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
21pub(super) mod 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_builtin_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_id(&mut self, id: rustc_ast::NodeId) {
78        self.check_id(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        ast_visit::walk_pat(self, p);
105        lint_callback!(self, check_pat_post, p);
106    }
107
108    fn visit_pat_field(&mut self, field: &'ast ast::PatField) {
109        self.with_lint_attrs(field.id, &field.attrs, |cx| {
110            ast_visit::walk_pat_field(cx, field);
111        });
112    }
113
114    fn visit_expr(&mut self, e: &'ast ast::Expr) {
115        self.with_lint_attrs(e.id, &e.attrs, |cx| {
116            lint_callback!(cx, check_expr, e);
117            ast_visit::walk_expr(cx, e);
118            lint_callback!(cx, check_expr_post, e);
119        })
120    }
121
122    fn visit_expr_field(&mut self, f: &'ast ast::ExprField) {
123        self.with_lint_attrs(f.id, &f.attrs, |cx| {
124            ast_visit::walk_expr_field(cx, f);
125        })
126    }
127
128    fn visit_stmt(&mut self, s: &'ast ast::Stmt) {
129        // Add the statement's lint attributes to our
130        // current state when checking the statement itself.
131        // This allows us to handle attributes like
132        // `#[allow(unused_doc_comments)]`, which apply to
133        // sibling attributes on the same target
134        //
135        // Note that statements get their attributes from
136        // the AST struct that they wrap (e.g. an item)
137        self.with_lint_attrs(s.id, s.attrs(), |cx| {
138            lint_callback!(cx, check_stmt, s);
139            cx.check_id(s.id);
140        });
141        // The visitor for the AST struct wrapped
142        // by the statement (e.g. `Item`) will call
143        // `with_lint_attrs`, so do this walk
144        // outside of the above `with_lint_attrs` call
145        ast_visit::walk_stmt(self, s);
146    }
147
148    fn visit_fn(&mut self, fk: ast_visit::FnKind<'ast>, span: Span, id: ast::NodeId) {
149        lint_callback!(self, check_fn, fk, span, id);
150        self.check_id(id);
151        ast_visit::walk_fn(self, fk);
152    }
153
154    fn visit_field_def(&mut self, s: &'ast ast::FieldDef) {
155        self.with_lint_attrs(s.id, &s.attrs, |cx| {
156            ast_visit::walk_field_def(cx, s);
157        })
158    }
159
160    fn visit_variant(&mut self, v: &'ast ast::Variant) {
161        self.with_lint_attrs(v.id, &v.attrs, |cx| {
162            lint_callback!(cx, check_variant, v);
163            ast_visit::walk_variant(cx, v);
164        })
165    }
166
167    fn visit_ty(&mut self, t: &'ast ast::Ty) {
168        lint_callback!(self, check_ty, t);
169        ast_visit::walk_ty(self, t);
170    }
171
172    fn visit_ident(&mut self, ident: &Ident) {
173        lint_callback!(self, check_ident, ident);
174    }
175
176    fn visit_local(&mut self, l: &'ast ast::Local) {
177        self.with_lint_attrs(l.id, &l.attrs, |cx| {
178            lint_callback!(cx, check_local, l);
179            ast_visit::walk_local(cx, l);
180        })
181    }
182
183    fn visit_block(&mut self, b: &'ast ast::Block) {
184        lint_callback!(self, check_block, b);
185        ast_visit::walk_block(self, b);
186    }
187
188    fn visit_arm(&mut self, a: &'ast ast::Arm) {
189        self.with_lint_attrs(a.id, &a.attrs, |cx| {
190            lint_callback!(cx, check_arm, a);
191            ast_visit::walk_arm(cx, a);
192        })
193    }
194
195    fn visit_generic_arg(&mut self, arg: &'ast ast::GenericArg) {
196        lint_callback!(self, check_generic_arg, arg);
197        ast_visit::walk_generic_arg(self, arg);
198    }
199
200    fn visit_generic_param(&mut self, param: &'ast ast::GenericParam) {
201        self.with_lint_attrs(param.id, &param.attrs, |cx| {
202            lint_callback!(cx, check_generic_param, param);
203            ast_visit::walk_generic_param(cx, param);
204        });
205    }
206
207    fn visit_generics(&mut self, g: &'ast ast::Generics) {
208        lint_callback!(self, check_generics, g);
209        ast_visit::walk_generics(self, g);
210    }
211
212    fn visit_where_predicate(&mut self, p: &'ast ast::WherePredicate) {
213        lint_callback!(self, enter_where_predicate, p);
214        ast_visit::walk_where_predicate(self, p);
215        lint_callback!(self, exit_where_predicate, p);
216    }
217
218    fn visit_poly_trait_ref(&mut self, t: &'ast ast::PolyTraitRef) {
219        lint_callback!(self, check_poly_trait_ref, t);
220        ast_visit::walk_poly_trait_ref(self, t);
221    }
222
223    fn visit_assoc_item(&mut self, item: &'ast ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
224        self.with_lint_attrs(item.id, &item.attrs, |cx| {
225            match ctxt {
226                ast_visit::AssocCtxt::Trait => {
227                    lint_callback!(cx, check_trait_item, item);
228                }
229                ast_visit::AssocCtxt::Impl { .. } => {
230                    lint_callback!(cx, check_impl_item, item);
231                }
232            }
233            ast_visit::walk_assoc_item(cx, item, ctxt);
234            match ctxt {
235                ast_visit::AssocCtxt::Trait => {
236                    lint_callback!(cx, check_trait_item_post, item);
237                }
238                ast_visit::AssocCtxt::Impl { .. } => {
239                    lint_callback!(cx, check_impl_item_post, item);
240                }
241            }
242        });
243    }
244
245    fn visit_attribute(&mut self, attr: &'ast ast::Attribute) {
246        lint_callback!(self, check_attribute, attr);
247        ast_visit::walk_attribute(self, attr);
248    }
249
250    fn visit_macro_def(&mut self, mac: &'ast ast::MacroDef) {
251        lint_callback!(self, check_mac_def, mac);
252    }
253
254    fn visit_mac_call(&mut self, mac: &'ast ast::MacCall) {
255        lint_callback!(self, check_mac, mac);
256        ast_visit::walk_mac(self, mac);
257    }
258}
259
260// Combines multiple lint passes into a single pass, at runtime. Each
261// `check_foo` method in `$methods` within this pass simply calls `check_foo`
262// once per `$pass`. Compare with `declare_combined_early_lint_pass`, which is
263// similar, but combines lint passes at compile time.
264struct RuntimeCombinedEarlyLintPass<'a> {
265    passes: &'a mut [EarlyLintPassObject],
266}
267
268#[allow(rustc::lint_pass_impl_without_macro)]
269impl LintPass for RuntimeCombinedEarlyLintPass<'_> {
270    fn name(&self) -> &'static str {
271        panic!()
272    }
273    fn get_lints(&self) -> crate::LintVec {
274        panic!()
275    }
276}
277
278macro_rules! impl_early_lint_pass {
279    ([], [$($(#[$attr:meta])* fn $f:ident($($param:ident: $arg:ty),*);)*]) => (
280        impl EarlyLintPass for RuntimeCombinedEarlyLintPass<'_> {
281            $(fn $f(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
282                for pass in self.passes.iter_mut() {
283                    pass.$f(context, $($param),*);
284                }
285            })*
286        }
287    )
288}
289
290crate::early_lint_methods!(impl_early_lint_pass, []);
291
292/// Early lints work on different nodes - either on the crate root, or on freshly loaded modules.
293/// This trait generalizes over those nodes.
294pub trait EarlyCheckNode<'a>: Copy {
295    fn id(self) -> ast::NodeId;
296    fn attrs(self) -> &'a [ast::Attribute];
297    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>);
298}
299
300impl<'a> EarlyCheckNode<'a> for (&'a ast::Crate, &'a [ast::Attribute]) {
301    fn id(self) -> ast::NodeId {
302        ast::CRATE_NODE_ID
303    }
304    fn attrs(self) -> &'a [ast::Attribute] {
305        self.1
306    }
307    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>) {
308        lint_callback!(cx, check_crate, self.0);
309        ast_visit::walk_crate(cx, self.0);
310        lint_callback!(cx, check_crate_post, self.0);
311    }
312}
313
314impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
315    fn id(self) -> ast::NodeId {
316        self.0
317    }
318    fn attrs(self) -> &'a [ast::Attribute] {
319        self.1
320    }
321    fn check<'ecx, 'tcx, T: EarlyLintPass>(self, cx: &mut EarlyContextAndPass<'ecx, 'tcx, T>) {
322        walk_list!(cx, visit_attribute, self.1);
323        walk_list!(cx, visit_item, self.2);
324    }
325}
326
327pub fn check_ast_node<'a>(
328    sess: &Session,
329    tcx: Option<TyCtxt<'_>>,
330    features: &Features,
331    pre_expansion: bool,
332    lint_store: &LintStore,
333    registered_tools: &RegisteredTools,
334    lint_buffer: Option<LintBuffer>,
335    builtin_lints: impl EarlyLintPass + 'static,
336    check_node: impl EarlyCheckNode<'a>,
337) {
338    let context = EarlyContext::new(
339        sess,
340        features,
341        !pre_expansion,
342        lint_store,
343        registered_tools,
344        lint_buffer.unwrap_or_default(),
345    );
346
347    // Note: `passes` is often empty. In that case, it's faster to run
348    // `builtin_lints` directly rather than bundling it up into the
349    // `RuntimeCombinedEarlyLintPass`.
350    let passes =
351        if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
352    if passes.is_empty() {
353        check_ast_node_inner(sess, tcx, check_node, context, builtin_lints);
354    } else {
355        let mut passes: Vec<_> = passes.iter().map(|mk_pass| (mk_pass)()).collect();
356        passes.push(Box::new(builtin_lints));
357        let pass = RuntimeCombinedEarlyLintPass { passes: &mut passes[..] };
358        check_ast_node_inner(sess, tcx, check_node, context, pass);
359    }
360}
361
362fn check_ast_node_inner<'a, T: EarlyLintPass>(
363    sess: &Session,
364    tcx: Option<TyCtxt<'_>>,
365    check_node: impl EarlyCheckNode<'a>,
366    context: EarlyContext<'_>,
367    pass: T,
368) {
369    let mut cx = EarlyContextAndPass { context, tcx, pass };
370
371    cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
372
373    // All of the buffered lints should have been emitted at this point.
374    // If not, that means that we somehow buffered a lint for a node id
375    // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
376    for (id, lints) in cx.context.buffered.map {
377        if !lints.is_empty() {
378            assert!(
379                sess.dcx().has_errors().is_some(),
380                "failed to process buffered lint here (dummy = {})",
381                id == ast::DUMMY_NODE_ID
382            );
383            break;
384        }
385    }
386}