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::context::{EarlyContext, LintContext, LintStore};
18 use crate::passes::{EarlyLintPass, EarlyLintPassObject};
19 use rustc_ast::ptr::P;
20 use rustc_ast::visit::{self as ast_visit, Visitor};
21 use rustc_ast::{self as ast, walk_list, HasAttrs};
22 use rustc_middle::ty::RegisteredTools;
23 use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
24 use rustc_session::Session;
25 use rustc_span::symbol::Ident;
28 macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
29 $cx.pass.$f(&$cx.context, $($args),*);
32 /// Implements the AST traversal for early lint passes. `T` provides the
33 /// `check_*` methods.
34 pub struct EarlyContextAndPass<'a, T: EarlyLintPass> {
35 context: EarlyContext<'a>,
39 impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
40 // This always-inlined function is for the hot call site.
42 fn inlined_check_id(&mut self, id: ast::NodeId) {
43 for early_lint in self.context.buffered.take(id) {
44 let BufferedEarlyLint { span, msg, node_id: _, lint_id, diagnostic } = early_lint;
45 self.context.lookup_with_diagnostics(
55 // This non-inlined function is for the cold call sites.
56 fn check_id(&mut self, id: ast::NodeId) {
57 self.inlined_check_id(id)
60 /// Merge the lints specified by any lint attributes into the
61 /// current lint context, call the provided function, then reset the
62 /// lints in effect to their previous state.
63 fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'a [ast::Attribute], f: F)
67 let is_crate_node = id == ast::CRATE_NODE_ID;
69 let push = self.context.builder.push(attrs, is_crate_node, None);
71 self.inlined_check_id(id);
72 debug!("early context: enter_attrs({:?})", attrs);
73 lint_callback!(self, enter_lint_attrs, attrs);
75 debug!("early context: exit_attrs({:?})", attrs);
76 lint_callback!(self, exit_lint_attrs, attrs);
77 self.context.builder.pop(push);
81 impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T> {
82 fn visit_param(&mut self, param: &'a ast::Param) {
83 self.with_lint_attrs(param.id, ¶m.attrs, |cx| {
84 lint_callback!(cx, check_param, param);
85 ast_visit::walk_param(cx, param);
89 fn visit_item(&mut self, it: &'a ast::Item) {
90 self.with_lint_attrs(it.id, &it.attrs, |cx| {
91 lint_callback!(cx, check_item, it);
92 ast_visit::walk_item(cx, it);
93 lint_callback!(cx, check_item_post, it);
97 fn visit_foreign_item(&mut self, it: &'a ast::ForeignItem) {
98 self.with_lint_attrs(it.id, &it.attrs, |cx| {
99 ast_visit::walk_foreign_item(cx, it);
103 fn visit_pat(&mut self, p: &'a ast::Pat) {
104 lint_callback!(self, check_pat, p);
106 ast_visit::walk_pat(self, p);
107 lint_callback!(self, check_pat_post, p);
110 fn visit_pat_field(&mut self, field: &'a ast::PatField) {
111 self.with_lint_attrs(field.id, &field.attrs, |cx| {
112 ast_visit::walk_pat_field(cx, field);
116 fn visit_anon_const(&mut self, c: &'a ast::AnonConst) {
118 ast_visit::walk_anon_const(self, c);
121 fn visit_expr(&mut self, e: &'a ast::Expr) {
122 self.with_lint_attrs(e.id, &e.attrs, |cx| {
123 lint_callback!(cx, check_expr, e);
124 ast_visit::walk_expr(cx, e);
128 fn visit_expr_field(&mut self, f: &'a ast::ExprField) {
129 self.with_lint_attrs(f.id, &f.attrs, |cx| {
130 ast_visit::walk_expr_field(cx, f);
134 fn visit_stmt(&mut self, s: &'a ast::Stmt) {
135 // Add the statement's lint attributes to our
136 // current state when checking the statement itself.
137 // This allows us to handle attributes like
138 // `#[allow(unused_doc_comments)]`, which apply to
139 // sibling attributes on the same target
141 // Note that statements get their attributes from
142 // the AST struct that they wrap (e.g. an item)
143 self.with_lint_attrs(s.id, s.attrs(), |cx| {
144 lint_callback!(cx, check_stmt, s);
147 // The visitor for the AST struct wrapped
148 // by the statement (e.g. `Item`) will call
149 // `with_lint_attrs`, so do this walk
150 // outside of the above `with_lint_attrs` call
151 ast_visit::walk_stmt(self, s);
154 fn visit_fn(&mut self, fk: ast_visit::FnKind<'a>, span: Span, id: ast::NodeId) {
155 lint_callback!(self, check_fn, fk, span, id);
157 ast_visit::walk_fn(self, fk);
159 // Explicitly check for lints associated with 'closure_id', since
160 // it does not have a corresponding AST node
161 if let ast_visit::FnKind::Fn(_, _, sig, _, _, _) = fk {
162 if let ast::Async::Yes { closure_id, .. } = sig.header.asyncness {
163 self.check_id(closure_id);
168 fn visit_variant_data(&mut self, s: &'a ast::VariantData) {
169 if let Some(ctor_node_id) = s.ctor_node_id() {
170 self.check_id(ctor_node_id);
172 ast_visit::walk_struct_def(self, s);
175 fn visit_field_def(&mut self, s: &'a ast::FieldDef) {
176 self.with_lint_attrs(s.id, &s.attrs, |cx| {
177 ast_visit::walk_field_def(cx, s);
181 fn visit_variant(&mut self, v: &'a ast::Variant) {
182 self.with_lint_attrs(v.id, &v.attrs, |cx| {
183 lint_callback!(cx, check_variant, v);
184 ast_visit::walk_variant(cx, v);
188 fn visit_ty(&mut self, t: &'a ast::Ty) {
189 lint_callback!(self, check_ty, t);
191 ast_visit::walk_ty(self, t);
194 fn visit_ident(&mut self, ident: Ident) {
195 lint_callback!(self, check_ident, ident);
198 fn visit_local(&mut self, l: &'a ast::Local) {
199 self.with_lint_attrs(l.id, &l.attrs, |cx| {
200 lint_callback!(cx, check_local, l);
201 ast_visit::walk_local(cx, l);
205 fn visit_block(&mut self, b: &'a ast::Block) {
206 lint_callback!(self, check_block, b);
208 ast_visit::walk_block(self, b);
211 fn visit_arm(&mut self, a: &'a ast::Arm) {
212 self.with_lint_attrs(a.id, &a.attrs, |cx| {
213 lint_callback!(cx, check_arm, a);
214 ast_visit::walk_arm(cx, a);
218 fn visit_expr_post(&mut self, e: &'a ast::Expr) {
219 // Explicitly check for lints associated with 'closure_id', since
220 // it does not have a corresponding AST node
222 ast::ExprKind::Closure(box ast::Closure {
223 asyncness: ast::Async::Yes { closure_id, .. },
226 | ast::ExprKind::Async(_, closure_id, ..) => self.check_id(closure_id),
231 fn visit_generic_arg(&mut self, arg: &'a ast::GenericArg) {
232 lint_callback!(self, check_generic_arg, arg);
233 ast_visit::walk_generic_arg(self, arg);
236 fn visit_generic_param(&mut self, param: &'a ast::GenericParam) {
237 self.with_lint_attrs(param.id, ¶m.attrs, |cx| {
238 lint_callback!(cx, check_generic_param, param);
239 ast_visit::walk_generic_param(cx, param);
243 fn visit_generics(&mut self, g: &'a ast::Generics) {
244 lint_callback!(self, check_generics, g);
245 ast_visit::walk_generics(self, g);
248 fn visit_where_predicate(&mut self, p: &'a ast::WherePredicate) {
249 ast_visit::walk_where_predicate(self, p);
252 fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef) {
253 lint_callback!(self, check_poly_trait_ref, t);
254 ast_visit::walk_poly_trait_ref(self, t);
257 fn visit_assoc_item(&mut self, item: &'a ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
258 self.with_lint_attrs(item.id, &item.attrs, |cx| match ctxt {
259 ast_visit::AssocCtxt::Trait => {
260 lint_callback!(cx, check_trait_item, item);
261 ast_visit::walk_assoc_item(cx, item, ctxt);
263 ast_visit::AssocCtxt::Impl => {
264 lint_callback!(cx, check_impl_item, item);
265 ast_visit::walk_assoc_item(cx, item, ctxt);
270 fn visit_lifetime(&mut self, lt: &'a ast::Lifetime, _: ast_visit::LifetimeCtxt) {
271 self.check_id(lt.id);
274 fn visit_path(&mut self, p: &'a ast::Path, id: ast::NodeId) {
276 ast_visit::walk_path(self, p);
279 fn visit_path_segment(&mut self, s: &'a ast::PathSegment) {
281 ast_visit::walk_path_segment(self, s);
284 fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
285 lint_callback!(self, check_attribute, attr);
288 fn visit_mac_def(&mut self, mac: &'a ast::MacroDef, id: ast::NodeId) {
289 lint_callback!(self, check_mac_def, mac);
293 fn visit_mac_call(&mut self, mac: &'a ast::MacCall) {
294 lint_callback!(self, check_mac, mac);
295 ast_visit::walk_mac(self, mac);
299 // Combines multiple lint passes into a single pass, at runtime. Each
300 // `check_foo` method in `$methods` within this pass simply calls `check_foo`
301 // once per `$pass`. Compare with `declare_combined_early_lint_pass`, which is
302 // similar, but combines lint passes at compile time.
303 struct RuntimeCombinedEarlyLintPass<'a> {
304 passes: &'a mut [EarlyLintPassObject],
307 #[allow(rustc::lint_pass_impl_without_macro)]
308 impl LintPass for RuntimeCombinedEarlyLintPass<'_> {
309 fn name(&self) -> &'static str {
314 macro_rules! impl_early_lint_pass {
315 ([], [$($(#[$attr:meta])* fn $f:ident($($param:ident: $arg:ty),*);)*]) => (
316 impl EarlyLintPass for RuntimeCombinedEarlyLintPass<'_> {
317 $(fn $f(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
318 for pass in self.passes.iter_mut() {
319 pass.$f(context, $($param),*);
326 crate::early_lint_methods!(impl_early_lint_pass, []);
328 /// Early lints work on different nodes - either on the crate root, or on freshly loaded modules.
329 /// This trait generalizes over those nodes.
330 pub trait EarlyCheckNode<'a>: Copy {
331 fn id(self) -> ast::NodeId;
332 fn attrs<'b>(self) -> &'b [ast::Attribute]
335 fn check<'b, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'b, T>)
340 impl<'a> EarlyCheckNode<'a> for &'a ast::Crate {
341 fn id(self) -> ast::NodeId {
344 fn attrs<'b>(self) -> &'b [ast::Attribute]
350 fn check<'b, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'b, T>)
354 lint_callback!(cx, check_crate, self);
355 ast_visit::walk_crate(cx, self);
356 lint_callback!(cx, check_crate_post, self);
360 impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
361 fn id(self) -> ast::NodeId {
364 fn attrs<'b>(self) -> &'b [ast::Attribute]
370 fn check<'b, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'b, T>)
374 walk_list!(cx, visit_attribute, self.1);
375 walk_list!(cx, visit_item, self.2);
379 pub fn check_ast_node<'a>(
382 lint_store: &LintStore,
383 registered_tools: &RegisteredTools,
384 lint_buffer: Option<LintBuffer>,
385 builtin_lints: impl EarlyLintPass + 'static,
386 check_node: impl EarlyCheckNode<'a>,
388 let context = EarlyContext::new(
393 lint_buffer.unwrap_or_default(),
396 // Note: `passes` is often empty. In that case, it's faster to run
397 // `builtin_lints` directly rather than bundling it up into the
398 // `RuntimeCombinedEarlyLintPass`.
400 if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
401 if passes.is_empty() {
402 check_ast_node_inner(sess, check_node, context, builtin_lints);
404 let mut passes: Vec<_> = passes.iter().map(|mk_pass| (mk_pass)()).collect();
405 passes.push(Box::new(builtin_lints));
406 let pass = RuntimeCombinedEarlyLintPass { passes: &mut passes[..] };
407 check_ast_node_inner(sess, check_node, context, pass);
411 pub fn check_ast_node_inner<'a, T: EarlyLintPass>(
413 check_node: impl EarlyCheckNode<'a>,
414 context: EarlyContext<'_>,
417 let mut cx = EarlyContextAndPass { context, pass };
419 cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
421 // All of the buffered lints should have been emitted at this point.
422 // If not, that means that we somehow buffered a lint for a node id
423 // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
424 for (id, lints) in cx.context.buffered.map {
425 for early_lint in lints {
429 "failed to process buffered lint here (dummy = {})",
430 id == ast::DUMMY_NODE_ID