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;
33 /// Extract the `LintStore` from the query context.
34 /// This function exists because we've erased `LintStore` as `dyn Any` in the context.
35 pub fn unerased_lint_store(tcx: TyCtxt<'_>) -> &LintStore {
36 let store: &dyn Any = &*tcx.lint_store;
37 store.downcast_ref().unwrap()
40 macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
41 $cx.pass.$f(&$cx.context, $($args),*);
44 struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
45 context: LateContext<'tcx>,
49 impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'tcx, T> {
50 /// Merge the lints specified by any lint attributes into the
51 /// current lint context, call the provided function, then reset the
52 /// lints in effect to their previous state.
53 fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
57 let attrs = self.context.tcx.hir().attrs(id);
58 let prev = self.context.last_node_with_lint_attrs;
59 self.context.last_node_with_lint_attrs = id;
60 debug!("late context: enter_attrs({:?})", attrs);
61 lint_callback!(self, enter_lint_attrs, attrs);
63 debug!("late context: exit_attrs({:?})", attrs);
64 lint_callback!(self, exit_lint_attrs, attrs);
65 self.context.last_node_with_lint_attrs = prev;
68 fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
72 let old_param_env = self.context.param_env;
73 self.context.param_env =
74 self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
76 self.context.param_env = old_param_env;
79 fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, n: hir::HirId) {
80 lint_callback!(self, check_mod, m, n);
81 hir_visit::walk_mod(self, m, n);
85 impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPass<'tcx, T> {
86 type NestedFilter = nested_filter::All;
88 /// Because lints are scoped lexically, we want to walk nested
89 /// items in the context of the outer item, so enable
91 fn nested_visit_map(&mut self) -> Self::Map {
92 self.context.tcx.hir()
95 fn visit_nested_body(&mut self, body_id: hir::BodyId) {
96 let old_enclosing_body = self.context.enclosing_body.replace(body_id);
97 let old_cached_typeck_results = self.context.cached_typeck_results.get();
99 // HACK(eddyb) avoid trashing `cached_typeck_results` when we're
100 // nested in `visit_fn`, which may have already resulted in them
102 if old_enclosing_body != Some(body_id) {
103 self.context.cached_typeck_results.set(None);
106 let body = self.context.tcx.hir().body(body_id);
107 self.visit_body(body);
108 self.context.enclosing_body = old_enclosing_body;
110 // See HACK comment above.
111 if old_enclosing_body != Some(body_id) {
112 self.context.cached_typeck_results.set(old_cached_typeck_results);
116 fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
117 self.with_lint_attrs(param.hir_id, |cx| {
118 hir_visit::walk_param(cx, param);
122 fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
123 lint_callback!(self, check_body, body);
124 hir_visit::walk_body(self, body);
125 lint_callback!(self, check_body_post, body);
128 fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
129 let generics = self.context.generics.take();
130 self.context.generics = it.kind.generics();
131 let old_cached_typeck_results = self.context.cached_typeck_results.take();
132 let old_enclosing_body = self.context.enclosing_body.take();
133 self.with_lint_attrs(it.hir_id(), |cx| {
134 cx.with_param_env(it.hir_id(), |cx| {
135 lint_callback!(cx, check_item, it);
136 hir_visit::walk_item(cx, it);
137 lint_callback!(cx, check_item_post, it);
140 self.context.enclosing_body = old_enclosing_body;
141 self.context.cached_typeck_results.set(old_cached_typeck_results);
142 self.context.generics = generics;
145 fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
146 self.with_lint_attrs(it.hir_id(), |cx| {
147 cx.with_param_env(it.hir_id(), |cx| {
148 lint_callback!(cx, check_foreign_item, it);
149 hir_visit::walk_foreign_item(cx, it);
154 fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
155 lint_callback!(self, check_pat, p);
156 hir_visit::walk_pat(self, p);
159 fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
160 self.with_lint_attrs(e.hir_id, |cx| {
161 lint_callback!(cx, check_expr, e);
162 hir_visit::walk_expr(cx, e);
163 lint_callback!(cx, check_expr_post, e);
167 fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
168 // See `EarlyContextAndPass::visit_stmt` for an explanation
169 // of why we call `walk_stmt` outside of `with_lint_attrs`
170 self.with_lint_attrs(s.hir_id, |cx| {
171 lint_callback!(cx, check_stmt, s);
173 hir_visit::walk_stmt(self, s);
178 fk: hir_visit::FnKind<'tcx>,
179 decl: &'tcx hir::FnDecl<'tcx>,
180 body_id: hir::BodyId,
184 // Wrap in typeck results here, not just in visit_nested_body,
185 // in order for `check_fn` to be able to use them.
186 let old_enclosing_body = self.context.enclosing_body.replace(body_id);
187 let old_cached_typeck_results = self.context.cached_typeck_results.take();
188 let body = self.context.tcx.hir().body(body_id);
189 lint_callback!(self, check_fn, fk, decl, body, span, id);
190 hir_visit::walk_fn(self, fk, decl, body_id, id);
191 self.context.enclosing_body = old_enclosing_body;
192 self.context.cached_typeck_results.set(old_cached_typeck_results);
195 fn visit_variant_data(&mut self, s: &'tcx hir::VariantData<'tcx>) {
196 lint_callback!(self, check_struct_def, s);
197 hir_visit::walk_struct_def(self, s);
200 fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
201 self.with_lint_attrs(s.hir_id, |cx| {
202 lint_callback!(cx, check_field_def, s);
203 hir_visit::walk_field_def(cx, s);
207 fn visit_variant(&mut self, v: &'tcx hir::Variant<'tcx>) {
208 self.with_lint_attrs(v.hir_id, |cx| {
209 lint_callback!(cx, check_variant, v);
210 hir_visit::walk_variant(cx, v);
214 fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
215 lint_callback!(self, check_ty, t);
216 hir_visit::walk_ty(self, t);
219 fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
220 hir_visit::walk_inf(self, inf);
223 fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, _: Span, n: hir::HirId) {
224 if !self.context.only_module {
225 self.process_mod(m, n);
229 fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
230 self.with_lint_attrs(l.hir_id, |cx| {
231 lint_callback!(cx, check_local, l);
232 hir_visit::walk_local(cx, l);
236 fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
237 lint_callback!(self, check_block, b);
238 hir_visit::walk_block(self, b);
239 lint_callback!(self, check_block_post, b);
242 fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
243 lint_callback!(self, check_arm, a);
244 hir_visit::walk_arm(self, a);
247 fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
248 lint_callback!(self, check_generic_param, p);
249 hir_visit::walk_generic_param(self, p);
252 fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
253 lint_callback!(self, check_generics, g);
254 hir_visit::walk_generics(self, g);
257 fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
258 hir_visit::walk_where_predicate(self, p);
261 fn visit_poly_trait_ref(&mut self, t: &'tcx hir::PolyTraitRef<'tcx>) {
262 lint_callback!(self, check_poly_trait_ref, t);
263 hir_visit::walk_poly_trait_ref(self, t);
266 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
267 let generics = self.context.generics.take();
268 self.context.generics = Some(&trait_item.generics);
269 self.with_lint_attrs(trait_item.hir_id(), |cx| {
270 cx.with_param_env(trait_item.hir_id(), |cx| {
271 lint_callback!(cx, check_trait_item, trait_item);
272 hir_visit::walk_trait_item(cx, trait_item);
275 self.context.generics = generics;
278 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
279 let generics = self.context.generics.take();
280 self.context.generics = Some(&impl_item.generics);
281 self.with_lint_attrs(impl_item.hir_id(), |cx| {
282 cx.with_param_env(impl_item.hir_id(), |cx| {
283 lint_callback!(cx, check_impl_item, impl_item);
284 hir_visit::walk_impl_item(cx, impl_item);
285 lint_callback!(cx, check_impl_item_post, impl_item);
288 self.context.generics = generics;
291 fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
292 hir_visit::walk_lifetime(self, lt);
295 fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
296 lint_callback!(self, check_path, p, id);
297 hir_visit::walk_path(self, p);
300 fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
301 lint_callback!(self, check_attribute, attr);
305 struct LateLintPassObjects<'a, 'tcx> {
306 lints: &'a mut [LateLintPassObject<'tcx>],
309 #[allow(rustc::lint_pass_impl_without_macro)]
310 impl LintPass for LateLintPassObjects<'_, '_> {
311 fn name(&self) -> &'static str {
316 macro_rules! expand_late_lint_pass_impl_methods {
317 ([$hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
318 $(fn $name(&mut self, context: &LateContext<$hir>, $($param: $arg),*) {
319 for obj in self.lints.iter_mut() {
320 obj.$name(context, $($param),*);
326 macro_rules! late_lint_pass_impl {
327 ([], [$hir:tt], $methods:tt) => {
328 impl<$hir> LateLintPass<$hir> for LateLintPassObjects<'_, $hir> {
329 expand_late_lint_pass_impl_methods!([$hir], $methods);
334 crate::late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
336 fn late_lint_mod_pass<'tcx, T: LateLintPass<'tcx>>(
338 module_def_id: LocalDefId,
341 let effective_visibilities = &tcx.effective_visibilities(());
343 let context = LateContext {
345 enclosing_body: None,
346 cached_typeck_results: Cell::new(None),
347 param_env: ty::ParamEnv::empty(),
348 effective_visibilities,
349 lint_store: unerased_lint_store(tcx),
350 last_node_with_lint_attrs: tcx.hir().local_def_id_to_hir_id(module_def_id),
355 let mut cx = LateContextAndPass { context, pass };
357 let (module, _span, hir_id) = tcx.hir().get_module(module_def_id);
358 cx.process_mod(module, hir_id);
360 // Visit the crate attributes
361 if hir_id == hir::CRATE_HIR_ID {
362 for attr in tcx.hir().attrs(hir::CRATE_HIR_ID).iter() {
363 cx.visit_attribute(attr)
368 pub fn late_lint_mod<'tcx, T: LateLintPass<'tcx>>(
370 module_def_id: LocalDefId,
373 if tcx.sess.opts.unstable_opts.no_interleave_lints {
374 // These passes runs in late_lint_crate with -Z no_interleave_lints
378 late_lint_mod_pass(tcx, module_def_id, builtin_lints);
380 let mut passes: Vec<_> =
381 unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)(tcx)).collect();
383 if !passes.is_empty() {
384 late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
388 fn late_lint_pass_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
389 let effective_visibilities = &tcx.effective_visibilities(());
391 let context = LateContext {
393 enclosing_body: None,
394 cached_typeck_results: Cell::new(None),
395 param_env: ty::ParamEnv::empty(),
396 effective_visibilities,
397 lint_store: unerased_lint_store(tcx),
398 last_node_with_lint_attrs: hir::CRATE_HIR_ID,
403 let mut cx = LateContextAndPass { context, pass };
405 // Visit the whole crate.
406 cx.with_lint_attrs(hir::CRATE_HIR_ID, |cx| {
407 // since the root module isn't visited as an item (because it isn't an
408 // item), warn for it here.
409 lint_callback!(cx, check_crate,);
410 tcx.hir().walk_toplevel_module(cx);
411 tcx.hir().walk_attributes(cx);
412 lint_callback!(cx, check_crate_post,);
416 fn late_lint_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
418 unerased_lint_store(tcx).late_passes.iter().map(|p| (p)(tcx)).collect::<Vec<_>>();
420 if !tcx.sess.opts.unstable_opts.no_interleave_lints {
421 if !passes.is_empty() {
422 late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
425 late_lint_pass_crate(tcx, builtin_lints);
427 for pass in &mut passes {
428 tcx.sess.prof.verbose_generic_activity_with_arg("run_late_lint", pass.name()).run(
430 late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
435 let mut passes: Vec<_> =
436 unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)(tcx)).collect();
438 for pass in &mut passes {
441 .verbose_generic_activity_with_arg("run_late_module_lint", pass.name())
443 late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
449 /// Performs lint checking on a crate.
450 pub fn check_crate<'tcx, T: LateLintPass<'tcx>>(
452 builtin_lints: impl FnOnce() -> T + Send,
456 tcx.sess.time("crate_lints", || {
457 // Run whole crate non-incremental lints
458 late_lint_crate(tcx, builtin_lints());
462 tcx.sess.time("module_lints", || {
463 // Run per-module lints
464 tcx.hir().par_for_each_module(|module| tcx.ensure().lint_mod(module));