rustc_lint/
early.rs

1//! Implementation of the early lint pass.
2//!
3//! The early lint pass works on AST nodes after macro expansion and name
4//! resolution, just before AST lowering. These lints are for purely
5//! syntactical lints.
6
7use rustc_ast::ptr::P;
8use rustc_ast::visit::{self as ast_visit, Visitor, walk_list};
9use rustc_ast::{self as ast, HasAttrs};
10use rustc_data_structures::stack::ensure_sufficient_stack;
11use rustc_feature::Features;
12use rustc_middle::ty::{RegisteredTools, TyCtxt};
13use rustc_session::Session;
14use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
15use rustc_span::{Ident, Span};
16use tracing::debug;
17
18use crate::context::{EarlyContext, LintContext, LintStore};
19use crate::passes::{EarlyLintPass, EarlyLintPassObject};
20
21mod diagnostics;
22
23macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
24    $cx.pass.$f(&$cx.context, $($args),*);
25}) }
26
27/// Implements the AST traversal for early lint passes. `T` provides the
28/// `check_*` methods.
29pub struct EarlyContextAndPass<'ecx, 'tcx, T: EarlyLintPass> {
30    context: EarlyContext<'ecx>,
31    tcx: Option<TyCtxt<'tcx>>,
32    pass: T,
33}
34
35impl<'ecx, 'tcx, T: EarlyLintPass> EarlyContextAndPass<'ecx, 'tcx, T> {
36    // This always-inlined function is for the hot call site.
37    #[inline(always)]
38    #[allow(rustc::diagnostic_outside_of_impl)]
39    fn inlined_check_id(&mut self, id: ast::NodeId) {
40        for early_lint in self.context.buffered.take(id) {
41            let BufferedEarlyLint { span, node_id: _, lint_id, diagnostic } = early_lint;
42            self.context.opt_span_lint(lint_id.lint, span, |diag| {
43                diagnostics::decorate_lint(self.context.sess(), self.tcx, diagnostic, diag);
44            });
45        }
46    }
47
48    // This non-inlined function is for the cold call sites.
49    fn check_id(&mut self, id: ast::NodeId) {
50        self.inlined_check_id(id)
51    }
52
53    /// Merge the lints specified by any lint attributes into the
54    /// current lint context, call the provided function, then reset the
55    /// lints in effect to their previous state.
56    fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'_ [ast::Attribute], f: F)
57    where
58        F: FnOnce(&mut Self),
59    {
60        let is_crate_node = id == ast::CRATE_NODE_ID;
61        debug!(?id);
62        let push = self.context.builder.push(attrs, is_crate_node, None);
63
64        self.inlined_check_id(id);
65        debug!("early context: enter_attrs({:?})", attrs);
66        lint_callback!(self, check_attributes, attrs);
67        ensure_sufficient_stack(|| f(self));
68        debug!("early context: exit_attrs({:?})", attrs);
69        lint_callback!(self, check_attributes_post, attrs);
70        self.context.builder.pop(push);
71    }
72}
73
74impl<'ast, 'ecx, 'tcx, T: EarlyLintPass> ast_visit::Visitor<'ast>
75    for EarlyContextAndPass<'ecx, 'tcx, T>
76{
77    fn visit_coroutine_kind(&mut self, coroutine_kind: &'ast ast::CoroutineKind) -> Self::Result {
78        self.check_id(coroutine_kind.closure_id());
79    }
80
81    fn visit_param(&mut self, param: &'ast ast::Param) {
82        self.with_lint_attrs(param.id, &param.attrs, |cx| {
83            lint_callback!(cx, check_param, param);
84            ast_visit::walk_param(cx, param);
85        });
86    }
87
88    fn visit_item(&mut self, it: &'ast ast::Item) {
89        self.with_lint_attrs(it.id, &it.attrs, |cx| {
90            lint_callback!(cx, check_item, it);
91            ast_visit::walk_item(cx, it);
92            lint_callback!(cx, check_item_post, it);
93        })
94    }
95
96    fn visit_foreign_item(&mut self, it: &'ast ast::ForeignItem) {
97        self.with_lint_attrs(it.id, &it.attrs, |cx| {
98            ast_visit::walk_item(cx, it);
99        })
100    }
101
102    fn visit_pat(&mut self, p: &'ast ast::Pat) {
103        lint_callback!(self, check_pat, p);
104        self.check_id(p.id);
105        ast_visit::walk_pat(self, p);
106        lint_callback!(self, check_pat_post, p);
107    }
108
109    fn visit_pat_field(&mut self, field: &'ast ast::PatField) {
110        self.with_lint_attrs(field.id, &field.attrs, |cx| {
111            ast_visit::walk_pat_field(cx, field);
112        });
113    }
114
115    fn visit_anon_const(&mut self, c: &'ast ast::AnonConst) {
116        self.check_id(c.id);
117        ast_visit::walk_anon_const(self, c);
118    }
119
120    fn visit_expr(&mut self, e: &'ast ast::Expr) {
121        self.with_lint_attrs(e.id, &e.attrs, |cx| {
122            lint_callback!(cx, check_expr, e);
123            ast_visit::walk_expr(cx, e);
124            lint_callback!(cx, check_expr_post, e);
125        })
126    }
127
128    fn visit_expr_field(&mut self, f: &'ast ast::ExprField) {
129        self.with_lint_attrs(f.id, &f.attrs, |cx| {
130            ast_visit::walk_expr_field(cx, f);
131        })
132    }
133
134    fn visit_stmt(&mut self, s: &'ast 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
140        //
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);
145            cx.check_id(s.id);
146        });
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);
152    }
153
154    fn visit_fn(&mut self, fk: ast_visit::FnKind<'ast>, span: Span, id: ast::NodeId) {
155        lint_callback!(self, check_fn, fk, span, id);
156        self.check_id(id);
157        ast_visit::walk_fn(self, fk);
158    }
159
160    fn visit_variant_data(&mut self, s: &'ast ast::VariantData) {
161        if let Some(ctor_node_id) = s.ctor_node_id() {
162            self.check_id(ctor_node_id);
163        }
164        ast_visit::walk_struct_def(self, s);
165    }
166
167    fn visit_field_def(&mut self, s: &'ast ast::FieldDef) {
168        self.with_lint_attrs(s.id, &s.attrs, |cx| {
169            ast_visit::walk_field_def(cx, s);
170        })
171    }
172
173    fn visit_variant(&mut self, v: &'ast ast::Variant) {
174        self.with_lint_attrs(v.id, &v.attrs, |cx| {
175            lint_callback!(cx, check_variant, v);
176            ast_visit::walk_variant(cx, v);
177        })
178    }
179
180    fn visit_ty(&mut self, t: &'ast ast::Ty) {
181        lint_callback!(self, check_ty, t);
182        self.check_id(t.id);
183        ast_visit::walk_ty(self, t);
184    }
185
186    fn visit_ident(&mut self, ident: &Ident) {
187        lint_callback!(self, check_ident, ident);
188    }
189
190    fn visit_local(&mut self, l: &'ast ast::Local) {
191        self.with_lint_attrs(l.id, &l.attrs, |cx| {
192            lint_callback!(cx, check_local, l);
193            ast_visit::walk_local(cx, l);
194        })
195    }
196
197    fn visit_block(&mut self, b: &'ast ast::Block) {
198        lint_callback!(self, check_block, b);
199        self.check_id(b.id);
200        ast_visit::walk_block(self, b);
201    }
202
203    fn visit_arm(&mut self, a: &'ast ast::Arm) {
204        self.with_lint_attrs(a.id, &a.attrs, |cx| {
205            lint_callback!(cx, check_arm, a);
206            ast_visit::walk_arm(cx, a);
207        })
208    }
209
210    fn visit_generic_arg(&mut self, arg: &'ast ast::GenericArg) {
211        lint_callback!(self, check_generic_arg, arg);
212        ast_visit::walk_generic_arg(self, arg);
213    }
214
215    fn visit_generic_param(&mut self, param: &'ast ast::GenericParam) {
216        self.with_lint_attrs(param.id, &param.attrs, |cx| {
217            lint_callback!(cx, check_generic_param, param);
218            ast_visit::walk_generic_param(cx, param);
219        });
220    }
221
222    fn visit_generics(&mut self, g: &'ast ast::Generics) {
223        lint_callback!(self, check_generics, g);
224        ast_visit::walk_generics(self, g);
225    }
226
227    fn visit_where_predicate(&mut self, p: &'ast ast::WherePredicate) {
228        lint_callback!(self, enter_where_predicate, p);
229        ast_visit::walk_where_predicate(self, p);
230        lint_callback!(self, exit_where_predicate, p);
231    }
232
233    fn visit_poly_trait_ref(&mut self, t: &'ast ast::PolyTraitRef) {
234        lint_callback!(self, check_poly_trait_ref, t);
235        ast_visit::walk_poly_trait_ref(self, t);
236    }
237
238    fn visit_assoc_item(&mut self, item: &'ast ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
239        self.with_lint_attrs(item.id, &item.attrs, |cx| {
240            match ctxt {
241                ast_visit::AssocCtxt::Trait => {
242                    lint_callback!(cx, check_trait_item, item);
243                }
244                ast_visit::AssocCtxt::Impl => {
245                    lint_callback!(cx, check_impl_item, item);
246                }
247            }
248            ast_visit::walk_assoc_item(cx, item, ctxt);
249            match ctxt {
250                ast_visit::AssocCtxt::Trait => {
251                    lint_callback!(cx, check_trait_item_post, item);
252                }
253                ast_visit::AssocCtxt::Impl => {
254                    lint_callback!(cx, check_impl_item_post, item);
255                }
256            }
257        });
258    }
259
260    fn visit_lifetime(&mut self, lt: &'ast ast::Lifetime, _: ast_visit::LifetimeCtxt) {
261        self.check_id(lt.id);
262        ast_visit::walk_lifetime(self, lt);
263    }
264
265    fn visit_path(&mut self, p: &'ast ast::Path, id: ast::NodeId) {
266        self.check_id(id);
267        ast_visit::walk_path(self, p);
268    }
269
270    fn visit_path_segment(&mut self, s: &'ast ast::PathSegment) {
271        self.check_id(s.id);
272        ast_visit::walk_path_segment(self, s);
273    }
274
275    fn visit_attribute(&mut self, attr: &'ast ast::Attribute) {
276        lint_callback!(self, check_attribute, attr);
277        ast_visit::walk_attribute(self, attr);
278    }
279
280    fn visit_mac_def(&mut self, mac: &'ast ast::MacroDef, id: ast::NodeId) {
281        lint_callback!(self, check_mac_def, mac);
282        self.check_id(id);
283    }
284
285    fn visit_mac_call(&mut self, mac: &'ast ast::MacCall) {
286        lint_callback!(self, check_mac, mac);
287        ast_visit::walk_mac(self, mac);
288    }
289}
290
291// Combines multiple lint passes into a single pass, at runtime. Each
292// `check_foo` method in `$methods` within this pass simply calls `check_foo`
293// once per `$pass`. Compare with `declare_combined_early_lint_pass`, which is
294// similar, but combines lint passes at compile time.
295struct RuntimeCombinedEarlyLintPass<'a> {
296    passes: &'a mut [EarlyLintPassObject],
297}
298
299#[allow(rustc::lint_pass_impl_without_macro)]
300impl LintPass for RuntimeCombinedEarlyLintPass<'_> {
301    fn name(&self) -> &'static str {
302        panic!()
303    }
304    fn get_lints(&self) -> crate::LintVec {
305        panic!()
306    }
307}
308
309macro_rules! impl_early_lint_pass {
310    ([], [$($(#[$attr:meta])* fn $f:ident($($param:ident: $arg:ty),*);)*]) => (
311        impl EarlyLintPass for RuntimeCombinedEarlyLintPass<'_> {
312            $(fn $f(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
313                for pass in self.passes.iter_mut() {
314                    pass.$f(context, $($param),*);
315                }
316            })*
317        }
318    )
319}
320
321crate::early_lint_methods!(impl_early_lint_pass, []);
322
323/// Early lints work on different nodes - either on the crate root, or on freshly loaded modules.
324/// This trait generalizes over those nodes.
325pub trait EarlyCheckNode<'a>: Copy {
326    fn id(self) -> ast::NodeId;
327    fn attrs(self) -> &'a [ast::Attribute];
328    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>);
329}
330
331impl<'a> EarlyCheckNode<'a> for (&'a ast::Crate, &'a [ast::Attribute]) {
332    fn id(self) -> ast::NodeId {
333        ast::CRATE_NODE_ID
334    }
335    fn attrs(self) -> &'a [ast::Attribute] {
336        self.1
337    }
338    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>) {
339        lint_callback!(cx, check_crate, self.0);
340        ast_visit::walk_crate(cx, self.0);
341        lint_callback!(cx, check_crate_post, self.0);
342    }
343}
344
345impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
346    fn id(self) -> ast::NodeId {
347        self.0
348    }
349    fn attrs(self) -> &'a [ast::Attribute] {
350        self.1
351    }
352    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>) {
353        walk_list!(cx, visit_attribute, self.1);
354        walk_list!(cx, visit_item, self.2);
355    }
356}
357
358pub fn check_ast_node<'a>(
359    sess: &Session,
360    tcx: Option<TyCtxt<'_>>,
361    features: &Features,
362    pre_expansion: bool,
363    lint_store: &LintStore,
364    registered_tools: &RegisteredTools,
365    lint_buffer: Option<LintBuffer>,
366    builtin_lints: impl EarlyLintPass + 'static,
367    check_node: impl EarlyCheckNode<'a>,
368) {
369    let context = EarlyContext::new(
370        sess,
371        features,
372        !pre_expansion,
373        lint_store,
374        registered_tools,
375        lint_buffer.unwrap_or_default(),
376    );
377
378    // Note: `passes` is often empty. In that case, it's faster to run
379    // `builtin_lints` directly rather than bundling it up into the
380    // `RuntimeCombinedEarlyLintPass`.
381    let passes =
382        if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
383    if passes.is_empty() {
384        check_ast_node_inner(sess, tcx, check_node, context, builtin_lints);
385    } else {
386        let mut passes: Vec<_> = passes.iter().map(|mk_pass| (mk_pass)()).collect();
387        passes.push(Box::new(builtin_lints));
388        let pass = RuntimeCombinedEarlyLintPass { passes: &mut passes[..] };
389        check_ast_node_inner(sess, tcx, check_node, context, pass);
390    }
391}
392
393fn check_ast_node_inner<'a, T: EarlyLintPass>(
394    sess: &Session,
395    tcx: Option<TyCtxt<'_>>,
396    check_node: impl EarlyCheckNode<'a>,
397    context: EarlyContext<'_>,
398    pass: T,
399) {
400    let mut cx = EarlyContextAndPass { context, tcx, pass };
401
402    cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
403
404    // All of the buffered lints should have been emitted at this point.
405    // If not, that means that we somehow buffered a lint for a node id
406    // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
407    for (id, lints) in cx.context.buffered.map {
408        if !lints.is_empty() {
409            assert!(
410                sess.dcx().has_errors().is_some(),
411                "failed to process buffered lint here (dummy = {})",
412                id == ast::DUMMY_NODE_ID
413            );
414            break;
415        }
416    }
417}