pat(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Pat) { }
154 fn check_decl(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Decl) { }
155 fn check_expr(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Expr) { }
156 fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Expr) { }
157 fn check_ty(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Ty) { }
158 fn check_generics(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Generics) { }
159 fn check_fn(&mut self,
160 _: &LateContext<'a, 'tcx>,
162 _: &'tcx hir::FnDecl,
166 fn check_fn_post(&mut self,
167 _: &LateContext<'a, 'tcx>,
169 _: &'tcx hir::FnDecl,
173 fn check_trait_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::TraitItem) { }
174 fn check_trait_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::TraitItem) { }
175 fn check_impl_item(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ImplItem) { }
176 fn check_impl_item_post(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::ImplItem) { }
177 fn check_struct_def(&mut self,
178 _: &LateContext<'a, 'tcx>,
179 _: &'tcx hir::VariantData,
181 _: &'tcx hir::Generics,
183 fn check_struct_def_post(&mut self,
184 _: &LateContext<'a, 'tcx>,
185 _: &'tcx hir::VariantData,
187 _: &'tcx hir::Generics,
189 fn check_struct_field(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::StructField) { }
190 fn check_variant(&mut self,
191 _: &LateContext<'a, 'tcx>,
192 _: &'tcx hir::Variant,
193 _: &'tcx hir::Generics) { }
194 fn check_variant_post(&mut self,
195 _: &LateContext<'a, 'tcx>,
196 _: &'tcx hir::Variant,
197 _: &'tcx hir::Generics) { }
198 fn check_lifetime(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Lifetime) { }
199 fn check_lifetime_def(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::LifetimeDef) { }
200 fn check_path(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx hir::Path, _: ast::NodeId) { }
201 fn check_attribute(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx ast::Attribute) { }
203 /// Called when entering a syntax node that can have lint attributes such
204 /// as `#[allow(...)]`. Called with *all* the attributes of that node.
205 fn enter_lint_attrs(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx [ast::Attribute]) { }
207 /// Counterpart to `enter_lint_attrs`.
208 fn exit_lint_attrs(&mut self, _: &LateContext<'a, 'tcx>, _: &'tcx [ast::Attribute]) { }
211 pub trait EarlyLintPass: LintPass {
212 fn check_ident(&mut self, _: &EarlyContext, _: Span, _: ast::Ident) { }
213 fn check_crate(&mut self, _: &EarlyContext, _: &ast::Crate) { }
214 fn check_crate_post(&mut self, _: &EarlyContext, _: &ast::Crate) { }
215 fn check_mod(&mut self, _: &EarlyContext, _: &ast::Mod, _: Span, _: ast::NodeId) { }
216 fn check_mod_post(&mut self, _: &EarlyContext, _: &ast::Mod, _: Span, _: ast::NodeId) { }
217 fn check_foreign_item(&mut self, _: &EarlyContext, _: &ast::ForeignItem) { }
218 fn check_foreign_item_post(&mut self, _: &EarlyContext, _: &ast::ForeignItem) { }
219 fn check_item(&mut self, _: &EarlyContext, _: &ast::Item) { }
220 fn check_item_post(&mut self, _: &EarlyContext, _: &ast::Item) { }
221 fn check_local(&mut self, _: &EarlyContext, _: &ast::Local) { }
222 fn check_block(&mut self, _: &EarlyContext, _: &ast::Block) { }
223 fn check_block_post(&mut self, _: &EarlyContext, _: &ast::Block) { }
224 fn check_stmt(&mut self, _: &EarlyContext, _: &ast::Stmt) { }
225 fn check_arm(&mut self, _: &EarlyContext, _: &ast::Arm) { }
226 fn check_pat(&mut self, _: &EarlyContext, _: &ast::Pat) { }
227 fn check_expr(&mut self, _: &EarlyContext, _: &ast::Expr) { }
228 fn check_expr_post(&mut self, _: &EarlyContext, _: &ast::Expr) { }
229 fn check_ty(&mut self, _: &EarlyContext, _: &ast::Ty) { }
230 fn check_generics(&mut self, _: &EarlyContext, _: &ast::Generics) { }
231 fn check_fn(&mut self, _: &EarlyContext,
232 _: ast_visit::FnKind, _: &ast::FnDecl, _: Span, _: ast::NodeId) { }
233 fn check_fn_post(&mut self, _: &EarlyContext,
234 _: ast_visit::FnKind, _: &ast::FnDecl, _: Span, _: ast::NodeId) { }
235 fn check_trait_item(&mut self, _: &EarlyContext, _: &ast::TraitItem) { }
236 fn check_trait_item_post(&mut self, _: &EarlyContext, _: &ast::TraitItem) { }
237 fn check_impl_item(&mut self, _: &EarlyContext, _: &ast::ImplItem) { }
238 fn check_impl_item_post(&mut self, _: &EarlyContext, _: &ast::ImplItem) { }
239 fn check_struct_def(&mut self, _: &EarlyContext,
240 _: &ast::VariantData, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
241 fn check_struct_def_post(&mut self, _: &EarlyContext,
242 _: &ast::VariantData, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
243 fn check_struct_field(&mut self, _: &EarlyContext, _: &ast::StructField) { }
244 fn check_variant(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
245 fn check_variant_post(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
246 fn check_lifetime(&mut self, _: &EarlyContext, _: &ast::Lifetime) { }
247 fn check_lifetime_def(&mut self, _: &EarlyContext, _: &ast::LifetimeDef) { }
248 fn check_path(&mut self, _: &EarlyContext, _: &ast::Path, _: ast::NodeId) { }
249 fn check_path_list_item(&mut self, _: &EarlyContext, _: &ast::PathListItem) { }
250 fn check_attribute(&mut self, _: &EarlyContext, _: &ast::Attribute) { }
252 /// Called when entering a syntax node that can have lint attributes such
253 /// as `#[allow(...)]`. Called with *all* the attributes of that node.
254 fn enter_lint_attrs(&mut self, _: &EarlyContext, _: &[ast::Attribute]) { }
256 /// Counterpart to `enter_lint_attrs`.
257 fn exit_lint_attrs(&mut self, _: &EarlyContext, _: &[ast::Attribute]) { }
260 /// A lint pass boxed up as a trait object.
261 pub type EarlyLintPassObject = Box<EarlyLintPass + 'static>;
262 pub type LateLintPassObject = Box<for<'a, 'tcx> LateLintPass<'a, 'tcx> + 'static>;
264 /// Identifies a lint known to the compiler.
265 #[derive(Clone, Copy, Debug)]
267 // Identity is based on pointer equality of this field.
271 impl PartialEq for LintId {
272 fn eq(&self, other: &LintId) -> bool {
273 (self.lint as *const Lint) == (other.lint as *const Lint)
277 impl Eq for LintId { }
279 impl hash::Hash for LintId {
280 fn hash<H: hash::Hasher>(&self, state: &mut H) {
281 let ptr = self.lint as *const Lint;
287 /// Get the `LintId` for a `Lint`.
288 pub fn of(lint: &'static Lint) -> LintId {
294 pub fn lint_name_raw(&self) -> &'static str {
298 /// Get the name of the lint.
299 pub fn to_string(&self) -> String {
300 self.lint.name_lower()
304 /// Setting for how to handle a lint.
305 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
307 Allow, Warn, Deny, Forbid
310 impl_stable_hash_for!(enum self::Level {
318 /// Convert a level to a lower-case string.
319 pub fn as_str(self) -> &'static str {
328 /// Convert a lower-case string to a level.
329 pub fn from_str(x: &str) -> Option<Level> {
331 "allow" => Some(Allow),
332 "warn" => Some(Warn),
333 "deny" => Some(Deny),
334 "forbid" => Some(Forbid),
340 /// How a lint level was set.
341 #[derive(Clone, Copy, PartialEq, Eq)]
342 pub enum LintSource {
343 /// Lint is at the default level as declared
344 /// in rustc or a plugin.
347 /// Lint level was set by an attribute.
348 Node(ast::Name, Span),
350 /// Lint level was set by a command-line flag.
354 impl_stable_hash_for!(enum self::LintSource {
360 pub type LevelSource = (Level, LintSource);
366 pub use self::levels::{LintLevelSets, LintLevelMap};
368 pub struct LintBuffer {
369 map: NodeMap<Vec<BufferedEarlyLint>>,
373 pub fn new() -> LintBuffer {
374 LintBuffer { map: NodeMap() }
377 pub fn add_lint(&mut self,
382 let early_lint = BufferedEarlyLint {
383 lint_id: LintId::of(lint),
386 msg: msg.to_string(),
388 let arr = self.map.entry(id).or_insert(Vec::new());
389 if !arr.contains(&early_lint) {
390 arr.push(early_lint);
394 pub fn take(&mut self, id: ast::NodeId) -> Vec<BufferedEarlyLint> {
395 self.map.remove(&id).unwrap_or(Vec::new())
398 pub fn get_any(&self) -> Option<&[BufferedEarlyLint]> {
399 let key = self.map.keys().next().map(|k| *k);
400 key.map(|k| &self.map[&k][..])
404 pub fn struct_lint_level<'a>(sess: &'a Session,
408 span: Option<MultiSpan>,
410 -> DiagnosticBuilder<'a>
412 let mut err = match (level, span) {
413 (Level::Allow, _) => return sess.diagnostic().struct_dummy(),
414 (Level::Warn, Some(span)) => sess.struct_span_warn(span, msg),
415 (Level::Warn, None) => sess.struct_warn(msg),
416 (Level::Deny, Some(span)) |
417 (Level::Forbid, Some(span)) => sess.struct_span_err(span, msg),
418 (Level::Deny, None) |
419 (Level::Forbid, None) => sess.struct_err(msg),
422 let name = lint.name_lower();
424 LintSource::Default => {
428 &format!("#[{}({})] on by default", level.as_str(), name));
430 LintSource::CommandLine(lint_flag_val) => {
431 let flag = match level {
434 Level::Forbid => "-F",
435 Level::Allow => panic!(),
437 let hyphen_case_lint_name = name.replace("_", "-");
438 if lint_flag_val.as_str() == name {
442 &format!("requested on the command line with `{} {}`",
443 flag, hyphen_case_lint_name));
445 let hyphen_case_flag_val = lint_flag_val.as_str().replace("_", "-");
449 &format!("`{} {}` implied by `{} {}`",
450 flag, hyphen_case_lint_name, flag,
451 hyphen_case_flag_val));
454 LintSource::Node(lint_attr_name, src) => {
455 sess.diag_span_note_once(&mut err, lint, src, "lint level defined here");
456 if lint_attr_name.as_str() != name {
457 let level_str = level.as_str();
458 sess.diag_note_once(&mut err, lint,
459 &format!("#[{}({})] implied by #[{}({})]",
460 level_str, name, level_str, lint_attr_name));
465 err.code(DiagnosticId::Lint(name));
467 // Check for future incompatibility lints and issue a stronger warning.
468 let lints = sess.lint_store.borrow();
469 if let Some(future_incompatible) = lints.future_incompatible(LintId::of(lint)) {
470 let explanation = format!("this was previously accepted by the compiler \
471 but is being phased out; \
472 it will become a hard error in a future release!");
473 let citation = format!("for more information, see {}",
474 future_incompatible.reference);
475 err.warn(&explanation);
482 fn lint_levels<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, cnum: CrateNum)
485 assert_eq!(cnum, LOCAL_CRATE);
486 let mut builder = LintLevelMapBuilder {
487 levels: LintLevelSets::builder(tcx.sess),
490 let krate = tcx.hir.krate();
492 builder.with_lint_attrs(ast::CRATE_NODE_ID, &krate.attrs, |builder| {
493 intravisit::walk_crate(builder, krate);
496 Rc::new(builder.levels.build_map())
499 struct LintLevelMapBuilder<'a, 'tcx: 'a> {
500 levels: levels::LintLevelsBuilder<'tcx>,
501 tcx: TyCtxt<'a, 'tcx, 'tcx>,
504 impl<'a, 'tcx> LintLevelMapBuilder<'a, 'tcx> {
505 fn with_lint_attrs<F>(&mut self,
507 attrs: &[ast::Attribute],
509 where F: FnOnce(&mut Self)
511 let push = self.levels.push(attrs);
512 self.levels.register_id(self.tcx.hir.definitions().node_to_hir_id(id));
514 self.levels.pop(push);
518 impl<'a, 'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'a, 'tcx> {
519 fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
520 intravisit::NestedVisitorMap::All(&self.tcx.hir)
523 fn visit_item(&mut self, it: &'tcx hir::Item) {
524 self.with_lint_attrs(it.id, &it.attrs, |builder| {
525 intravisit::walk_item(builder, it);
529 fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem) {
530 self.with_lint_attrs(it.id, &it.attrs, |builder| {
531 intravisit::walk_foreign_item(builder, it);
535 fn visit_expr(&mut self, e: &'tcx hir::Expr) {
536 self.with_lint_attrs(e.id, &e.attrs, |builder| {
537 intravisit::walk_expr(builder, e);
541 fn visit_struct_field(&mut self, s: &'tcx hir::StructField) {
542 self.with_lint_attrs(s.id, &s.attrs, |builder| {
543 intravisit::walk_struct_field(builder, s);
547 fn visit_variant(&mut self,
548 v: &'tcx hir::Variant,
549 g: &'tcx hir::Generics,
550 item_id: ast::NodeId) {
551 self.with_lint_attrs(v.node.data.id(), &v.node.attrs, |builder| {
552 intravisit::walk_variant(builder, v, g, item_id);
556 fn visit_local(&mut self, l: &'tcx hir::Local) {
557 self.with_lint_attrs(l.id, &l.attrs, |builder| {
558 intravisit::walk_local(builder, l);
562 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
563 self.with_lint_attrs(trait_item.id, &trait_item.attrs, |builder| {
564 intravisit::walk_trait_item(builder, trait_item);
568 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
569 self.with_lint_attrs(impl_item.id, &impl_item.attrs, |builder| {
570 intravisit::walk_impl_item(builder, impl_item);
575 pub fn provide(providers: &mut Providers) {
576 providers.lint_levels = lint_levels;