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;
32 /// Extract the `LintStore` from the query context.
33 /// This function exists because we've erased `LintStore` as `dyn Any` in the context.
34 pub fn unerased_lint_store(tcx: TyCtxt<'_>) -> &LintStore {
35 let store: &dyn Any = &*tcx.lint_store;
36 store.downcast_ref().unwrap()
39 macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
40 $cx.pass.$f(&$cx.context, $($args),*);
43 struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
44 context: LateContext<'tcx>,
48 impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'tcx, T> {
49 /// Merge the lints specified by any lint attributes into the
50 /// current lint context, call the provided function, then reset the
51 /// lints in effect to their previous state.
52 fn with_lint_attrs<F>(&mut self, id: hir::HirId, f: F)
56 let attrs = self.context.tcx.hir().attrs(id);
57 let prev = self.context.last_node_with_lint_attrs;
58 self.context.last_node_with_lint_attrs = id;
59 debug!("late context: enter_attrs({:?})", attrs);
60 lint_callback!(self, enter_lint_attrs, attrs);
62 debug!("late context: exit_attrs({:?})", attrs);
63 lint_callback!(self, exit_lint_attrs, attrs);
64 self.context.last_node_with_lint_attrs = prev;
67 fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
71 let old_param_env = self.context.param_env;
72 self.context.param_env =
73 self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
75 self.context.param_env = old_param_env;
78 fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, n: hir::HirId) {
79 lint_callback!(self, check_mod, m, n);
80 hir_visit::walk_mod(self, m, n);
84 impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPass<'tcx, T> {
85 type NestedFilter = nested_filter::All;
87 /// Because lints are scoped lexically, we want to walk nested
88 /// items in the context of the outer item, so enable
90 fn nested_visit_map(&mut self) -> Self::Map {
91 self.context.tcx.hir()
94 fn visit_nested_body(&mut self, body_id: hir::BodyId) {
95 let old_enclosing_body = self.context.enclosing_body.replace(body_id);
96 let old_cached_typeck_results = self.context.cached_typeck_results.get();
98 // HACK(eddyb) avoid trashing `cached_typeck_results` when we're
99 // nested in `visit_fn`, which may have already resulted in them
101 if old_enclosing_body != Some(body_id) {
102 self.context.cached_typeck_results.set(None);
105 let body = self.context.tcx.hir().body(body_id);
106 self.visit_body(body);
107 self.context.enclosing_body = old_enclosing_body;
109 // See HACK comment above.
110 if old_enclosing_body != Some(body_id) {
111 self.context.cached_typeck_results.set(old_cached_typeck_results);
115 fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
116 self.with_lint_attrs(param.hir_id, |cx| {
117 hir_visit::walk_param(cx, param);
121 fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
122 lint_callback!(self, check_body, body);
123 hir_visit::walk_body(self, body);
124 lint_callback!(self, check_body_post, body);
127 fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
128 let generics = self.context.generics.take();
129 self.context.generics = it.kind.generics();
130 let old_cached_typeck_results = self.context.cached_typeck_results.take();
131 let old_enclosing_body = self.context.enclosing_body.take();
132 self.with_lint_attrs(it.hir_id(), |cx| {
133 cx.with_param_env(it.hir_id(), |cx| {
134 lint_callback!(cx, check_item, it);
135 hir_visit::walk_item(cx, it);
136 lint_callback!(cx, check_item_post, it);
139 self.context.enclosing_body = old_enclosing_body;
140 self.context.cached_typeck_results.set(old_cached_typeck_results);
141 self.context.generics = generics;
144 fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
145 self.with_lint_attrs(it.hir_id(), |cx| {
146 cx.with_param_env(it.hir_id(), |cx| {
147 lint_callback!(cx, check_foreign_item, it);
148 hir_visit::walk_foreign_item(cx, it);
153 fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
154 lint_callback!(self, check_pat, p);
155 hir_visit::walk_pat(self, p);
158 fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
159 self.with_lint_attrs(e.hir_id, |cx| {
160 lint_callback!(cx, check_expr, e);
161 hir_visit::walk_expr(cx, e);
162 lint_callback!(cx, check_expr_post, e);
166 fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
167 // See `EarlyContextAndPass::visit_stmt` for an explanation
168 // of why we call `walk_stmt` outside of `with_lint_attrs`
169 self.with_lint_attrs(s.hir_id, |cx| {
170 lint_callback!(cx, check_stmt, s);
172 hir_visit::walk_stmt(self, s);
177 fk: hir_visit::FnKind<'tcx>,
178 decl: &'tcx hir::FnDecl<'tcx>,
179 body_id: hir::BodyId,
183 // Wrap in typeck results here, not just in visit_nested_body,
184 // in order for `check_fn` to be able to use them.
185 let old_enclosing_body = self.context.enclosing_body.replace(body_id);
186 let old_cached_typeck_results = self.context.cached_typeck_results.take();
187 let body = self.context.tcx.hir().body(body_id);
188 lint_callback!(self, check_fn, fk, decl, body, span, id);
189 hir_visit::walk_fn(self, fk, decl, body_id, id);
190 self.context.enclosing_body = old_enclosing_body;
191 self.context.cached_typeck_results.set(old_cached_typeck_results);
194 fn visit_variant_data(&mut self, s: &'tcx hir::VariantData<'tcx>) {
195 lint_callback!(self, check_struct_def, s);
196 hir_visit::walk_struct_def(self, s);
199 fn visit_field_def(&mut self, s: &'tcx hir::FieldDef<'tcx>) {
200 self.with_lint_attrs(s.hir_id, |cx| {
201 lint_callback!(cx, check_field_def, s);
202 hir_visit::walk_field_def(cx, s);
206 fn visit_variant(&mut self, v: &'tcx hir::Variant<'tcx>) {
207 self.with_lint_attrs(v.hir_id, |cx| {
208 lint_callback!(cx, check_variant, v);
209 hir_visit::walk_variant(cx, v);
213 fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
214 lint_callback!(self, check_ty, t);
215 hir_visit::walk_ty(self, t);
218 fn visit_infer(&mut self, inf: &'tcx hir::InferArg) {
219 hir_visit::walk_inf(self, inf);
222 fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, _: Span, n: hir::HirId) {
223 if !self.context.only_module {
224 self.process_mod(m, n);
228 fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
229 self.with_lint_attrs(l.hir_id, |cx| {
230 lint_callback!(cx, check_local, l);
231 hir_visit::walk_local(cx, l);
235 fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
236 lint_callback!(self, check_block, b);
237 hir_visit::walk_block(self, b);
238 lint_callback!(self, check_block_post, b);
241 fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
242 lint_callback!(self, check_arm, a);
243 hir_visit::walk_arm(self, a);
246 fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
247 lint_callback!(self, check_generic_param, p);
248 hir_visit::walk_generic_param(self, p);
251 fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
252 lint_callback!(self, check_generics, g);
253 hir_visit::walk_generics(self, g);
256 fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
257 hir_visit::walk_where_predicate(self, p);
260 fn visit_poly_trait_ref(&mut self, t: &'tcx hir::PolyTraitRef<'tcx>) {
261 lint_callback!(self, check_poly_trait_ref, t);
262 hir_visit::walk_poly_trait_ref(self, t);
265 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
266 let generics = self.context.generics.take();
267 self.context.generics = Some(&trait_item.generics);
268 self.with_lint_attrs(trait_item.hir_id(), |cx| {
269 cx.with_param_env(trait_item.hir_id(), |cx| {
270 lint_callback!(cx, check_trait_item, trait_item);
271 hir_visit::walk_trait_item(cx, trait_item);
274 self.context.generics = generics;
277 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
278 let generics = self.context.generics.take();
279 self.context.generics = Some(&impl_item.generics);
280 self.with_lint_attrs(impl_item.hir_id(), |cx| {
281 cx.with_param_env(impl_item.hir_id(), |cx| {
282 lint_callback!(cx, check_impl_item, impl_item);
283 hir_visit::walk_impl_item(cx, impl_item);
284 lint_callback!(cx, check_impl_item_post, impl_item);
287 self.context.generics = generics;
290 fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
291 hir_visit::walk_lifetime(self, lt);
294 fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
295 lint_callback!(self, check_path, p, id);
296 hir_visit::walk_path(self, p);
299 fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
300 lint_callback!(self, check_attribute, attr);
304 struct LateLintPassObjects<'a, 'tcx> {
305 lints: &'a mut [LateLintPassObject<'tcx>],
308 #[allow(rustc::lint_pass_impl_without_macro)]
309 impl LintPass for LateLintPassObjects<'_, '_> {
310 fn name(&self) -> &'static str {
315 macro_rules! late_lint_pass_impl {
316 ([], [$hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => {
317 impl<$hir> LateLintPass<$hir> for LateLintPassObjects<'_, $hir> {
318 $(fn $name(&mut self, context: &LateContext<$hir>, $($param: $arg),*) {
319 for obj in self.lints.iter_mut() {
320 obj.$name(context, $($param),*);
327 crate::late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
329 pub fn late_lint_mod<'tcx, T: LateLintPass<'tcx> + 'tcx>(
331 module_def_id: LocalDefId,
334 let context = LateContext {
336 enclosing_body: None,
337 cached_typeck_results: Cell::new(None),
338 param_env: ty::ParamEnv::empty(),
339 effective_visibilities: &tcx.effective_visibilities(()),
340 lint_store: unerased_lint_store(tcx),
341 last_node_with_lint_attrs: tcx.hir().local_def_id_to_hir_id(module_def_id),
346 let mut passes: Vec<_> =
347 unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)(tcx)).collect();
348 passes.push(Box::new(builtin_lints));
349 let pass = LateLintPassObjects { lints: &mut passes[..] };
351 let mut cx = LateContextAndPass { context, pass };
353 let (module, _span, hir_id) = tcx.hir().get_module(module_def_id);
354 cx.process_mod(module, hir_id);
356 // Visit the crate attributes
357 if hir_id == hir::CRATE_HIR_ID {
358 for attr in tcx.hir().attrs(hir::CRATE_HIR_ID).iter() {
359 cx.visit_attribute(attr)
364 fn late_lint_pass_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
365 let effective_visibilities = &tcx.effective_visibilities(());
367 let context = LateContext {
369 enclosing_body: None,
370 cached_typeck_results: Cell::new(None),
371 param_env: ty::ParamEnv::empty(),
372 effective_visibilities,
373 lint_store: unerased_lint_store(tcx),
374 last_node_with_lint_attrs: hir::CRATE_HIR_ID,
379 let mut cx = LateContextAndPass { context, pass };
381 // Visit the whole crate.
382 cx.with_lint_attrs(hir::CRATE_HIR_ID, |cx| {
383 // since the root module isn't visited as an item (because it isn't an
384 // item), warn for it here.
385 lint_callback!(cx, check_crate,);
386 tcx.hir().walk_toplevel_module(cx);
387 tcx.hir().walk_attributes(cx);
388 lint_callback!(cx, check_crate_post,);
392 fn late_lint_crate<'tcx, T: LateLintPass<'tcx> + 'tcx>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
394 unerased_lint_store(tcx).late_passes.iter().map(|p| (p)(tcx)).collect::<Vec<_>>();
395 passes.push(Box::new(builtin_lints));
397 late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
400 /// Performs lint checking on a crate.
401 pub fn check_crate<'tcx, T: LateLintPass<'tcx> + 'tcx>(
403 builtin_lints: impl FnOnce() -> T + Send,
407 tcx.sess.time("crate_lints", || {
408 // Run whole crate non-incremental lints
409 late_lint_crate(tcx, builtin_lints());
413 tcx.sess.time("module_lints", || {
414 // Run per-module lints
415 tcx.hir().par_for_each_module(|module| tcx.ensure().lint_mod(module));