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::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;
  26 use rustc_span::Span;
  27
  28 use std::slice;
  29 use tracing::debug;
  30
  31 macro_rules! run_early_pass { ($cx:expr, $f:ident, $($args:expr),*) => ({
  32     $cx.pass.$f(&$cx.context, $($args),*);
  33 }) }
  34
  35 pub struct EarlyContextAndPass<'a, T: EarlyLintPass> {
  36     context: EarlyContext<'a>,
  37     pass: T,
  38 }
  39
  40 impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
  41     fn check_id(&mut self, id: ast::NodeId) {
  42         for early_lint in self.context.buffered.take(id) {
  43             let BufferedEarlyLint { span, msg, node_id: _, lint_id, diagnostic } = early_lint;
  44             self.context.lookup_with_diagnostics(
  45                 lint_id.lint,
  46                 Some(span),
  47                 |lint| {
  48                     lint.build(&msg).emit();
  49                 },
  50                 diagnostic,
  51             );
  52         }
  53     }
  54
  55     /// Merge the lints specified by any lint attributes into the
  56     /// current lint context, call the provided function, then reset the
  57     /// lints in effect to their previous state.
  58     fn with_lint_attrs<F>(&mut self, id: ast::NodeId, attrs: &'a [ast::Attribute], f: F)
  59     where
  60         F: FnOnce(&mut Self),
  61     {
  62         let is_crate_node = id == ast::CRATE_NODE_ID;
  63         let push = self.context.builder.push(attrs, is_crate_node, None);
  64
  65         self.check_id(id);
  66         debug!("early context: enter_attrs({:?})", attrs);
  67         run_early_pass!(self, enter_lint_attrs, attrs);
  68         f(self);
  69         debug!("early context: exit_attrs({:?})", attrs);
  70         run_early_pass!(self, exit_lint_attrs, attrs);
  71         self.context.builder.pop(push);
  72     }
  73 }
  74
  75 impl<'a, T: EarlyLintPass> ast_visit::Visitor<'a> for EarlyContextAndPass<'a, T> {
  76     fn visit_param(&mut self, param: &'a ast::Param) {
  77         self.with_lint_attrs(param.id, &param.attrs, |cx| {
  78             run_early_pass!(cx, check_param, param);
  79             ast_visit::walk_param(cx, param);
  80         });
  81     }
  82
  83     fn visit_item(&mut self, it: &'a ast::Item) {
  84         self.with_lint_attrs(it.id, &it.attrs, |cx| {
  85             run_early_pass!(cx, check_item, it);
  86             ast_visit::walk_item(cx, it);
  87             run_early_pass!(cx, check_item_post, it);
  88         })
  89     }
  90
  91     fn visit_foreign_item(&mut self, it: &'a ast::ForeignItem) {
  92         self.with_lint_attrs(it.id, &it.attrs, |cx| {
  93             run_early_pass!(cx, check_foreign_item, it);
  94             ast_visit::walk_foreign_item(cx, it);
  95             run_early_pass!(cx, check_foreign_item_post, it);
  96         })
  97     }
  98
  99     fn visit_pat(&mut self, p: &'a ast::Pat) {
 100         run_early_pass!(self, check_pat, p);
 101         self.check_id(p.id);
 102         ast_visit::walk_pat(self, p);
 103         run_early_pass!(self, check_pat_post, p);
 104     }
 105
 106     fn visit_anon_const(&mut self, c: &'a ast::AnonConst) {
 107         run_early_pass!(self, check_anon_const, c);
 108         self.check_id(c.id);
 109         ast_visit::walk_anon_const(self, c);
 110     }
 111
 112     fn visit_expr(&mut self, e: &'a ast::Expr) {
 113         self.with_lint_attrs(e.id, &e.attrs, |cx| {
 114             run_early_pass!(cx, check_expr, e);
 115             ast_visit::walk_expr(cx, e);
 116         })
 117     }
 118
 119     fn visit_expr_field(&mut self, f: &'a ast::ExprField) {
 120         self.with_lint_attrs(f.id, &f.attrs, |cx| {
 121             ast_visit::walk_expr_field(cx, f);
 122         })
 123     }
 124
 125     fn visit_stmt(&mut self, s: &'a ast::Stmt) {
 126         // Add the statement's lint attributes to our
 127         // current state when checking the statement itself.
 128         // This allows us to handle attributes like
 129         // `#[allow(unused_doc_comments)]`, which apply to
 130         // sibling attributes on the same target
 131         //
 132         // Note that statements get their attributes from
 133         // the AST struct that they wrap (e.g. an item)
 134         self.with_lint_attrs(s.id, s.attrs(), |cx| {
 135             run_early_pass!(cx, check_stmt, s);
 136             cx.check_id(s.id);
 137         });
 138         // The visitor for the AST struct wrapped
 139         // by the statement (e.g. `Item`) will call
 140         // `with_lint_attrs`, so do this walk
 141         // outside of the above `with_lint_attrs` call
 142         ast_visit::walk_stmt(self, s);
 143     }
 144
 145     fn visit_fn(&mut self, fk: ast_visit::FnKind<'a>, span: Span, id: ast::NodeId) {
 146         run_early_pass!(self, check_fn, fk, span, id);
 147         self.check_id(id);
 148         ast_visit::walk_fn(self, fk, span);
 149
 150         // Explicitly check for lints associated with 'closure_id', since
 151         // it does not have a corresponding AST node
 152         if let ast_visit::FnKind::Fn(_, _, sig, _, _, _) = fk {
 153             if let ast::Async::Yes { closure_id, .. } = sig.header.asyncness {
 154                 self.check_id(closure_id);
 155             }
 156         }
 157         run_early_pass!(self, check_fn_post, fk, span, id);
 158     }
 159
 160     fn visit_variant_data(&mut self, s: &'a ast::VariantData) {
 161         run_early_pass!(self, check_struct_def, s);
 162         if let Some(ctor_hir_id) = s.ctor_id() {
 163             self.check_id(ctor_hir_id);
 164         }
 165         ast_visit::walk_struct_def(self, s);
 166         run_early_pass!(self, check_struct_def_post, s);
 167     }
 168
 169     fn visit_field_def(&mut self, s: &'a ast::FieldDef) {
 170         self.with_lint_attrs(s.id, &s.attrs, |cx| {
 171             run_early_pass!(cx, check_field_def, s);
 172             ast_visit::walk_field_def(cx, s);
 173         })
 174     }
 175
 176     fn visit_variant(&mut self, v: &'a ast::Variant) {
 177         self.with_lint_attrs(v.id, &v.attrs, |cx| {
 178             run_early_pass!(cx, check_variant, v);
 179             ast_visit::walk_variant(cx, v);
 180             run_early_pass!(cx, check_variant_post, v);
 181         })
 182     }
 183
 184     fn visit_ty(&mut self, t: &'a ast::Ty) {
 185         run_early_pass!(self, check_ty, t);
 186         self.check_id(t.id);
 187         ast_visit::walk_ty(self, t);
 188     }
 189
 190     fn visit_ident(&mut self, ident: Ident) {
 191         run_early_pass!(self, check_ident, ident);
 192     }
 193
 194     fn visit_local(&mut self, l: &'a ast::Local) {
 195         self.with_lint_attrs(l.id, &l.attrs, |cx| {
 196             run_early_pass!(cx, check_local, l);
 197             ast_visit::walk_local(cx, l);
 198         })
 199     }
 200
 201     fn visit_block(&mut self, b: &'a ast::Block) {
 202         run_early_pass!(self, check_block, b);
 203         self.check_id(b.id);
 204         ast_visit::walk_block(self, b);
 205         run_early_pass!(self, check_block_post, b);
 206     }
 207
 208     fn visit_arm(&mut self, a: &'a ast::Arm) {
 209         self.with_lint_attrs(a.id, &a.attrs, |cx| {
 210             run_early_pass!(cx, check_arm, a);
 211             ast_visit::walk_arm(cx, a);
 212         })
 213     }
 214
 215     fn visit_expr_post(&mut self, e: &'a ast::Expr) {
 216         run_early_pass!(self, check_expr_post, e);
 217
 218         // Explicitly check for lints associated with 'closure_id', since
 219         // it does not have a corresponding AST node
 220         match e.kind {
 221             ast::ExprKind::Closure(_, ast::Async::Yes { closure_id, .. }, ..)
 222             | ast::ExprKind::Async(_, closure_id, ..) => self.check_id(closure_id),
 223             _ => {}
 224         }
 225     }
 226
 227     fn visit_generic_arg(&mut self, arg: &'a ast::GenericArg) {
 228         run_early_pass!(self, check_generic_arg, arg);
 229         ast_visit::walk_generic_arg(self, arg);
 230     }
 231
 232     fn visit_generic_param(&mut self, param: &'a ast::GenericParam) {
 233         run_early_pass!(self, check_generic_param, param);
 234         self.check_id(param.id);
 235         ast_visit::walk_generic_param(self, param);
 236     }
 237
 238     fn visit_generics(&mut self, g: &'a ast::Generics) {
 239         run_early_pass!(self, check_generics, g);
 240         ast_visit::walk_generics(self, g);
 241     }
 242
 243     fn visit_where_predicate(&mut self, p: &'a ast::WherePredicate) {
 244         run_early_pass!(self, check_where_predicate, p);
 245         ast_visit::walk_where_predicate(self, p);
 246     }
 247
 248     fn visit_poly_trait_ref(&mut self, t: &'a ast::PolyTraitRef, m: &'a ast::TraitBoundModifier) {
 249         run_early_pass!(self, check_poly_trait_ref, t, m);
 250         ast_visit::walk_poly_trait_ref(self, t, m);
 251     }
 252
 253     fn visit_assoc_item(&mut self, item: &'a ast::AssocItem, ctxt: ast_visit::AssocCtxt) {
 254         self.with_lint_attrs(item.id, &item.attrs, |cx| match ctxt {
 255             ast_visit::AssocCtxt::Trait => {
 256                 run_early_pass!(cx, check_trait_item, item);
 257                 ast_visit::walk_assoc_item(cx, item, ctxt);
 258                 run_early_pass!(cx, check_trait_item_post, item);
 259             }
 260             ast_visit::AssocCtxt::Impl => {
 261                 run_early_pass!(cx, check_impl_item, item);
 262                 ast_visit::walk_assoc_item(cx, item, ctxt);
 263                 run_early_pass!(cx, check_impl_item_post, item);
 264             }
 265         });
 266     }
 267
 268     fn visit_lifetime(&mut self, lt: &'a ast::Lifetime, _: ast_visit::LifetimeCtxt) {
 269         run_early_pass!(self, check_lifetime, lt);
 270         self.check_id(lt.id);
 271     }
 272
 273     fn visit_path(&mut self, p: &'a ast::Path, id: ast::NodeId) {
 274         run_early_pass!(self, check_path, p, id);
 275         self.check_id(id);
 276         ast_visit::walk_path(self, p);
 277     }
 278
 279     fn visit_path_segment(&mut self, path_span: Span, s: &'a ast::PathSegment) {
 280         self.check_id(s.id);
 281         ast_visit::walk_path_segment(self, path_span, s);
 282     }
 283
 284     fn visit_attribute(&mut self, attr: &'a ast::Attribute) {
 285         run_early_pass!(self, check_attribute, attr);
 286     }
 287
 288     fn visit_mac_def(&mut self, mac: &'a ast::MacroDef, id: ast::NodeId) {
 289         run_early_pass!(self, check_mac_def, mac, id);
 290         self.check_id(id);
 291     }
 292
 293     fn visit_mac_call(&mut self, mac: &'a ast::MacCall) {
 294         run_early_pass!(self, check_mac, mac);
 295         ast_visit::walk_mac(self, mac);
 296     }
 297 }
 298
 299 struct EarlyLintPassObjects<'a> {
 300     lints: &'a mut [EarlyLintPassObject],
 301 }
 302
 303 #[allow(rustc::lint_pass_impl_without_macro)]
 304 impl LintPass for EarlyLintPassObjects<'_> {
 305     fn name(&self) -> &'static str {
 306         panic!()
 307     }
 308 }
 309
 310 macro_rules! expand_early_lint_pass_impl_methods {
 311     ([$($(#[$attr:meta])* fn $name:ident($($param:ident: $arg:ty),*);)*]) => (
 312         $(fn $name(&mut self, context: &EarlyContext<'_>, $($param: $arg),*) {
 313             for obj in self.lints.iter_mut() {
 314                 obj.$name(context, $($param),*);
 315             }
 316         })*
 317     )
 318 }
 319
 320 macro_rules! early_lint_pass_impl {
 321     ([], [$($methods:tt)*]) => (
 322         impl EarlyLintPass for EarlyLintPassObjects<'_> {
 323             expand_early_lint_pass_impl_methods!([$($methods)*]);
 324         }
 325     )
 326 }
 327
 328 crate::early_lint_methods!(early_lint_pass_impl, []);
 329
 330 /// Early lints work on different nodes - either on the crate root, or on freshly loaded modules.
 331 /// This trait generalizes over those nodes.
 332 pub trait EarlyCheckNode<'a>: Copy {
 333     fn id(self) -> ast::NodeId;
 334     fn attrs<'b>(self) -> &'b [ast::Attribute]
 335     where
 336         'a: 'b;
 337     fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
 338     where
 339         'a: 'b;
 340 }
 341
 342 impl<'a> EarlyCheckNode<'a> for &'a ast::Crate {
 343     fn id(self) -> ast::NodeId {
 344         ast::CRATE_NODE_ID
 345     }
 346     fn attrs<'b>(self) -> &'b [ast::Attribute]
 347     where
 348         'a: 'b,
 349     {
 350         &self.attrs
 351     }
 352     fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
 353     where
 354         'a: 'b,
 355     {
 356         run_early_pass!(cx, check_crate, self);
 357         ast_visit::walk_crate(cx, self);
 358         run_early_pass!(cx, check_crate_post, self);
 359     }
 360 }
 361
 362 impl<'a> EarlyCheckNode<'a> for (ast::NodeId, &'a [ast::Attribute], &'a [P<ast::Item>]) {
 363     fn id(self) -> ast::NodeId {
 364         self.0
 365     }
 366     fn attrs<'b>(self) -> &'b [ast::Attribute]
 367     where
 368         'a: 'b,
 369     {
 370         self.1
 371     }
 372     fn check<'b>(self, cx: &mut EarlyContextAndPass<'b, impl EarlyLintPass>)
 373     where
 374         'a: 'b,
 375     {
 376         walk_list!(cx, visit_attribute, self.1);
 377         walk_list!(cx, visit_item, self.2);
 378     }
 379 }
 380
 381 fn early_lint_node<'a>(
 382     sess: &Session,
 383     warn_about_weird_lints: bool,
 384     lint_store: &LintStore,
 385     registered_tools: &RegisteredTools,
 386     buffered: LintBuffer,
 387     pass: impl EarlyLintPass,
 388     check_node: impl EarlyCheckNode<'a>,
 389 ) -> LintBuffer {
 390     let mut cx = EarlyContextAndPass {
 391         context: EarlyContext::new(
 392             sess,
 393             warn_about_weird_lints,
 394             lint_store,
 395             registered_tools,
 396             buffered,
 397         ),
 398         pass,
 399     };
 400
 401     cx.with_lint_attrs(check_node.id(), check_node.attrs(), |cx| check_node.check(cx));
 402     cx.context.buffered
 403 }
 404
 405 pub fn check_ast_node<'a>(
 406     sess: &Session,
 407     pre_expansion: bool,
 408     lint_store: &LintStore,
 409     registered_tools: &RegisteredTools,
 410     lint_buffer: Option<LintBuffer>,
 411     builtin_lints: impl EarlyLintPass,
 412     check_node: impl EarlyCheckNode<'a>,
 413 ) {
 414     let passes =
 415         if pre_expansion { &lint_store.pre_expansion_passes } else { &lint_store.early_passes };
 416     let mut passes: Vec<_> = passes.iter().map(|p| (p)()).collect();
 417     let mut buffered = lint_buffer.unwrap_or_default();
 418
 419     if sess.opts.debugging_opts.no_interleave_lints {
 420         for (i, pass) in passes.iter_mut().enumerate() {
 421             buffered =
 422                 sess.prof.extra_verbose_generic_activity("run_lint", pass.name()).run(|| {
 423                     early_lint_node(
 424                         sess,
 425                         !pre_expansion && i == 0,
 426                         lint_store,
 427                         registered_tools,
 428                         buffered,
 429                         EarlyLintPassObjects { lints: slice::from_mut(pass) },
 430                         check_node,
 431                     )
 432                 });
 433         }
 434     } else {
 435         buffered = early_lint_node(
 436             sess,
 437             !pre_expansion,
 438             lint_store,
 439             registered_tools,
 440             buffered,
 441             builtin_lints,
 442             check_node,
 443         );
 444
 445         if !passes.is_empty() {
 446             buffered = early_lint_node(
 447                 sess,
 448                 false,
 449                 lint_store,
 450                 registered_tools,
 451                 buffered,
 452                 EarlyLintPassObjects { lints: &mut passes[..] },
 453                 check_node,
 454             );
 455         }
 456     }
 457
 458     // All of the buffered lints should have been emitted at this point.
 459     // If not, that means that we somehow buffered a lint for a node id
 460     // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
 461     for (id, lints) in buffered.map {
 462         for early_lint in lints {
 463             sess.delay_span_bug(
 464                 early_lint.span,
 465                 &format!(
 466                     "failed to process buffered lint here (dummy = {})",
 467                     id == ast::DUMMY_NODE_ID
 468                 ),
 469             );
 470         }
 471     }
 472 }