1 //! Implementation of lint checking.
3 //! The lint checking is mostly consolidated into one pass which runs
4 //! after all other analyses. Throughout compilation, lint warnings
5 //! can be added via the `add_lint` method on the Session structure. This
6 //! requires a span and an ID of the node that the lint is being added to. The
7 //! lint isn't actually emitted at that time because it is unknown what the
8 //! actual lint level at that location is.
10 //! To actually emit lint warnings/errors, a separate pass is used.
11 //! A context keeps track of the current state of all lint levels.
12 //! Upon entering a node of the ast which can modify the lint settings, the
13 //! previous lint state is pushed onto a stack and the ast is then recursed
14 //! upon. As the ast is traversed, this keeps track of the current lint level
15 //! for all lint attributes.
17 use crate::{passes::LateLintPassObject, LateContext, LateLintPass, LintStore};
19 use rustc_data_structures::sync::join;
21 use rustc_hir::def_id::LocalDefId;
22 use rustc_hir::intravisit as hir_visit;
23 use rustc_hir::intravisit::Visitor;
24 use rustc_middle::hir::nested_filter;
25 use rustc_middle::ty::{self, TyCtxt};
26 use rustc_session::lint::LintPass;
27 use rustc_span::symbol::Symbol;
35 /// Extract the `LintStore` from the query context.
36 /// This function exists because we've erased `LintStore` as `dyn Any` in the context.
37 pub fn unerased_lint_store(tcx: TyCtxt<'_>) -> &LintStore {
38 let store: &dyn Any = &*tcx.lint_store;
39 store.downcast_ref().unwrap()
42 macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
43 $cx.pass.$f(&$cx.context, $($args),*);
46 struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
47 context: LateContext<'tcx>,
51 impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'tcx, T> {
52 /// Merge the lints specified by any lint attributes into the
53 /// current lint context, call the provided function, then reset the
54 /// lints in effect to their previous state.
55 fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
59 let attrs = self.context.tcx.hir().attrs(id);
60 let prev = self.context.last_node_with_lint_attrs;
61 self.context.last_node_with_lint_attrs = id;
62 debug!("late context: enter_attrs({:?})", attrs);
63 lint_callback!(self, enter_lint_attrs, attrs);
65 debug!("late context: exit_attrs({:?})", attrs);
66 lint_callback!(self, exit_lint_attrs, attrs);
67 self.context.last_node_with_lint_attrs = prev;
70 fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
74 let old_param_env = self.context.param_env;
75 self.context.param_env =
76 self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
78 self.context.param_env = old_param_env;
81 fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
82 lint_callback!(self, check_mod, m, s, n);
83 hir_visit::walk_mod(self, m, n);
87 impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPass<'tcx, T> {
88 type NestedFilter = nested_filter::All;
90 /// Because lints are scoped lexically, we want to walk nested
91 /// items in the context of the outer item, so enable
93 fn nested_visit_map(&mut self) -> Self::Map {
94 self.context.tcx.hir()
97 fn visit_nested_body(&mut self, body_id: hir::BodyId) {
98 let old_enclosing_body = self.context.enclosing_body.replace(body_id);
99 let old_cached_typeck_results = self.context.cached_typeck_results.get();
101 // HACK(eddyb) avoid trashing `cached_typeck_results` when we're
102 // nested in `visit_fn`, which may have already resulted in them
104 if old_enclosing_body != Some(body_id) {
105 self.context.cached_typeck_results.set(None);
108 let body = self.context.tcx.hir().body(body_id);
109 self.visit_body(body);
110 self.context.enclosing_body = old_enclosing_body;
112 // See HACK comment above.
113 if old_enclosing_body != Some(body_id) {
114 self.context.cached_typeck_results.set(old_cached_typeck_results);
118 fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
119 self.with_lint_attrs(param.hir_id, |cx| {
120 hir_visit::walk_param(cx, param);
124 fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
125 lint_callback!(self, check_body, body);
126 hir_visit::walk_body(self, body);
127 lint_callback!(self, check_body_post, body);
130 fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
131 let generics = self.context.generics.take();
132 self.context.generics = it.kind.generics();
133 let old_cached_typeck_results = self.context.cached_typeck_results.take();
134 let old_enclosing_body = self.context.enclosing_body.take();
135 self.with_lint_attrs(it.hir_id(), |cx| {
136 cx.with_param_env(it.hir_id(), |cx| {
137 lint_callback!(cx, check_item, it);
138 hir_visit::walk_item(cx, it);
139 lint_callback!(cx, check_item_post, it);
142 self.context.enclosing_body = old_enclosing_body;
143 self.context.cached_typeck_results.set(old_cached_typeck_results);
144 self.context.generics = generics;
147 fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
148 self.with_lint_attrs(it.hir_id(), |cx| {
149 cx.with_param_env(it.hir_id(), |cx| {
150 lint_callback!(cx, check_foreign_item, it);
151 hir_visit::walk_foreign_item(cx, it);
156 fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
157 lint_callback!(self, check_pat, p);
158 hir_visit::walk_pat(self, p);
161 fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
162 self.with_lint_attrs(e.hir_id, |cx| {
163 lint_callback!(cx, check_expr, e);
164 hir_visit::walk_expr(cx, e);
165 lint_callback!(cx, check_expr_post, e);
169 fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
170 // See `EarlyContextAndPass::visit_stmt` for an explanation
171 // of why we call `walk_stmt` outside of `with_lint_attrs`
172 self.with_lint_attrs(s.hir_id, |cx| {
173 lint_callback!(cx, check_stmt, s);
175 hir_visit::walk_stmt(self, s);
180 fk: hir_visit::FnKind<'tcx>,
181 decl: &'tcx hir::FnDecl<'tcx>,
182 body_id: hir::BodyId,
186 // Wrap in typeck results here, not just in visit_nested_body,
187 // in order for `check_fn` to be able to use them.
188 let old_enclosing_body = self.context.enclosing_body.replace(body_id);
189 let old_cached_typeck_results = self.context.cached_typeck_results.take();
190 let body = self.context.tcx.hir().body(body_id);
191 lint_callback!(self, check_fn, fk, decl, body, span, id);
192 hir_visit::walk_fn(self, fk, decl, body_id, span, id);
193 self.context.enclosing_body = old_enclosing_body;
194 self.context.cached_typeck_results.set(old_cached_typeck_results);
197 fn visit_variant_data(
199 s: &'tcx hir::VariantData<'tcx>,
201 _: &'tcx hir::Generics<'tcx>,
205 lint_callback!(self, check_struct_def, s);
206 hir_visit::walk_struct_def(self, s);
209 fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
210 self.with_lint_attrs(s.hir_id, |cx| {
211 lint_callback!(cx, check_field_def, s);
212 hir_visit::walk_field_def(cx, s);
218 v: &'tcx hir::Variant<'tcx>,
219 g: &'tcx hir::Generics<'tcx>,
222 self.with_lint_attrs(v.id, |cx| {
223 lint_callback!(cx, check_variant, v);
224 hir_visit::walk_variant(cx, v, g, item_id);
228 fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
229 lint_callback!(self, check_ty, t);
230 hir_visit::walk_ty(self, t);
233 fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
234 hir_visit::walk_inf(self, inf);
237 fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
238 if !self.context.only_module {
239 self.process_mod(m, s, n);
243 fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
244 self.with_lint_attrs(l.hir_id, |cx| {
245 lint_callback!(cx, check_local, l);
246 hir_visit::walk_local(cx, l);
250 fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
251 lint_callback!(self, check_block, b);
252 hir_visit::walk_block(self, b);
253 lint_callback!(self, check_block_post, b);
256 fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
257 lint_callback!(self, check_arm, a);
258 hir_visit::walk_arm(self, a);
261 fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
262 lint_callback!(self, check_generic_param, p);
263 hir_visit::walk_generic_param(self, p);
266 fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
267 lint_callback!(self, check_generics, g);
268 hir_visit::walk_generics(self, g);
271 fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
272 hir_visit::walk_where_predicate(self, p);
275 fn visit_poly_trait_ref(
277 t: &'tcx hir::PolyTraitRef<'tcx>,
278 m: hir::TraitBoundModifier,
280 lint_callback!(self, check_poly_trait_ref, t, m);
281 hir_visit::walk_poly_trait_ref(self, t, m);
284 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
285 let generics = self.context.generics.take();
286 self.context.generics = Some(&trait_item.generics);
287 self.with_lint_attrs(trait_item.hir_id(), |cx| {
288 cx.with_param_env(trait_item.hir_id(), |cx| {
289 lint_callback!(cx, check_trait_item, trait_item);
290 hir_visit::walk_trait_item(cx, trait_item);
293 self.context.generics = generics;
296 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
297 let generics = self.context.generics.take();
298 self.context.generics = Some(&impl_item.generics);
299 self.with_lint_attrs(impl_item.hir_id(), |cx| {
300 cx.with_param_env(impl_item.hir_id(), |cx| {
301 lint_callback!(cx, check_impl_item, impl_item);
302 hir_visit::walk_impl_item(cx, impl_item);
303 lint_callback!(cx, check_impl_item_post, impl_item);
306 self.context.generics = generics;
309 fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
310 hir_visit::walk_lifetime(self, lt);
313 fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
314 lint_callback!(self, check_path, p, id);
315 hir_visit::walk_path(self, p);
318 fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
319 lint_callback!(self, check_attribute, attr);
323 struct LateLintPassObjects<'a> {
324 lints: &'a mut [LateLintPassObject],
327 #[allow(rustc::lint_pass_impl_without_macro)]
328 impl LintPass for LateLintPassObjects<'_> {
329 fn name(&self) -> &'static str {
334 macro_rules! expand_late_lint_pass_impl_methods {
335 ([$hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
336 $(fn $name(&mut self, context: &LateContext<$hir>, $($param: $arg),*) {
337 for obj in self.lints.iter_mut() {
338 obj.$name(context, $($param),*);
344 macro_rules! late_lint_pass_impl {
345 ([], [$hir:tt], $methods:tt) => {
346 impl<$hir> LateLintPass<$hir> for LateLintPassObjects<'_> {
347 expand_late_lint_pass_impl_methods!([$hir], $methods);
352 crate::late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
354 fn late_lint_mod_pass<'tcx, T: LateLintPass<'tcx>>(
356 module_def_id: LocalDefId,
359 let access_levels = &tcx.privacy_access_levels(());
361 let context = LateContext {
363 enclosing_body: None,
364 cached_typeck_results: Cell::new(None),
365 param_env: ty::ParamEnv::empty(),
367 lint_store: unerased_lint_store(tcx),
368 last_node_with_lint_attrs: tcx.hir().local_def_id_to_hir_id(module_def_id),
373 let mut cx = LateContextAndPass { context, pass };
375 let (module, span, hir_id) = tcx.hir().get_module(module_def_id);
376 cx.process_mod(module, span, hir_id);
378 // Visit the crate attributes
379 if hir_id == hir::CRATE_HIR_ID {
380 for attr in tcx.hir().attrs(hir::CRATE_HIR_ID).iter() {
381 cx.visit_attribute(attr)
386 pub fn late_lint_mod<'tcx, T: LateLintPass<'tcx>>(
388 module_def_id: LocalDefId,
391 if tcx.sess.opts.unstable_opts.no_interleave_lints {
392 // These passes runs in late_lint_crate with -Z no_interleave_lints
396 late_lint_mod_pass(tcx, module_def_id, builtin_lints);
398 let mut passes: Vec<_> =
399 unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
401 if !passes.is_empty() {
402 late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
406 fn late_lint_pass_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
407 let access_levels = &tcx.privacy_access_levels(());
409 let context = LateContext {
411 enclosing_body: None,
412 cached_typeck_results: Cell::new(None),
413 param_env: ty::ParamEnv::empty(),
415 lint_store: unerased_lint_store(tcx),
416 last_node_with_lint_attrs: hir::CRATE_HIR_ID,
421 let mut cx = LateContextAndPass { context, pass };
423 // Visit the whole crate.
424 cx.with_lint_attrs(hir::CRATE_HIR_ID, |cx| {
425 // since the root module isn't visited as an item (because it isn't an
426 // item), warn for it here.
427 lint_callback!(cx, check_crate,);
428 tcx.hir().walk_toplevel_module(cx);
429 tcx.hir().walk_attributes(cx);
430 lint_callback!(cx, check_crate_post,);
434 fn late_lint_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
435 let mut passes = unerased_lint_store(tcx).late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
437 if !tcx.sess.opts.unstable_opts.no_interleave_lints {
438 if !passes.is_empty() {
439 late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
442 late_lint_pass_crate(tcx, builtin_lints);
444 for pass in &mut passes {
445 tcx.sess.prof.extra_verbose_generic_activity("run_late_lint", pass.name()).run(|| {
446 late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
450 let mut passes: Vec<_> =
451 unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
453 for pass in &mut passes {
454 tcx.sess.prof.extra_verbose_generic_activity("run_late_module_lint", pass.name()).run(
456 late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
463 /// Performs lint checking on a crate.
464 pub fn check_crate<'tcx, T: LateLintPass<'tcx>>(
466 builtin_lints: impl FnOnce() -> T + Send,
470 tcx.sess.time("crate_lints", || {
471 // Run whole crate non-incremental lints
472 late_lint_crate(tcx, builtin_lints());
476 tcx.sess.time("module_lints", || {
477 // Run per-module lints
478 tcx.hir().par_for_each_module(|module| tcx.ensure().lint_mod(module));