compiler/rustc_lint/src/early.rs

   1 //! Implementation of lint checking.
   2 //!
   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.
   9 //!
  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.
  16
  17 use crate::context::{EarlyContext, LintContext, LintStore};
  18 use crate::passes::{EarlyLintPass, EarlyLintPassObject};
  19 use rustc_ast as ast;
  20 use rustc_ast::visit as ast_visit;
  21 use rustc_session::lint::{BufferedEarlyLint, LintBuffer, LintPass};
  22 use rustc_session::Session;
  23 use rustc_span::symbol::Ident;
  24 use rustc_span::Span;
  25
  26 use std::slice;
  27 use tracing::debug;
  28
  29 macro_rules! run_early_pass { ($cx:expr, $f:ident, $($args:expr),*) => ({
  30     $cx.pass.$f(&$cx.context, $($args),*);
  31 }) }
  32
  33 struct EarlyContextAndPass<'a, T: EarlyLintPass> {
  34     context: EarlyContext<'a>,
  35     pass: T,
  36 }
  37
  38 impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
  39     fn check_id(&mut self, id: ast::NodeId) {
  40         for early_lint in self.context.buffered.take(id) {
  41             let BufferedEarlyLint { span, msg, node_id: _, lint_id, diagnostic } = early_lint;
  42             self.context.lookup_with_diagnostics(
  43                 lint_id.lint,
  44                 Some(span),
  45                 |lint| lint.build(&msg).emit(),
  46                 diagnostic,
  47             );
  48         }
  49     }
  50
  51     /// Merge the lints specified by any lint attributes into the
  52     /// current lint context, call the provided function, then reset the
  53     /// lints in effect to their previous state.
  54     fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'a [ast::Attribute], f: F)
  55     where
  56         F: FnOnce(&mut Self),
  57     {
  58         let is_crate_node = id == ast::CRATE_NODE_ID;
  59         let push = self.context.builder.push(attrs, &self.context.lint_store, is_crate_node);
  60         self.check_id(id);
  61         self.enter_attrs(attrs);
  62         f(self);
  63         self.exit_attrs(attrs);
  64         self.context.builder.pop(push);
  65     }
  66
  67     fn enter_attrs(&mut self, attrs: &'a [ast::Attribute]) {
  68         debug!("early context: enter_attrs({:?})", attrs);
  69         run_early_pass!(self, enter_lint_attrs, attrs);
  70     }
  71
  72     fn exit_attrs(&mut self, attrs: &'a [ast::Attribute]) {
  73         debug!("early context: exit_attrs({:?})", attrs);
  74         run_early_pass!(self, exit_lint_attrs, attrs);
  75     }
  76 }
  77
  78 impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T> {
  79     fn visit_param(&mut self, param: &'a ast::Param) {
  80         self.with_lint_attrs(param.id, &param.attrs, |cx| {
  81             run_early_pass!(cx, check_param, param);
  82             ast_visit::walk_param(cx, param);
  83         });
  84     }
  85
  86     fn visit_item(&mut self, it: &'a ast::Item) {
  87         self.with_lint_attrs(it.id, &it.attrs, |cx| {
  88             run_early_pass!(cx, check_item, it);
  89             ast_visit::walk_item(cx, it);
  90             run_early_pass!(cx, check_item_post, it);
  91         })
  92     }
  93
  94     fn visit_foreign_item(&mut self, it: &'a ast::ForeignItem) {
  95         self.with_lint_attrs(it.id, &it.attrs, |cx| {
  96             run_early_pass!(cx, check_foreign_item, it);
  97             ast_visit::walk_foreign_item(cx, it);
  98             run_early_pass!(cx, check_foreign_item_post, it);
  99         })
 100     }
 101
 102     fn visit_pat(&mut self, p: &'a ast::Pat) {
 103         run_early_pass!(self, check_pat, p);
 104         self.check_id(p.id);
 105         ast_visit::walk_pat(self, p);
 106         run_early_pass!(self, check_pat_post, p);
 107     }
 108
 109     fn visit_anon_const(&mut self, c: &'a ast::AnonConst) {
 110         run_early_pass!(self, check_anon_const, c);
 111         ast_visit::walk_anon_const(self, c);
 112     }
 113
 114     fn visit_expr(&mut self, e: &'a ast::Expr) {
 115         self.with_lint_attrs(e.id, &e.attrs, |cx| {
 116             run_early_pass!(cx, check_expr, e);
 117             ast_visit::walk_expr(cx, e);
 118         })
 119     }
 120
 121     fn visit_stmt(&mut self, s: &'a ast::Stmt) {
 122         run_early_pass!(self, check_stmt, s);
 123         self.check_id(s.id);
 124         ast_visit::walk_stmt(self, s);
 125     }
 126
 127     fn visit_fn(&mut self, fk: ast_visit::FnKind<'a>, span: Span, id: ast::NodeId) {
 128         run_early_pass!(self, check_fn, fk, span, id);
 129         self.check_id(id);
 130         ast_visit::walk_fn(self, fk, span);
 131         run_early_pass!(self, check_fn_post, fk, span, id);
 132     }
 133
 134     fn visit_variant_data(&mut self, s: &'a ast::VariantData) {
 135         run_early_pass!(self, check_struct_def, s);
 136         if let Some(ctor_hir_id) = s.ctor_id() {
 137             self.check_id(ctor_hir_id);
 138         }
 139         ast_visit::walk_struct_def(self, s);
 140         run_early_pass!(self, check_struct_def_post, s);
 141     }
 142
 143     fn visit_struct_field(&mut self, s: &'a ast::StructField) {
 144         self.with_lint_attrs(s.id, &s.attrs, |cx| {
 145             run_early_pass!(cx, check_struct_field, s);
 146             ast_visit::walk_struct_field(cx, s);
 147         })
 148     }
 149
 150     fn visit_variant(&mut self, v: &'a ast::Variant) {
 151         self.with_lint_attrs(v.id, &v.attrs, |cx| {
 152             run_early_pass!(cx, check_variant, v);
 153             ast_visit::walk_variant(cx, v);
 154             run_early_pass!(cx, check_variant_post, v);
 155         })
 156     }
 157
 158     fn visit_ty(&mut self, t: &'a ast::Ty) {
 159         run_early_pass!(self, check_ty, t);
 160         self.check_id(t.id);
 161         ast_visit::walk_ty(self, t);
 162     }
 163
 164     fn visit_ident(&mut self, ident: Ident) {
 165         run_early_pass!(self, check_ident, ident);
 166     }
 167
 168     fn visit_mod(&mut self, m: &'a ast::Mod, s: Span, _a: &[ast::Attribute], n: ast::NodeId) {
 169         run_early_pass!(self, check_mod, m, s, n);
 170         self.check_id(n);
 171         ast_visit::walk_mod(self, m);
 172         run_early_pass!(self, check_mod_post, m, s, n);
 173     }
 174
 175     fn visit_local(&mut self, l: &'a ast::Local) {
 176         self.with_lint_attrs(l.id, &l.attrs, |cx| {
 177             run_early_pass!(cx, check_local, l);
 178             ast_visit::walk_local(cx, l);
 179         })
 180     }
 181
 182     fn visit_block(&mut self, b: &'a ast::Block) {
 183         run_early_pass!(self, check_block, b);
 184         self.check_id(b.id);
 185         ast_visit::walk_block(self, b);
 186         run_early_pass!(self, check_block_post, b);
 187     }
 188
 189     fn visit_arm(&mut self, a: &'a ast::Arm) {
 190         run_early_pass!(self, check_arm, a);
 191         ast_visit::walk_arm(self, a);
 192     }
 193
 194     fn visit_expr_post(&mut self, e: &'a ast::Expr) {
 195         run_early_pass!(self, check_expr_post, e);
 196     }
 197
 198     fn visit_generic_param(&mut self, param: &'a ast::GenericParam) {
 199         run_early_pass!(self, check_generic_param, param);
 200         ast_visit::walk_generic_param(self, param);
 201     }
 202
 203     fn visit_generics(&mut self, g: &'a ast::Generics) {
 204         run_early_pass!(self, check_generics, g);
 205         ast_visit::walk_generics(self, g);
 206     }
 207
 208     fn visit_where_predicate(&mut self, p: &'a ast::WherePredicate) {
 209         run_early_pass!(self, check_where_predicate, p);
 210         ast_visit::walk_where_predicate(self, p);
 211     }
 212
 213     fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef, m: &'a ast::TraitBoundModifier) {
 214         run_early_pass!(self, check_poly_trait_ref, t, m);
 215         ast_visit::walk_poly_trait_ref(self, t, m);
 216     }
 217
 218     fn visit_assoc_item(&mut self, item: &'a ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
 219         self.with_lint_attrs(item.id, &item.attrs, |cx| match ctxt {
 220             ast_visit::AssocCtxt::Trait => {
 221                 run_early_pass!(cx, check_trait_item, item);
 222                 ast_visit::walk_assoc_item(cx, item, ctxt);
 223                 run_early_pass!(cx, check_trait_item_post, item);
 224             }
 225             ast_visit::AssocCtxt::Impl => {
 226                 run_early_pass!(cx, check_impl_item, item);
 227                 ast_visit::walk_assoc_item(cx, item, ctxt);
 228                 run_early_pass!(cx, check_impl_item_post, item);
 229             }
 230         });
 231     }
 232
 233     fn visit_lifetime(&mut self, lt: &'a ast::Lifetime) {
 234         run_early_pass!(self, check_lifetime, lt);
 235         self.check_id(lt.id);
 236     }
 237
 238     fn visit_path(&mut self, p: &'a ast::Path, id: ast::NodeId) {
 239         run_early_pass!(self, check_path, p, id);
 240         self.check_id(id);
 241         ast_visit::walk_path(self, p);
 242     }
 243
 244     fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
 245         run_early_pass!(self, check_attribute, attr);
 246     }
 247
 248     fn visit_mac_def(&mut self, mac: &'a ast::MacroDef, id: ast::NodeId) {
 249         run_early_pass!(self, check_mac_def, mac, id);
 250         self.check_id(id);
 251     }
 252
 253     fn visit_mac(&mut self, mac: &'a ast::MacCall) {
 254         // FIXME(#54110): So, this setup isn't really right. I think
 255         // that (a) the librustc_ast visitor ought to be doing this as
 256         // part of `walk_mac`, and (b) we should be calling
 257         // `visit_path`, *but* that would require a `NodeId`, and I
 258         // want to get #53686 fixed quickly. -nmatsakis
 259         ast_visit::walk_path(self, &mac.path);
 260
 261         run_early_pass!(self, check_mac, mac);
 262     }
 263 }
 264
 265 struct EarlyLintPassObjects<'a> {
 266     lints: &'a mut [EarlyLintPassObject],
 267 }
 268
 269 #[allow(rustc::lint_pass_impl_without_macro)]
 270 impl LintPass for EarlyLintPassObjects<'_> {
 271     fn name(&self) -> &'static str {
 272         panic!()
 273     }
 274 }
 275
 276 macro_rules! expand_early_lint_pass_impl_methods {
 277     ([$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 278         $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
 279             for obj in self.lints.iter_mut() {
 280                 obj.$name(context, $($param),*);
 281             }
 282         })*
 283     )
 284 }
 285
 286 macro_rules! early_lint_pass_impl {
 287     ([], [$($methods:tt)*]) => (
 288         impl EarlyLintPass for EarlyLintPassObjects<'_> {
 289             expand_early_lint_pass_impl_methods!([$($methods)*]);
 290         }
 291     )
 292 }
 293
 294 crate::early_lint_methods!(early_lint_pass_impl, []);
 295
 296 fn early_lint_crate<T: EarlyLintPass>(
 297     sess: &Session,
 298     lint_store: &LintStore,
 299     krate: &ast::Crate,
 300     pass: T,
 301     buffered: LintBuffer,
 302     warn_about_weird_lints: bool,
 303 ) -> LintBuffer {
 304     let mut cx = EarlyContextAndPass {
 305         context: EarlyContext::new(sess, lint_store, krate, buffered, warn_about_weird_lints),
 306         pass,
 307     };
 308
 309     // Visit the whole crate.
 310     cx.with_lint_attrs(ast::CRATE_NODE_ID, &krate.attrs, |cx| {
 311         // since the root module isn't visited as an item (because it isn't an
 312         // item), warn for it here.
 313         run_early_pass!(cx, check_crate, krate);
 314
 315         ast_visit::walk_crate(cx, krate);
 316
 317         run_early_pass!(cx, check_crate_post, krate);
 318     });
 319     cx.context.buffered
 320 }
 321
 322 pub fn check_ast_crate<T: EarlyLintPass>(
 323     sess: &Session,
 324     lint_store: &LintStore,
 325     krate: &ast::Crate,
 326     pre_expansion: bool,
 327     lint_buffer: Option<LintBuffer>,
 328     builtin_lints: T,
 329 ) {
 330     let passes =
 331         if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
 332     let mut passes: Vec<_> = passes.iter().map(|p| (p)()).collect();
 333     let mut buffered = lint_buffer.unwrap_or_default();
 334
 335     if !sess.opts.debugging_opts.no_interleave_lints {
 336         buffered =
 337             early_lint_crate(sess, lint_store, krate, builtin_lints, buffered, pre_expansion);
 338
 339         if !passes.is_empty() {
 340             buffered = early_lint_crate(
 341                 sess,
 342                 lint_store,
 343                 krate,
 344                 EarlyLintPassObjects { lints: &mut passes[..] },
 345                 buffered,
 346                 pre_expansion,
 347             );
 348         }
 349     } else {
 350         for pass in &mut passes {
 351             buffered =
 352                 sess.prof.extra_verbose_generic_activity("run_lint", pass.name()).run(|| {
 353                     early_lint_crate(
 354                         sess,
 355                         lint_store,
 356                         krate,
 357                         EarlyLintPassObjects { lints: slice::from_mut(pass) },
 358                         buffered,
 359                         pre_expansion,
 360                     )
 361                 });
 362         }
 363     }
 364
 365     // All of the buffered lints should have been emitted at this point.
 366     // If not, that means that we somehow buffered a lint for a node id
 367     // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
 368     //
 369     // Rustdoc runs everybody-loops before the early lints and removes
 370     // function bodies, so it's totally possible for linted
 371     // node ids to not exist (e.g., macros defined within functions for the
 372     // unused_macro lint) anymore. So we only run this check
 373     // when we're not in rustdoc mode. (see issue #47639)
 374     if !sess.opts.actually_rustdoc {
 375         for (_id, lints) in buffered.map {
 376             for early_lint in lints {
 377                 sess.delay_span_bug(early_lint.span, "failed to process buffered lint here");
 378             }
 379         }
 380     }
 381 }