src/librustc_lint/late.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::{passes::LateLintPassObject, LateContext, LateLintPass, LintStore};
  18 use rustc_ast::ast;
  19 use rustc_ast::walk_list;
  20 use rustc_data_structures::sync::{join, par_iter, ParallelIterator};
  21 use rustc_hir as hir;
  22 use rustc_hir::def_id::{LocalDefId, LOCAL_CRATE};
  23 use rustc_hir::intravisit as hir_visit;
  24 use rustc_hir::intravisit::Visitor;
  25 use rustc_middle::hir::map::Map;
  26 use rustc_middle::ty::{self, TyCtxt};
  27 use rustc_session::lint::LintPass;
  28 use rustc_span::symbol::Symbol;
  29 use rustc_span::Span;
  30
  31 use log::debug;
  32 use std::any::Any;
  33 use std::cell::Cell;
  34 use std::slice;
  35
  36 /// Extract the `LintStore` from the query context.
  37 /// This function exists because we've erased `LintStore` as `dyn Any` in the context.
  38 crate fn unerased_lint_store(tcx: TyCtxt<'_>) -> &LintStore {
  39     let store: &dyn Any = &*tcx.lint_store;
  40     store.downcast_ref().unwrap()
  41 }
  42
  43 macro_rules! lint_callback { ($cx:expr, $f:ident, $($args:expr),*) => ({
  44     $cx.pass.$f(&$cx.context, $($args),*);
  45 }) }
  46
  47 struct LateContextAndPass<'tcx, T: LateLintPass<'tcx>> {
  48     context: LateContext<'tcx>,
  49     pass: T,
  50 }
  51
  52 impl<'tcx, T: LateLintPass<'tcx>> LateContextAndPass<'tcx, T> {
  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: hir::HirId, attrs: &'tcx [ast::Attribute], f: F)
  57     where
  58         F: FnOnce(&mut Self),
  59     {
  60         let prev = self.context.last_node_with_lint_attrs;
  61         self.context.last_node_with_lint_attrs = id;
  62         self.enter_attrs(attrs);
  63         f(self);
  64         self.exit_attrs(attrs);
  65         self.context.last_node_with_lint_attrs = prev;
  66     }
  67
  68     fn with_param_env<F>(&mut self, id: hir::HirId, f: F)
  69     where
  70         F: FnOnce(&mut Self),
  71     {
  72         let old_param_env = self.context.param_env;
  73         self.context.param_env =
  74             self.context.tcx.param_env(self.context.tcx.hir().local_def_id(id));
  75         f(self);
  76         self.context.param_env = old_param_env;
  77     }
  78
  79     fn process_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
  80         lint_callback!(self, check_mod, m, s, n);
  81         hir_visit::walk_mod(self, m, n);
  82         lint_callback!(self, check_mod_post, m, s, n);
  83     }
  84
  85     fn enter_attrs(&mut self, attrs: &'tcx [ast::Attribute]) {
  86         debug!("late context: enter_attrs({:?})", attrs);
  87         lint_callback!(self, enter_lint_attrs, attrs);
  88     }
  89
  90     fn exit_attrs(&mut self, attrs: &'tcx [ast::Attribute]) {
  91         debug!("late context: exit_attrs({:?})", attrs);
  92         lint_callback!(self, exit_lint_attrs, attrs);
  93     }
  94 }
  95
  96 impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPass<'tcx, T> {
  97     type Map = Map<'tcx>;
  98
  99     /// Because lints are scoped lexically, we want to walk nested
 100     /// items in the context of the outer item, so enable
 101     /// deep-walking.
 102     fn nested_visit_map(&mut self) -> hir_visit::NestedVisitorMap<Self::Map> {
 103         hir_visit::NestedVisitorMap::All(self.context.tcx.hir())
 104     }
 105
 106     fn visit_nested_body(&mut self, body_id: hir::BodyId) {
 107         let old_enclosing_body = self.context.enclosing_body.replace(body_id);
 108         let old_cached_typeck_tables = self.context.cached_typeck_tables.get();
 109
 110         // HACK(eddyb) avoid trashing `cached_typeck_tables` when we're
 111         // nested in `visit_fn`, which may have already resulted in them
 112         // being queried.
 113         if old_enclosing_body != Some(body_id) {
 114             self.context.cached_typeck_tables.set(None);
 115         }
 116
 117         let body = self.context.tcx.hir().body(body_id);
 118         self.visit_body(body);
 119         self.context.enclosing_body = old_enclosing_body;
 120
 121         // See HACK comment above.
 122         if old_enclosing_body != Some(body_id) {
 123             self.context.cached_typeck_tables.set(old_cached_typeck_tables);
 124         }
 125     }
 126
 127     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
 128         self.with_lint_attrs(param.hir_id, &param.attrs, |cx| {
 129             lint_callback!(cx, check_param, param);
 130             hir_visit::walk_param(cx, param);
 131         });
 132     }
 133
 134     fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
 135         lint_callback!(self, check_body, body);
 136         hir_visit::walk_body(self, body);
 137         lint_callback!(self, check_body_post, body);
 138     }
 139
 140     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
 141         let generics = self.context.generics.take();
 142         self.context.generics = it.kind.generics();
 143         self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
 144             cx.with_param_env(it.hir_id, |cx| {
 145                 lint_callback!(cx, check_item, it);
 146                 hir_visit::walk_item(cx, it);
 147                 lint_callback!(cx, check_item_post, it);
 148             });
 149         });
 150         self.context.generics = generics;
 151     }
 152
 153     fn visit_foreign_item(&mut self, it: &'tcx hir::ForeignItem<'tcx>) {
 154         self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
 155             cx.with_param_env(it.hir_id, |cx| {
 156                 lint_callback!(cx, check_foreign_item, it);
 157                 hir_visit::walk_foreign_item(cx, it);
 158                 lint_callback!(cx, check_foreign_item_post, it);
 159             });
 160         })
 161     }
 162
 163     fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
 164         lint_callback!(self, check_pat, p);
 165         hir_visit::walk_pat(self, p);
 166     }
 167
 168     fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
 169         self.with_lint_attrs(e.hir_id, &e.attrs, |cx| {
 170             lint_callback!(cx, check_expr, e);
 171             hir_visit::walk_expr(cx, e);
 172             lint_callback!(cx, check_expr_post, e);
 173         })
 174     }
 175
 176     fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
 177         // statement attributes are actually just attributes on one of
 178         // - item
 179         // - local
 180         // - expression
 181         // so we keep track of lint levels there
 182         lint_callback!(self, check_stmt, s);
 183         hir_visit::walk_stmt(self, s);
 184     }
 185
 186     fn visit_fn(
 187         &mut self,
 188         fk: hir_visit::FnKind<'tcx>,
 189         decl: &'tcx hir::FnDecl<'tcx>,
 190         body_id: hir::BodyId,
 191         span: Span,
 192         id: hir::HirId,
 193     ) {
 194         // Wrap in tables here, not just in visit_nested_body,
 195         // in order for `check_fn` to be able to use them.
 196         let old_enclosing_body = self.context.enclosing_body.replace(body_id);
 197         let old_cached_typeck_tables = self.context.cached_typeck_tables.take();
 198         let body = self.context.tcx.hir().body(body_id);
 199         lint_callback!(self, check_fn, fk, decl, body, span, id);
 200         hir_visit::walk_fn(self, fk, decl, body_id, span, id);
 201         lint_callback!(self, check_fn_post, fk, decl, body, span, id);
 202         self.context.enclosing_body = old_enclosing_body;
 203         self.context.cached_typeck_tables.set(old_cached_typeck_tables);
 204     }
 205
 206     fn visit_variant_data(
 207         &mut self,
 208         s: &'tcx hir::VariantData<'tcx>,
 209         _: Symbol,
 210         _: &'tcx hir::Generics<'tcx>,
 211         _: hir::HirId,
 212         _: Span,
 213     ) {
 214         lint_callback!(self, check_struct_def, s);
 215         hir_visit::walk_struct_def(self, s);
 216         lint_callback!(self, check_struct_def_post, s);
 217     }
 218
 219     fn visit_struct_field(&mut self, s: &'tcx hir::StructField<'tcx>) {
 220         self.with_lint_attrs(s.hir_id, &s.attrs, |cx| {
 221             lint_callback!(cx, check_struct_field, s);
 222             hir_visit::walk_struct_field(cx, s);
 223         })
 224     }
 225
 226     fn visit_variant(
 227         &mut self,
 228         v: &'tcx hir::Variant<'tcx>,
 229         g: &'tcx hir::Generics<'tcx>,
 230         item_id: hir::HirId,
 231     ) {
 232         self.with_lint_attrs(v.id, &v.attrs, |cx| {
 233             lint_callback!(cx, check_variant, v);
 234             hir_visit::walk_variant(cx, v, g, item_id);
 235             lint_callback!(cx, check_variant_post, v);
 236         })
 237     }
 238
 239     fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
 240         lint_callback!(self, check_ty, t);
 241         hir_visit::walk_ty(self, t);
 242     }
 243
 244     fn visit_name(&mut self, sp: Span, name: Symbol) {
 245         lint_callback!(self, check_name, sp, name);
 246     }
 247
 248     fn visit_mod(&mut self, m: &'tcx hir::Mod<'tcx>, s: Span, n: hir::HirId) {
 249         if !self.context.only_module {
 250             self.process_mod(m, s, n);
 251         }
 252     }
 253
 254     fn visit_local(&mut self, l: &'tcx hir::Local<'tcx>) {
 255         self.with_lint_attrs(l.hir_id, &l.attrs, |cx| {
 256             lint_callback!(cx, check_local, l);
 257             hir_visit::walk_local(cx, l);
 258         })
 259     }
 260
 261     fn visit_block(&mut self, b: &'tcx hir::Block<'tcx>) {
 262         lint_callback!(self, check_block, b);
 263         hir_visit::walk_block(self, b);
 264         lint_callback!(self, check_block_post, b);
 265     }
 266
 267     fn visit_arm(&mut self, a: &'tcx hir::Arm<'tcx>) {
 268         lint_callback!(self, check_arm, a);
 269         hir_visit::walk_arm(self, a);
 270     }
 271
 272     fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
 273         lint_callback!(self, check_generic_param, p);
 274         hir_visit::walk_generic_param(self, p);
 275     }
 276
 277     fn visit_generics(&mut self, g: &'tcx hir::Generics<'tcx>) {
 278         lint_callback!(self, check_generics, g);
 279         hir_visit::walk_generics(self, g);
 280     }
 281
 282     fn visit_where_predicate(&mut self, p: &'tcx hir::WherePredicate<'tcx>) {
 283         lint_callback!(self, check_where_predicate, p);
 284         hir_visit::walk_where_predicate(self, p);
 285     }
 286
 287     fn visit_poly_trait_ref(
 288         &mut self,
 289         t: &'tcx hir::PolyTraitRef<'tcx>,
 290         m: hir::TraitBoundModifier,
 291     ) {
 292         lint_callback!(self, check_poly_trait_ref, t, m);
 293         hir_visit::walk_poly_trait_ref(self, t, m);
 294     }
 295
 296     fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
 297         let generics = self.context.generics.take();
 298         self.context.generics = Some(&trait_item.generics);
 299         self.with_lint_attrs(trait_item.hir_id, &trait_item.attrs, |cx| {
 300             cx.with_param_env(trait_item.hir_id, |cx| {
 301                 lint_callback!(cx, check_trait_item, trait_item);
 302                 hir_visit::walk_trait_item(cx, trait_item);
 303                 lint_callback!(cx, check_trait_item_post, trait_item);
 304             });
 305         });
 306         self.context.generics = generics;
 307     }
 308
 309     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
 310         let generics = self.context.generics.take();
 311         self.context.generics = Some(&impl_item.generics);
 312         self.with_lint_attrs(impl_item.hir_id, &impl_item.attrs, |cx| {
 313             cx.with_param_env(impl_item.hir_id, |cx| {
 314                 lint_callback!(cx, check_impl_item, impl_item);
 315                 hir_visit::walk_impl_item(cx, impl_item);
 316                 lint_callback!(cx, check_impl_item_post, impl_item);
 317             });
 318         });
 319         self.context.generics = generics;
 320     }
 321
 322     fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) {
 323         lint_callback!(self, check_lifetime, lt);
 324         hir_visit::walk_lifetime(self, lt);
 325     }
 326
 327     fn visit_path(&mut self, p: &'tcx hir::Path<'tcx>, id: hir::HirId) {
 328         lint_callback!(self, check_path, p, id);
 329         hir_visit::walk_path(self, p);
 330     }
 331
 332     fn visit_attribute(&mut self, attr: &'tcx ast::Attribute) {
 333         lint_callback!(self, check_attribute, attr);
 334     }
 335 }
 336
 337 struct LateLintPassObjects<'a> {
 338     lints: &'a mut [LateLintPassObject],
 339 }
 340
 341 #[allow(rustc::lint_pass_impl_without_macro)]
 342 impl LintPass for LateLintPassObjects<'_> {
 343     fn name(&self) -> &'static str {
 344         panic!()
 345     }
 346 }
 347
 348 macro_rules! expand_late_lint_pass_impl_methods {
 349     ([$hir:tt], [$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 350         $(fn $name(&mut self, context: &LateContext<$hir>, $($param: $arg),*) {
 351             for obj in self.lints.iter_mut() {
 352                 obj.$name(context, $($param),*);
 353             }
 354         })*
 355     )
 356 }
 357
 358 macro_rules! late_lint_pass_impl {
 359     ([], [$hir:tt], $methods:tt) => {
 360         impl<$hir> LateLintPass<$hir> for LateLintPassObjects<'_> {
 361             expand_late_lint_pass_impl_methods!([$hir], $methods);
 362         }
 363     };
 364 }
 365
 366 crate::late_lint_methods!(late_lint_pass_impl, [], ['tcx]);
 367
 368 fn late_lint_mod_pass<'tcx, T: LateLintPass<'tcx>>(
 369     tcx: TyCtxt<'tcx>,
 370     module_def_id: LocalDefId,
 371     pass: T,
 372 ) {
 373     let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
 374
 375     let context = LateContext {
 376         tcx,
 377         enclosing_body: None,
 378         cached_typeck_tables: Cell::new(None),
 379         param_env: ty::ParamEnv::empty(),
 380         access_levels,
 381         lint_store: unerased_lint_store(tcx),
 382         last_node_with_lint_attrs: tcx.hir().as_local_hir_id(module_def_id),
 383         generics: None,
 384         only_module: true,
 385     };
 386
 387     let mut cx = LateContextAndPass { context, pass };
 388
 389     let (module, span, hir_id) = tcx.hir().get_module(module_def_id);
 390     cx.process_mod(module, span, hir_id);
 391
 392     // Visit the crate attributes
 393     if hir_id == hir::CRATE_HIR_ID {
 394         walk_list!(cx, visit_attribute, tcx.hir().attrs(hir::CRATE_HIR_ID));
 395     }
 396 }
 397
 398 pub fn late_lint_mod<'tcx, T: LateLintPass<'tcx>>(
 399     tcx: TyCtxt<'tcx>,
 400     module_def_id: LocalDefId,
 401     builtin_lints: T,
 402 ) {
 403     if tcx.sess.opts.debugging_opts.no_interleave_lints {
 404         // These passes runs in late_lint_crate with -Z no_interleave_lints
 405         return;
 406     }
 407
 408     late_lint_mod_pass(tcx, module_def_id, builtin_lints);
 409
 410     let mut passes: Vec<_> =
 411         unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
 412
 413     if !passes.is_empty() {
 414         late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
 415     }
 416 }
 417
 418 fn late_lint_pass_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, pass: T) {
 419     let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
 420
 421     let krate = tcx.hir().krate();
 422
 423     let context = LateContext {
 424         tcx,
 425         enclosing_body: None,
 426         cached_typeck_tables: Cell::new(None),
 427         param_env: ty::ParamEnv::empty(),
 428         access_levels,
 429         lint_store: unerased_lint_store(tcx),
 430         last_node_with_lint_attrs: hir::CRATE_HIR_ID,
 431         generics: None,
 432         only_module: false,
 433     };
 434
 435     let mut cx = LateContextAndPass { context, pass };
 436
 437     // Visit the whole crate.
 438     cx.with_lint_attrs(hir::CRATE_HIR_ID, &krate.item.attrs, |cx| {
 439         // since the root module isn't visited as an item (because it isn't an
 440         // item), warn for it here.
 441         lint_callback!(cx, check_crate, krate);
 442
 443         hir_visit::walk_crate(cx, krate);
 444
 445         lint_callback!(cx, check_crate_post, krate);
 446     })
 447 }
 448
 449 fn late_lint_crate<'tcx, T: LateLintPass<'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
 450     let mut passes = unerased_lint_store(tcx).late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
 451
 452     if !tcx.sess.opts.debugging_opts.no_interleave_lints {
 453         if !passes.is_empty() {
 454             late_lint_pass_crate(tcx, LateLintPassObjects { lints: &mut passes[..] });
 455         }
 456
 457         late_lint_pass_crate(tcx, builtin_lints);
 458     } else {
 459         for pass in &mut passes {
 460             tcx.sess.prof.extra_verbose_generic_activity("run_late_lint", pass.name()).run(|| {
 461                 late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
 462             });
 463         }
 464
 465         let mut passes: Vec<_> =
 466             unerased_lint_store(tcx).late_module_passes.iter().map(|pass| (pass)()).collect();
 467
 468         for pass in &mut passes {
 469             tcx.sess.prof.extra_verbose_generic_activity("run_late_module_lint", pass.name()).run(
 470                 || {
 471                     late_lint_pass_crate(tcx, LateLintPassObjects { lints: slice::from_mut(pass) });
 472                 },
 473             );
 474         }
 475     }
 476 }
 477
 478 /// Performs lint checking on a crate.
 479 pub fn check_crate<'tcx, T: LateLintPass<'tcx>>(
 480     tcx: TyCtxt<'tcx>,
 481     builtin_lints: impl FnOnce() -> T + Send,
 482 ) {
 483     join(
 484         || {
 485             tcx.sess.time("crate_lints", || {
 486                 // Run whole crate non-incremental lints
 487                 late_lint_crate(tcx, builtin_lints());
 488             });
 489         },
 490         || {
 491             tcx.sess.time("module_lints", || {
 492                 // Run per-module lints
 493                 par_iter(&tcx.hir().krate().modules).for_each(|(&module, _)| {
 494                     tcx.ensure().lint_mod(tcx.hir().local_def_id(module));
 495                 });
 496             });
 497         },
 498     );
 499 }