compiler/rustc_passes/src/check_attr.rs

   1 //! This module implements some validity checks for attributes.
   2 //! In particular it verifies that `#[inline]` and `#[repr]` attributes are
   3 //! attached to items that actually support them and if there are
   4 //! conflicts between multiple such attributes attached to the same
   5 //! item.
   6
   7 use crate::errors;
   8 use rustc_ast::{ast, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
   9 use rustc_data_structures::fx::FxHashMap;
  10 use rustc_errors::{fluent, struct_span_err, Applicability, MultiSpan};
  11 use rustc_expand::base::resolve_path;
  12 use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
  13 use rustc_hir as hir;
  14 use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID};
  15 use rustc_hir::intravisit::{self, Visitor};
  16 use rustc_hir::{self, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID};
  17 use rustc_hir::{MethodKind, Target};
  18 use rustc_middle::hir::nested_filter;
  19 use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
  20 use rustc_middle::ty::query::Providers;
  21 use rustc_middle::ty::TyCtxt;
  22 use rustc_session::lint::builtin::{
  23     CONFLICTING_REPR_HINTS, INVALID_DOC_ATTRIBUTES, UNUSED_ATTRIBUTES,
  24 };
  25 use rustc_session::parse::feature_err;
  26 use rustc_span::symbol::{kw, sym, Symbol};
  27 use rustc_span::{Span, DUMMY_SP};
  28 use rustc_target::spec::abi::Abi;
  29 use std::collections::hash_map::Entry;
  30
  31 pub(crate) fn target_from_impl_item<'tcx>(
  32     tcx: TyCtxt<'tcx>,
  33     impl_item: &hir::ImplItem<'_>,
  34 ) -> Target {
  35     match impl_item.kind {
  36         hir::ImplItemKind::Const(..) => Target::AssocConst,
  37         hir::ImplItemKind::Fn(..) => {
  38             let parent_hir_id = tcx.hir().get_parent_item(impl_item.hir_id());
  39             let containing_item = tcx.hir().expect_item(parent_hir_id);
  40             let containing_impl_is_for_trait = match &containing_item.kind {
  41                 hir::ItemKind::Impl(impl_) => impl_.of_trait.is_some(),
  42                 _ => bug!("parent of an ImplItem must be an Impl"),
  43             };
  44             if containing_impl_is_for_trait {
  45                 Target::Method(MethodKind::Trait { body: true })
  46             } else {
  47                 Target::Method(MethodKind::Inherent)
  48             }
  49         }
  50         hir::ImplItemKind::TyAlias(..) => Target::AssocTy,
  51     }
  52 }
  53
  54 #[derive(Clone, Copy)]
  55 enum ItemLike<'tcx> {
  56     Item(&'tcx Item<'tcx>),
  57     ForeignItem,
  58 }
  59
  60 struct CheckAttrVisitor<'tcx> {
  61     tcx: TyCtxt<'tcx>,
  62 }
  63
  64 impl CheckAttrVisitor<'_> {
  65     /// Checks any attribute.
  66     fn check_attributes(
  67         &self,
  68         hir_id: HirId,
  69         span: Span,
  70         target: Target,
  71         item: Option<ItemLike<'_>>,
  72     ) {
  73         let mut doc_aliases = FxHashMap::default();
  74         let mut is_valid = true;
  75         let mut specified_inline = None;
  76         let mut seen = FxHashMap::default();
  77         let attrs = self.tcx.hir().attrs(hir_id);
  78         for attr in attrs {
  79             let attr_is_valid = match attr.name_or_empty() {
  80                 sym::inline => self.check_inline(hir_id, attr, span, target),
  81                 sym::no_coverage => self.check_no_coverage(hir_id, attr, span, target),
  82                 sym::non_exhaustive => self.check_non_exhaustive(hir_id, attr, span, target),
  83                 sym::marker => self.check_marker(hir_id, attr, span, target),
  84                 sym::rustc_must_implement_one_of => {
  85                     self.check_rustc_must_implement_one_of(attr, span, target)
  86                 }
  87                 sym::target_feature => self.check_target_feature(hir_id, attr, span, target),
  88                 sym::thread_local => self.check_thread_local(attr, span, target),
  89                 sym::track_caller => {
  90                     self.check_track_caller(hir_id, attr.span, attrs, span, target)
  91                 }
  92                 sym::doc => self.check_doc_attrs(
  93                     attr,
  94                     hir_id,
  95                     target,
  96                     &mut specified_inline,
  97                     &mut doc_aliases,
  98                 ),
  99                 sym::no_link => self.check_no_link(hir_id, &attr, span, target),
 100                 sym::export_name => self.check_export_name(hir_id, &attr, span, target),
 101                 sym::rustc_layout_scalar_valid_range_start
 102                 | sym::rustc_layout_scalar_valid_range_end => {
 103                     self.check_rustc_layout_scalar_valid_range(&attr, span, target)
 104                 }
 105                 sym::allow_internal_unstable => {
 106                     self.check_allow_internal_unstable(hir_id, &attr, span, target, &attrs)
 107                 }
 108                 sym::debugger_visualizer => self.check_debugger_visualizer(&attr, target),
 109                 sym::rustc_allow_const_fn_unstable => {
 110                     self.check_rustc_allow_const_fn_unstable(hir_id, &attr, span, target)
 111                 }
 112                 sym::rustc_std_internal_symbol => {
 113                     self.check_rustc_std_internal_symbol(&attr, span, target)
 114                 }
 115                 sym::naked => self.check_naked(hir_id, attr, span, target),
 116                 sym::rustc_legacy_const_generics => {
 117                     self.check_rustc_legacy_const_generics(&attr, span, target, item)
 118                 }
 119                 sym::rustc_lint_query_instability => {
 120                     self.check_rustc_lint_query_instability(&attr, span, target)
 121                 }
 122                 sym::rustc_lint_diagnostics => {
 123                     self.check_rustc_lint_diagnostics(&attr, span, target)
 124                 }
 125                 sym::rustc_lint_opt_ty => self.check_rustc_lint_opt_ty(&attr, span, target),
 126                 sym::rustc_lint_opt_deny_field_access => {
 127                     self.check_rustc_lint_opt_deny_field_access(&attr, span, target)
 128                 }
 129                 sym::rustc_clean
 130                 | sym::rustc_dirty
 131                 | sym::rustc_if_this_changed
 132                 | sym::rustc_then_this_would_need => self.check_rustc_dirty_clean(&attr),
 133                 sym::cmse_nonsecure_entry => self.check_cmse_nonsecure_entry(attr, span, target),
 134                 sym::const_trait => self.check_const_trait(attr, span, target),
 135                 sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target),
 136                 sym::must_use => self.check_must_use(hir_id, &attr, span, target),
 137                 sym::rustc_pass_by_value => self.check_pass_by_value(&attr, span, target),
 138                 sym::rustc_allow_incoherent_impl => {
 139                     self.check_allow_incoherent_impl(&attr, span, target)
 140                 }
 141                 sym::rustc_has_incoherent_inherent_impls => {
 142                     self.check_has_incoherent_inherent_impls(&attr, span, target)
 143                 }
 144                 sym::rustc_const_unstable
 145                 | sym::rustc_const_stable
 146                 | sym::unstable
 147                 | sym::stable
 148                 | sym::rustc_allowed_through_unstable_modules
 149                 | sym::rustc_promotable => self.check_stability_promotable(&attr, span, target),
 150                 sym::link_ordinal => self.check_link_ordinal(&attr, span, target),
 151                 _ => true,
 152             };
 153             is_valid &= attr_is_valid;
 154
 155             // lint-only checks
 156             match attr.name_or_empty() {
 157                 sym::cold => self.check_cold(hir_id, attr, span, target),
 158                 sym::link => self.check_link(hir_id, attr, span, target),
 159                 sym::link_name => self.check_link_name(hir_id, attr, span, target),
 160                 sym::link_section => self.check_link_section(hir_id, attr, span, target),
 161                 sym::no_mangle => self.check_no_mangle(hir_id, attr, span, target),
 162                 sym::deprecated => self.check_deprecated(hir_id, attr, span, target),
 163                 sym::macro_use | sym::macro_escape => self.check_macro_use(hir_id, attr, target),
 164                 sym::path => self.check_generic_attr(hir_id, attr, target, &[Target::Mod]),
 165                 sym::plugin_registrar => self.check_plugin_registrar(hir_id, attr, target),
 166                 sym::macro_export => self.check_macro_export(hir_id, attr, target),
 167                 sym::ignore | sym::should_panic | sym::proc_macro_derive => {
 168                     self.check_generic_attr(hir_id, attr, target, &[Target::Fn])
 169                 }
 170                 sym::automatically_derived => {
 171                     self.check_generic_attr(hir_id, attr, target, &[Target::Impl])
 172                 }
 173                 sym::no_implicit_prelude => {
 174                     self.check_generic_attr(hir_id, attr, target, &[Target::Mod])
 175                 }
 176                 sym::rustc_object_lifetime_default => self.check_object_lifetime_default(hir_id),
 177                 _ => {}
 178             }
 179
 180             let builtin = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
 181
 182             if hir_id != CRATE_HIR_ID {
 183                 if let Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) =
 184                     attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name))
 185                 {
 186                     match attr.style {
 187                         ast::AttrStyle::Outer => self.tcx.emit_spanned_lint(
 188                             UNUSED_ATTRIBUTES,
 189                             hir_id,
 190                             attr.span,
 191                             errors::OuterCrateLevelAttr,
 192                         ),
 193                         ast::AttrStyle::Inner => self.tcx.emit_spanned_lint(
 194                             UNUSED_ATTRIBUTES,
 195                             hir_id,
 196                             attr.span,
 197                             errors::InnerCrateLevelAttr,
 198                         ),
 199                     }
 200                 }
 201             }
 202
 203             if let Some(BuiltinAttribute { duplicates, .. }) = builtin {
 204                 check_duplicates(self.tcx, attr, hir_id, *duplicates, &mut seen);
 205             }
 206
 207             self.check_unused_attribute(hir_id, attr)
 208         }
 209
 210         if !is_valid {
 211             return;
 212         }
 213
 214         // FIXME(@lcnr): this doesn't belong here.
 215         if matches!(
 216             target,
 217             Target::Closure
 218                 | Target::Fn
 219                 | Target::Method(_)
 220                 | Target::ForeignFn
 221                 | Target::ForeignStatic
 222         ) {
 223             self.tcx.ensure().codegen_fn_attrs(self.tcx.hir().local_def_id(hir_id));
 224         }
 225
 226         self.check_repr(attrs, span, target, item, hir_id);
 227         self.check_used(attrs, target);
 228     }
 229
 230     fn inline_attr_str_error_with_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
 231         self.tcx.emit_spanned_lint(
 232             UNUSED_ATTRIBUTES,
 233             hir_id,
 234             attr.span,
 235             errors::IgnoredAttrWithMacro { sym },
 236         );
 237     }
 238
 239     fn inline_attr_str_error_without_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
 240         self.tcx.emit_spanned_lint(
 241             UNUSED_ATTRIBUTES,
 242             hir_id,
 243             attr.span,
 244             errors::IgnoredAttr { sym },
 245         );
 246     }
 247
 248     /// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid.
 249     fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
 250         match target {
 251             Target::Fn
 252             | Target::Closure
 253             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 254             Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
 255                 self.tcx.emit_spanned_lint(
 256                     UNUSED_ATTRIBUTES,
 257                     hir_id,
 258                     attr.span,
 259                     errors::IgnoredInlineAttrFnProto,
 260                 );
 261                 true
 262             }
 263             // FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with
 264             // just a lint, because we previously erroneously allowed it and some crates used it
 265             // accidentally, to to be compatible with crates depending on them, we can't throw an
 266             // error here.
 267             Target::AssocConst => {
 268                 self.tcx.emit_spanned_lint(
 269                     UNUSED_ATTRIBUTES,
 270                     hir_id,
 271                     attr.span,
 272                     errors::IgnoredInlineAttrConstants,
 273                 );
 274                 true
 275             }
 276             // FIXME(#80564): Same for fields, arms, and macro defs
 277             Target::Field | Target::Arm | Target::MacroDef => {
 278                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "inline");
 279                 true
 280             }
 281             _ => {
 282                 self.tcx.sess.emit_err(errors::InlineNotFnOrClosure {
 283                     attr_span: attr.span,
 284                     defn_span: span,
 285                 });
 286                 false
 287             }
 288         }
 289     }
 290
 291     /// Checks if a `#[no_coverage]` is applied directly to a function
 292     fn check_no_coverage(
 293         &self,
 294         hir_id: HirId,
 295         attr: &Attribute,
 296         span: Span,
 297         target: Target,
 298     ) -> bool {
 299         match target {
 300             // no_coverage on function is fine
 301             Target::Fn
 302             | Target::Closure
 303             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 304
 305             // function prototypes can't be covered
 306             Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
 307                 self.tcx.emit_spanned_lint(
 308                     UNUSED_ATTRIBUTES,
 309                     hir_id,
 310                     attr.span,
 311                     errors::IgnoredNoCoverageFnProto,
 312                 );
 313                 true
 314             }
 315
 316             Target::Mod | Target::ForeignMod | Target::Impl | Target::Trait => {
 317                 self.tcx.emit_spanned_lint(
 318                     UNUSED_ATTRIBUTES,
 319                     hir_id,
 320                     attr.span,
 321                     errors::IgnoredNoCoveragePropagate,
 322                 );
 323                 true
 324             }
 325
 326             Target::Expression | Target::Statement | Target::Arm => {
 327                 self.tcx.emit_spanned_lint(
 328                     UNUSED_ATTRIBUTES,
 329                     hir_id,
 330                     attr.span,
 331                     errors::IgnoredNoCoverageFnDefn,
 332                 );
 333                 true
 334             }
 335
 336             _ => {
 337                 self.tcx.sess.emit_err(errors::IgnoredNoCoverageNotCoverable {
 338                     attr_span: attr.span,
 339                     defn_span: span,
 340                 });
 341                 false
 342             }
 343         }
 344     }
 345
 346     fn check_generic_attr(
 347         &self,
 348         hir_id: HirId,
 349         attr: &Attribute,
 350         target: Target,
 351         allowed_targets: &[Target],
 352     ) {
 353         if !allowed_targets.iter().any(|t| t == &target) {
 354             let name = attr.name_or_empty();
 355             let mut i = allowed_targets.iter();
 356             // Pluralize
 357             let b = i.next().map_or_else(String::new, |t| t.to_string() + "s");
 358             let supported_names = i.enumerate().fold(b, |mut b, (i, allowed_target)| {
 359                 if allowed_targets.len() > 2 && i == allowed_targets.len() - 2 {
 360                     b.push_str(", and ");
 361                 } else if allowed_targets.len() == 2 && i == allowed_targets.len() - 2 {
 362                     b.push_str(" and ");
 363                 } else {
 364                     b.push_str(", ");
 365                 }
 366                 // Pluralize
 367                 b.push_str(&(allowed_target.to_string() + "s"));
 368                 b
 369             });
 370             self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
 371                 lint.build(&format!("`#[{name}]` only has an effect on {}", supported_names))
 372                     .emit();
 373             });
 374         }
 375     }
 376
 377     /// Checks if `#[naked]` is applied to a function definition.
 378     fn check_naked(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
 379         match target {
 380             Target::Fn
 381             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 382             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 383             // `#[allow_internal_unstable]` attribute with just a lint, because we previously
 384             // erroneously allowed it and some crates used it accidentally, to to be compatible
 385             // with crates depending on them, we can't throw an error here.
 386             Target::Field | Target::Arm | Target::MacroDef => {
 387                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "naked");
 388                 true
 389             }
 390             _ => {
 391                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
 392                     attr_span: attr.span,
 393                     defn_span: span,
 394                 });
 395                 false
 396             }
 397         }
 398     }
 399
 400     /// Checks if `#[cmse_nonsecure_entry]` is applied to a function definition.
 401     fn check_cmse_nonsecure_entry(&self, attr: &Attribute, span: Span, target: Target) -> bool {
 402         match target {
 403             Target::Fn
 404             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 405             _ => {
 406                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
 407                     attr_span: attr.span,
 408                     defn_span: span,
 409                 });
 410                 false
 411             }
 412         }
 413     }
 414
 415     /// Debugging aid for `object_lifetime_default` query.
 416     fn check_object_lifetime_default(&self, hir_id: HirId) {
 417         let tcx = self.tcx;
 418         if let Some(generics) = tcx.hir().get_generics(tcx.hir().local_def_id(hir_id)) {
 419             for p in generics.params {
 420                 let hir::GenericParamKind::Type { .. } = p.kind else { continue };
 421                 let param_id = tcx.hir().local_def_id(p.hir_id);
 422                 let default = tcx.object_lifetime_default(param_id);
 423                 let repr = match default {
 424                     ObjectLifetimeDefault::Empty => "BaseDefault".to_owned(),
 425                     ObjectLifetimeDefault::Static => "'static".to_owned(),
 426                     ObjectLifetimeDefault::Param(def_id) => tcx.item_name(def_id).to_string(),
 427                     ObjectLifetimeDefault::Ambiguous => "Ambiguous".to_owned(),
 428                 };
 429                 tcx.sess.span_err(p.span, &repr);
 430             }
 431         }
 432     }
 433
 434     /// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid.
 435     fn check_track_caller(
 436         &self,
 437         hir_id: HirId,
 438         attr_span: Span,
 439         attrs: &[Attribute],
 440         span: Span,
 441         target: Target,
 442     ) -> bool {
 443         match target {
 444             _ if attrs.iter().any(|attr| attr.has_name(sym::naked)) => {
 445                 self.tcx.sess.emit_err(errors::NakedTrackedCaller { attr_span });
 446                 false
 447             }
 448             Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => true,
 449             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 450             // `#[track_caller]` attribute with just a lint, because we previously
 451             // erroneously allowed it and some crates used it accidentally, to to be compatible
 452             // with crates depending on them, we can't throw an error here.
 453             Target::Field | Target::Arm | Target::MacroDef => {
 454                 for attr in attrs {
 455                     self.inline_attr_str_error_with_macro_def(hir_id, attr, "track_caller");
 456                 }
 457                 true
 458             }
 459             _ => {
 460                 self.tcx
 461                     .sess
 462                     .emit_err(errors::TrackedCallerWrongLocation { attr_span, defn_span: span });
 463                 false
 464             }
 465         }
 466     }
 467
 468     /// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid.
 469     fn check_non_exhaustive(
 470         &self,
 471         hir_id: HirId,
 472         attr: &Attribute,
 473         span: Span,
 474         target: Target,
 475     ) -> bool {
 476         match target {
 477             Target::Struct | Target::Enum | Target::Variant => true,
 478             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 479             // `#[non_exhaustive]` attribute with just a lint, because we previously
 480             // erroneously allowed it and some crates used it accidentally, to to be compatible
 481             // with crates depending on them, we can't throw an error here.
 482             Target::Field | Target::Arm | Target::MacroDef => {
 483                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "non_exhaustive");
 484                 true
 485             }
 486             _ => {
 487                 self.tcx.sess.emit_err(errors::NonExhaustiveWrongLocation {
 488                     attr_span: attr.span,
 489                     defn_span: span,
 490                 });
 491                 false
 492             }
 493         }
 494     }
 495
 496     /// Checks if the `#[marker]` attribute on an `item` is valid. Returns `true` if valid.
 497     fn check_marker(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
 498         match target {
 499             Target::Trait => true,
 500             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 501             // `#[marker]` attribute with just a lint, because we previously
 502             // erroneously allowed it and some crates used it accidentally, to to be compatible
 503             // with crates depending on them, we can't throw an error here.
 504             Target::Field | Target::Arm | Target::MacroDef => {
 505                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "marker");
 506                 true
 507             }
 508             _ => {
 509                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
 510                     attr_span: attr.span,
 511                     defn_span: span,
 512                 });
 513                 false
 514             }
 515         }
 516     }
 517
 518     /// Checks if the `#[rustc_must_implement_one_of]` attribute on a `target` is valid. Returns `true` if valid.
 519     fn check_rustc_must_implement_one_of(
 520         &self,
 521         attr: &Attribute,
 522         span: Span,
 523         target: Target,
 524     ) -> bool {
 525         match target {
 526             Target::Trait => true,
 527             _ => {
 528                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
 529                     attr_span: attr.span,
 530                     defn_span: span,
 531                 });
 532                 false
 533             }
 534         }
 535     }
 536
 537     /// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid.
 538     fn check_target_feature(
 539         &self,
 540         hir_id: HirId,
 541         attr: &Attribute,
 542         span: Span,
 543         target: Target,
 544     ) -> bool {
 545         match target {
 546             Target::Fn
 547             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 548             // FIXME: #[target_feature] was previously erroneously allowed on statements and some
 549             // crates used this, so only emit a warning.
 550             Target::Statement => {
 551                 self.tcx.emit_spanned_lint(
 552                     UNUSED_ATTRIBUTES,
 553                     hir_id,
 554                     attr.span,
 555                     errors::TargetFeatureOnStatement,
 556                 );
 557                 true
 558             }
 559             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 560             // `#[target_feature]` attribute with just a lint, because we previously
 561             // erroneously allowed it and some crates used it accidentally, to to be compatible
 562             // with crates depending on them, we can't throw an error here.
 563             Target::Field | Target::Arm | Target::MacroDef => {
 564                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "target_feature");
 565                 true
 566             }
 567             _ => {
 568                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
 569                     attr_span: attr.span,
 570                     defn_span: span,
 571                 });
 572                 false
 573             }
 574         }
 575     }
 576
 577     /// Checks if the `#[thread_local]` attribute on `item` is valid. Returns `true` if valid.
 578     fn check_thread_local(&self, attr: &Attribute, span: Span, target: Target) -> bool {
 579         match target {
 580             Target::ForeignStatic | Target::Static => true,
 581             _ => {
 582                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToStatic {
 583                     attr_span: attr.span,
 584                     defn_span: span,
 585                 });
 586                 false
 587             }
 588         }
 589     }
 590
 591     fn doc_attr_str_error(&self, meta: &NestedMetaItem, attr_name: &str) {
 592         self.tcx.sess.emit_err(errors::DocExpectStr { attr_span: meta.span(), attr_name });
 593     }
 594
 595     fn check_doc_alias_value(
 596         &self,
 597         meta: &NestedMetaItem,
 598         doc_alias: Symbol,
 599         hir_id: HirId,
 600         target: Target,
 601         is_list: bool,
 602         aliases: &mut FxHashMap<String, Span>,
 603     ) -> bool {
 604         let tcx = self.tcx;
 605         let span = meta.name_value_literal_span().unwrap_or_else(|| meta.span());
 606         let attr_str =
 607             &format!("`#[doc(alias{})]`", if is_list { "(\"...\")" } else { " = \"...\"" });
 608         if doc_alias == kw::Empty {
 609             tcx.sess.emit_err(errors::DocAliasEmpty { span, attr_str });
 610             return false;
 611         }
 612
 613         let doc_alias_str = doc_alias.as_str();
 614         if let Some(c) = doc_alias_str
 615             .chars()
 616             .find(|&c| c == '"' || c == '\'' || (c.is_whitespace() && c != ' '))
 617         {
 618             tcx.sess.emit_err(errors::DocAliasBadChar { span, attr_str, char_: c });
 619             return false;
 620         }
 621         if doc_alias_str.starts_with(' ') || doc_alias_str.ends_with(' ') {
 622             tcx.sess.emit_err(errors::DocAliasStartEnd { span, attr_str });
 623             return false;
 624         }
 625
 626         let span = meta.span();
 627         if let Some(location) = match target {
 628             Target::AssocTy => {
 629                 let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
 630                 let containing_item = self.tcx.hir().expect_item(parent_hir_id);
 631                 if Target::from_item(containing_item) == Target::Impl {
 632                     Some("type alias in implementation block")
 633                 } else {
 634                     None
 635                 }
 636             }
 637             Target::AssocConst => {
 638                 let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
 639                 let containing_item = self.tcx.hir().expect_item(parent_hir_id);
 640                 // We can't link to trait impl's consts.
 641                 let err = "associated constant in trait implementation block";
 642                 match containing_item.kind {
 643                     ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => Some(err),
 644                     _ => None,
 645                 }
 646             }
 647             // we check the validity of params elsewhere
 648             Target::Param => return false,
 649             Target::Expression
 650             | Target::Statement
 651             | Target::Arm
 652             | Target::ForeignMod
 653             | Target::Closure
 654             | Target::Impl => Some(target.name()),
 655             Target::ExternCrate
 656             | Target::Use
 657             | Target::Static
 658             | Target::Const
 659             | Target::Fn
 660             | Target::Mod
 661             | Target::GlobalAsm
 662             | Target::TyAlias
 663             | Target::OpaqueTy
 664             | Target::Enum
 665             | Target::Variant
 666             | Target::Struct
 667             | Target::Field
 668             | Target::Union
 669             | Target::Trait
 670             | Target::TraitAlias
 671             | Target::Method(..)
 672             | Target::ForeignFn
 673             | Target::ForeignStatic
 674             | Target::ForeignTy
 675             | Target::GenericParam(..)
 676             | Target::MacroDef
 677             | Target::PatField
 678             | Target::ExprField => None,
 679         } {
 680             tcx.sess.emit_err(errors::DocAliasBadLocation { span, attr_str, location });
 681             return false;
 682         }
 683         let item_name = self.tcx.hir().name(hir_id);
 684         if item_name == doc_alias {
 685             tcx.sess.emit_err(errors::DocAliasNotAnAlias { span, attr_str });
 686             return false;
 687         }
 688         if let Err(entry) = aliases.try_insert(doc_alias_str.to_owned(), span) {
 689             self.tcx.emit_spanned_lint(
 690                 UNUSED_ATTRIBUTES,
 691                 hir_id,
 692                 span,
 693                 errors::DocAliasDuplicated { first_defn: *entry.entry.get() },
 694             );
 695         }
 696         true
 697     }
 698
 699     fn check_doc_alias(
 700         &self,
 701         meta: &NestedMetaItem,
 702         hir_id: HirId,
 703         target: Target,
 704         aliases: &mut FxHashMap<String, Span>,
 705     ) -> bool {
 706         if let Some(values) = meta.meta_item_list() {
 707             let mut errors = 0;
 708             for v in values {
 709                 match v.literal() {
 710                     Some(l) => match l.kind {
 711                         LitKind::Str(s, _) => {
 712                             if !self.check_doc_alias_value(v, s, hir_id, target, true, aliases) {
 713                                 errors += 1;
 714                             }
 715                         }
 716                         _ => {
 717                             self.tcx
 718                                 .sess
 719                                 .emit_err(errors::DocAliasNotStringLiteral { span: v.span() });
 720                             errors += 1;
 721                         }
 722                     },
 723                     None => {
 724                         self.tcx.sess.emit_err(errors::DocAliasNotStringLiteral { span: v.span() });
 725                         errors += 1;
 726                     }
 727                 }
 728             }
 729             errors == 0
 730         } else if let Some(doc_alias) = meta.value_str() {
 731             self.check_doc_alias_value(meta, doc_alias, hir_id, target, false, aliases)
 732         } else {
 733             self.tcx.sess.emit_err(errors::DocAliasMalformed { span: meta.span() });
 734             false
 735         }
 736     }
 737
 738     fn check_doc_keyword(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 739         let doc_keyword = meta.value_str().unwrap_or(kw::Empty);
 740         if doc_keyword == kw::Empty {
 741             self.doc_attr_str_error(meta, "keyword");
 742             return false;
 743         }
 744         match self.tcx.hir().find(hir_id).and_then(|node| match node {
 745             hir::Node::Item(item) => Some(&item.kind),
 746             _ => None,
 747         }) {
 748             Some(ItemKind::Mod(ref module)) => {
 749                 if !module.item_ids.is_empty() {
 750                     self.tcx.sess.emit_err(errors::DocKeywordEmptyMod { span: meta.span() });
 751                     return false;
 752                 }
 753             }
 754             _ => {
 755                 self.tcx.sess.emit_err(errors::DocKeywordNotMod { span: meta.span() });
 756                 return false;
 757             }
 758         }
 759         if !rustc_lexer::is_ident(doc_keyword.as_str()) {
 760             self.tcx.sess.emit_err(errors::DocKeywordInvalidIdent {
 761                 span: meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
 762                 doc_keyword,
 763             });
 764             return false;
 765         }
 766         true
 767     }
 768
 769     fn check_doc_fake_variadic(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 770         match self.tcx.hir().find(hir_id).and_then(|node| match node {
 771             hir::Node::Item(item) => Some(&item.kind),
 772             _ => None,
 773         }) {
 774             Some(ItemKind::Impl(ref i)) => {
 775                 let is_valid = matches!(&i.self_ty.kind, hir::TyKind::Tup([_]))
 776                     || if let hir::TyKind::BareFn(bare_fn_ty) = &i.self_ty.kind {
 777                         bare_fn_ty.decl.inputs.len() == 1
 778                     } else {
 779                         false
 780                     };
 781                 if !is_valid {
 782                     self.tcx.sess.emit_err(errors::DocFakeVariadicNotValid { span: meta.span() });
 783                     return false;
 784                 }
 785             }
 786             _ => {
 787                 self.tcx.sess.emit_err(errors::DocKeywordOnlyImpl { span: meta.span() });
 788                 return false;
 789             }
 790         }
 791         true
 792     }
 793
 794     /// Checks `#[doc(inline)]`/`#[doc(no_inline)]` attributes. Returns `true` if valid.
 795     ///
 796     /// A doc inlining attribute is invalid if it is applied to a non-`use` item, or
 797     /// if there are conflicting attributes for one item.
 798     ///
 799     /// `specified_inline` is used to keep track of whether we have
 800     /// already seen an inlining attribute for this item.
 801     /// If so, `specified_inline` holds the value and the span of
 802     /// the first `inline`/`no_inline` attribute.
 803     fn check_doc_inline(
 804         &self,
 805         attr: &Attribute,
 806         meta: &NestedMetaItem,
 807         hir_id: HirId,
 808         target: Target,
 809         specified_inline: &mut Option<(bool, Span)>,
 810     ) -> bool {
 811         if target == Target::Use || target == Target::ExternCrate {
 812             let do_inline = meta.name_or_empty() == sym::inline;
 813             if let Some((prev_inline, prev_span)) = *specified_inline {
 814                 if do_inline != prev_inline {
 815                     let mut spans = MultiSpan::from_spans(vec![prev_span, meta.span()]);
 816                     spans.push_span_label(prev_span, fluent::passes::doc_inline_conflict_first);
 817                     spans.push_span_label(meta.span(), fluent::passes::doc_inline_conflict_second);
 818                     self.tcx.sess.emit_err(errors::DocKeywordConflict { spans });
 819                     return false;
 820                 }
 821                 true
 822             } else {
 823                 *specified_inline = Some((do_inline, meta.span()));
 824                 true
 825             }
 826         } else {
 827             self.tcx.emit_spanned_lint(
 828                 INVALID_DOC_ATTRIBUTES,
 829                 hir_id,
 830                 meta.span(),
 831                 errors::DocInlineOnlyUse {
 832                     attr_span: meta.span(),
 833                     item_span: (attr.style == AttrStyle::Outer)
 834                         .then(|| self.tcx.hir().span(hir_id)),
 835                 },
 836             );
 837             false
 838         }
 839     }
 840
 841     /// Checks that an attribute is *not* used at the crate level. Returns `true` if valid.
 842     fn check_attr_not_crate_level(
 843         &self,
 844         meta: &NestedMetaItem,
 845         hir_id: HirId,
 846         attr_name: &str,
 847     ) -> bool {
 848         if CRATE_HIR_ID == hir_id {
 849             self.tcx.sess.emit_err(errors::DocAttrNotCrateLevel { span: meta.span(), attr_name });
 850             return false;
 851         }
 852         true
 853     }
 854
 855     /// Checks that an attribute is used at the crate level. Returns `true` if valid.
 856     fn check_attr_crate_level(
 857         &self,
 858         attr: &Attribute,
 859         meta: &NestedMetaItem,
 860         hir_id: HirId,
 861     ) -> bool {
 862         if hir_id != CRATE_HIR_ID {
 863             self.tcx.struct_span_lint_hir(INVALID_DOC_ATTRIBUTES, hir_id, meta.span(), |lint| {
 864                 let mut err = lint.build(fluent::passes::attr_crate_level);
 865                 if attr.style == AttrStyle::Outer
 866                     && self.tcx.hir().get_parent_item(hir_id) == CRATE_DEF_ID
 867                 {
 868                     if let Ok(mut src) = self.tcx.sess.source_map().span_to_snippet(attr.span) {
 869                         src.insert(1, '!');
 870                         err.span_suggestion_verbose(
 871                             attr.span,
 872                             fluent::passes::suggestion,
 873                             src,
 874                             Applicability::MaybeIncorrect,
 875                         );
 876                     } else {
 877                         err.span_help(attr.span, fluent::passes::help);
 878                     }
 879                 }
 880                 err.note(fluent::passes::note).emit();
 881             });
 882             return false;
 883         }
 884         true
 885     }
 886
 887     /// Checks that `doc(test(...))` attribute contains only valid attributes. Returns `true` if
 888     /// valid.
 889     fn check_test_attr(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 890         let mut is_valid = true;
 891         if let Some(metas) = meta.meta_item_list() {
 892             for i_meta in metas {
 893                 match i_meta.name_or_empty() {
 894                     sym::attr | sym::no_crate_inject => {}
 895                     _ => {
 896                         self.tcx.emit_spanned_lint(
 897                             INVALID_DOC_ATTRIBUTES,
 898                             hir_id,
 899                             i_meta.span(),
 900                             errors::DocTestUnknown {
 901                                 path: rustc_ast_pretty::pprust::path_to_string(
 902                                     &i_meta.meta_item().unwrap().path,
 903                                 ),
 904                             },
 905                         );
 906                         is_valid = false;
 907                     }
 908                 }
 909             }
 910         } else {
 911             self.tcx.emit_spanned_lint(
 912                 INVALID_DOC_ATTRIBUTES,
 913                 hir_id,
 914                 meta.span(),
 915                 errors::DocTestTakesList,
 916             );
 917             is_valid = false;
 918         }
 919         is_valid
 920     }
 921
 922     /// Runs various checks on `#[doc]` attributes. Returns `true` if valid.
 923     ///
 924     /// `specified_inline` should be initialized to `None` and kept for the scope
 925     /// of one item. Read the documentation of [`check_doc_inline`] for more information.
 926     ///
 927     /// [`check_doc_inline`]: Self::check_doc_inline
 928     fn check_doc_attrs(
 929         &self,
 930         attr: &Attribute,
 931         hir_id: HirId,
 932         target: Target,
 933         specified_inline: &mut Option<(bool, Span)>,
 934         aliases: &mut FxHashMap<String, Span>,
 935     ) -> bool {
 936         let mut is_valid = true;
 937
 938         if let Some(mi) = attr.meta() && let Some(list) = mi.meta_item_list() {
 939             for meta in list {
 940                 if let Some(i_meta) = meta.meta_item() {
 941                     match i_meta.name_or_empty() {
 942                         sym::alias
 943                             if !self.check_attr_not_crate_level(meta, hir_id, "alias")
 944                                 || !self.check_doc_alias(meta, hir_id, target, aliases) =>
 945                         {
 946                             is_valid = false
 947                         }
 948
 949                         sym::keyword
 950                             if !self.check_attr_not_crate_level(meta, hir_id, "keyword")
 951                                 || !self.check_doc_keyword(meta, hir_id) =>
 952                         {
 953                             is_valid = false
 954                         }
 955
 956                         sym::fake_variadic
 957                             if !self.check_attr_not_crate_level(meta, hir_id, "fake_variadic")
 958                                 || !self.check_doc_fake_variadic(meta, hir_id) =>
 959                         {
 960                             is_valid = false
 961                         }
 962
 963                         sym::html_favicon_url
 964                         | sym::html_logo_url
 965                         | sym::html_playground_url
 966                         | sym::issue_tracker_base_url
 967                         | sym::html_root_url
 968                         | sym::html_no_source
 969                         | sym::test
 970                             if !self.check_attr_crate_level(attr, meta, hir_id) =>
 971                         {
 972                             is_valid = false;
 973                         }
 974
 975                         sym::inline | sym::no_inline
 976                             if !self.check_doc_inline(
 977                                 attr,
 978                                 meta,
 979                                 hir_id,
 980                                 target,
 981                                 specified_inline,
 982                             ) =>
 983                         {
 984                             is_valid = false;
 985                         }
 986
 987                         // no_default_passes: deprecated
 988                         // passes: deprecated
 989                         // plugins: removed, but rustdoc warns about it itself
 990                         sym::alias
 991                         | sym::cfg
 992                         | sym::cfg_hide
 993                         | sym::hidden
 994                         | sym::html_favicon_url
 995                         | sym::html_logo_url
 996                         | sym::html_no_source
 997                         | sym::html_playground_url
 998                         | sym::html_root_url
 999                         | sym::inline
1000                         | sym::issue_tracker_base_url
1001                         | sym::keyword
1002                         | sym::masked
1003                         | sym::no_default_passes
1004                         | sym::no_inline
1005                         | sym::notable_trait
1006                         | sym::passes
1007                         | sym::plugins
1008                         | sym::fake_variadic => {}
1009
1010                         sym::test => {
1011                             if !self.check_test_attr(meta, hir_id) {
1012                                 is_valid = false;
1013                             }
1014                         }
1015
1016                         sym::primitive => {
1017                             if !self.tcx.features().rustdoc_internals {
1018                                 self.tcx.emit_spanned_lint(
1019                                     INVALID_DOC_ATTRIBUTES,
1020                                     hir_id,
1021                                     i_meta.span,
1022                                     errors::DocPrimitive,
1023                                 );
1024                             }
1025                         }
1026
1027                         _ => {
1028                             let path = rustc_ast_pretty::pprust::path_to_string(&i_meta.path);
1029                             if i_meta.has_name(sym::spotlight) {
1030                                 self.tcx.emit_spanned_lint(
1031                                     INVALID_DOC_ATTRIBUTES,
1032                                     hir_id,
1033                                     i_meta.span,
1034                                     errors::DocTestUnknownSpotlight {
1035                                         path,
1036                                         span: i_meta.span
1037                                     }
1038                                 );
1039                             } else if i_meta.has_name(sym::include) &&
1040                                     let Some(value) = i_meta.value_str() {
1041                                 let applicability = if list.len() == 1 {
1042                                     Applicability::MachineApplicable
1043                                 } else {
1044                                     Applicability::MaybeIncorrect
1045                                 };
1046                                 // If there are multiple attributes, the suggestion would suggest
1047                                 // deleting all of them, which is incorrect.
1048                                 self.tcx.emit_spanned_lint(
1049                                     INVALID_DOC_ATTRIBUTES,
1050                                     hir_id,
1051                                     i_meta.span,
1052                                     errors::DocTestUnknownInclude {
1053                                         path,
1054                                         value: value.to_string(),
1055                                         inner: (attr.style == AttrStyle::Inner)
1056                                             .then_some("!")
1057                                             .unwrap_or(""),
1058                                         sugg: (attr.meta().unwrap().span, applicability),
1059                                     }
1060                                 );
1061                             } else {
1062                                 self.tcx.emit_spanned_lint(
1063                                     INVALID_DOC_ATTRIBUTES,
1064                                     hir_id,
1065                                     i_meta.span,
1066                                     errors::DocTestUnknownAny { path }
1067                                 );
1068                             }
1069                             is_valid = false;
1070                         }
1071                     }
1072                 } else {
1073                     self.tcx.emit_spanned_lint(
1074                         INVALID_DOC_ATTRIBUTES,
1075                         hir_id,
1076                         meta.span(),
1077                         errors::DocInvalid,
1078                     );
1079                     is_valid = false;
1080                 }
1081             }
1082         }
1083
1084         is_valid
1085     }
1086
1087     /// Warns against some misuses of `#[pass_by_value]`
1088     fn check_pass_by_value(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1089         match target {
1090             Target::Struct | Target::Enum | Target::TyAlias => true,
1091             _ => {
1092                 self.tcx.sess.emit_err(errors::PassByValue { attr_span: attr.span, span });
1093                 false
1094             }
1095         }
1096     }
1097
1098     fn check_allow_incoherent_impl(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1099         match target {
1100             Target::Method(MethodKind::Inherent) => true,
1101             _ => {
1102                 self.tcx.sess.emit_err(errors::AllowIncoherentImpl { attr_span: attr.span, span });
1103                 false
1104             }
1105         }
1106     }
1107
1108     fn check_has_incoherent_inherent_impls(
1109         &self,
1110         attr: &Attribute,
1111         span: Span,
1112         target: Target,
1113     ) -> bool {
1114         match target {
1115             Target::Trait | Target::Struct | Target::Enum | Target::Union | Target::ForeignTy => {
1116                 true
1117             }
1118             _ => {
1119                 self.tcx
1120                     .sess
1121                     .emit_err(errors::HasIncoherentInherentImpl { attr_span: attr.span, span });
1122                 false
1123             }
1124         }
1125     }
1126
1127     /// Warns against some misuses of `#[must_use]`
1128     fn check_must_use(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
1129         let node = self.tcx.hir().get(hir_id);
1130         if let Some(kind) = node.fn_kind() && let rustc_hir::IsAsync::Async = kind.asyncness() {
1131             self.tcx.emit_spanned_lint(
1132                 UNUSED_ATTRIBUTES,
1133                 hir_id,
1134                 attr.span,
1135                 errors::MustUseAsync { span }
1136             );
1137         }
1138
1139         if !matches!(
1140             target,
1141             Target::Fn
1142                 | Target::Enum
1143                 | Target::Struct
1144                 | Target::Union
1145                 | Target::Method(_)
1146                 | Target::ForeignFn
1147                 // `impl Trait` in return position can trip
1148                 // `unused_must_use` if `Trait` is marked as
1149                 // `#[must_use]`
1150                 | Target::Trait
1151         ) {
1152             let article = match target {
1153                 Target::ExternCrate
1154                 | Target::OpaqueTy
1155                 | Target::Enum
1156                 | Target::Impl
1157                 | Target::Expression
1158                 | Target::Arm
1159                 | Target::AssocConst
1160                 | Target::AssocTy => "an",
1161                 _ => "a",
1162             };
1163
1164             self.tcx.emit_spanned_lint(
1165                 UNUSED_ATTRIBUTES,
1166                 hir_id,
1167                 attr.span,
1168                 errors::MustUseNoEffect { article, target },
1169             );
1170         }
1171
1172         // For now, its always valid
1173         true
1174     }
1175
1176     /// Checks if `#[must_not_suspend]` is applied to a function. Returns `true` if valid.
1177     fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1178         match target {
1179             Target::Struct | Target::Enum | Target::Union | Target::Trait => true,
1180             _ => {
1181                 self.tcx.sess.emit_err(errors::MustNotSuspend { attr_span: attr.span, span });
1182                 false
1183             }
1184         }
1185     }
1186
1187     /// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid.
1188     fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1189         match target {
1190             Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => {}
1191             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1192             // `#[cold]` attribute with just a lint, because we previously
1193             // erroneously allowed it and some crates used it accidentally, to to be compatible
1194             // with crates depending on them, we can't throw an error here.
1195             Target::Field | Target::Arm | Target::MacroDef => {
1196                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "cold");
1197             }
1198             _ => {
1199                 // FIXME: #[cold] was previously allowed on non-functions and some crates used
1200                 // this, so only emit a warning.
1201                 self.tcx.emit_spanned_lint(
1202                     UNUSED_ATTRIBUTES,
1203                     hir_id,
1204                     attr.span,
1205                     errors::Cold { span },
1206                 );
1207             }
1208         }
1209     }
1210
1211     /// Checks if `#[link]` is applied to an item other than a foreign module.
1212     fn check_link(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1213         if target == Target::ForeignMod
1214             && let hir::Node::Item(item) = self.tcx.hir().get(hir_id)
1215             && let Item { kind: ItemKind::ForeignMod { abi, .. }, .. } = item
1216             && !matches!(abi, Abi::Rust | Abi::RustIntrinsic | Abi::PlatformIntrinsic)
1217         {
1218             return;
1219         }
1220
1221         self.tcx.emit_spanned_lint(
1222             UNUSED_ATTRIBUTES,
1223             hir_id,
1224             attr.span,
1225             errors::Link { span: (target != Target::ForeignMod).then_some(span) },
1226         );
1227     }
1228
1229     /// Checks if `#[link_name]` is applied to an item other than a foreign function or static.
1230     fn check_link_name(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1231         match target {
1232             Target::ForeignFn | Target::ForeignStatic => {}
1233             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1234             // `#[link_name]` attribute with just a lint, because we previously
1235             // erroneously allowed it and some crates used it accidentally, to to be compatible
1236             // with crates depending on them, we can't throw an error here.
1237             Target::Field | Target::Arm | Target::MacroDef => {
1238                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_name");
1239             }
1240             _ => {
1241                 // FIXME: #[cold] was previously allowed on non-functions/statics and some crates
1242                 // used this, so only emit a warning.
1243                 let attr_span = matches!(target, Target::ForeignMod).then_some(attr.span);
1244                 if let Some(s) = attr.value_str() {
1245                     self.tcx.emit_spanned_lint(
1246                         UNUSED_ATTRIBUTES,
1247                         hir_id,
1248                         attr.span,
1249                         errors::LinkName { span, attr_span, value: s.as_str() },
1250                     );
1251                 } else {
1252                     self.tcx.emit_spanned_lint(
1253                         UNUSED_ATTRIBUTES,
1254                         hir_id,
1255                         attr.span,
1256                         errors::LinkName { span, attr_span, value: "..." },
1257                     );
1258                 };
1259             }
1260         }
1261     }
1262
1263     /// Checks if `#[no_link]` is applied to an `extern crate`. Returns `true` if valid.
1264     fn check_no_link(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
1265         match target {
1266             Target::ExternCrate => true,
1267             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1268             // `#[no_link]` attribute with just a lint, because we previously
1269             // erroneously allowed it and some crates used it accidentally, to to be compatible
1270             // with crates depending on them, we can't throw an error here.
1271             Target::Field | Target::Arm | Target::MacroDef => {
1272                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_link");
1273                 true
1274             }
1275             _ => {
1276                 self.tcx.sess.emit_err(errors::NoLink { attr_span: attr.span, span });
1277                 false
1278             }
1279         }
1280     }
1281
1282     fn is_impl_item(&self, hir_id: HirId) -> bool {
1283         matches!(self.tcx.hir().get(hir_id), hir::Node::ImplItem(..))
1284     }
1285
1286     /// Checks if `#[export_name]` is applied to a function or static. Returns `true` if valid.
1287     fn check_export_name(
1288         &self,
1289         hir_id: HirId,
1290         attr: &Attribute,
1291         span: Span,
1292         target: Target,
1293     ) -> bool {
1294         match target {
1295             Target::Static | Target::Fn => true,
1296             Target::Method(..) if self.is_impl_item(hir_id) => true,
1297             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1298             // `#[export_name]` attribute with just a lint, because we previously
1299             // erroneously allowed it and some crates used it accidentally, to to be compatible
1300             // with crates depending on them, we can't throw an error here.
1301             Target::Field | Target::Arm | Target::MacroDef => {
1302                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "export_name");
1303                 true
1304             }
1305             _ => {
1306                 self.tcx.sess.emit_err(errors::ExportName { attr_span: attr.span, span });
1307                 false
1308             }
1309         }
1310     }
1311
1312     fn check_rustc_layout_scalar_valid_range(
1313         &self,
1314         attr: &Attribute,
1315         span: Span,
1316         target: Target,
1317     ) -> bool {
1318         if target != Target::Struct {
1319             self.tcx.sess.emit_err(errors::RustcLayoutScalarValidRangeNotStruct {
1320                 attr_span: attr.span,
1321                 span,
1322             });
1323             return false;
1324         }
1325
1326         let Some(list) = attr.meta_item_list() else {
1327             return false;
1328         };
1329
1330         if matches!(&list[..], &[NestedMetaItem::Literal(Lit { kind: LitKind::Int(..), .. })]) {
1331             true
1332         } else {
1333             self.tcx.sess.emit_err(errors::RustcLayoutScalarValidRangeArg { attr_span: attr.span });
1334             false
1335         }
1336     }
1337
1338     /// Checks if `#[rustc_legacy_const_generics]` is applied to a function and has a valid argument.
1339     fn check_rustc_legacy_const_generics(
1340         &self,
1341         attr: &Attribute,
1342         span: Span,
1343         target: Target,
1344         item: Option<ItemLike<'_>>,
1345     ) -> bool {
1346         let is_function = matches!(target, Target::Fn);
1347         if !is_function {
1348             self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
1349                 attr_span: attr.span,
1350                 defn_span: span,
1351             });
1352             return false;
1353         }
1354
1355         let Some(list) = attr.meta_item_list() else {
1356             // The attribute form is validated on AST.
1357             return false;
1358         };
1359
1360         let Some(ItemLike::Item(Item {
1361             kind: ItemKind::Fn(FnSig { decl, .. }, generics, _),
1362             ..
1363         }))  = item else {
1364             bug!("should be a function item");
1365         };
1366
1367         for param in generics.params {
1368             match param.kind {
1369                 hir::GenericParamKind::Const { .. } => {}
1370                 _ => {
1371                     self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsOnly {
1372                         attr_span: attr.span,
1373                         param_span: param.span,
1374                     });
1375                     return false;
1376                 }
1377             }
1378         }
1379
1380         if list.len() != generics.params.len() {
1381             self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndex {
1382                 attr_span: attr.span,
1383                 generics_span: generics.span,
1384             });
1385             return false;
1386         }
1387
1388         let arg_count = decl.inputs.len() as u128 + generics.params.len() as u128;
1389         let mut invalid_args = vec![];
1390         for meta in list {
1391             if let Some(LitKind::Int(val, _)) = meta.literal().map(|lit| &lit.kind) {
1392                 if *val >= arg_count {
1393                     let span = meta.span();
1394                     self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndexExceed {
1395                         span,
1396                         arg_count: arg_count as usize,
1397                     });
1398                     return false;
1399                 }
1400             } else {
1401                 invalid_args.push(meta.span());
1402             }
1403         }
1404
1405         if !invalid_args.is_empty() {
1406             self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndexNegative { invalid_args });
1407             false
1408         } else {
1409             true
1410         }
1411     }
1412
1413     /// Helper function for checking that the provided attribute is only applied to a function or
1414     /// method.
1415     fn check_applied_to_fn_or_method(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1416         let is_function = matches!(target, Target::Fn | Target::Method(..));
1417         if !is_function {
1418             self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
1419                 attr_span: attr.span,
1420                 defn_span: span,
1421             });
1422             false
1423         } else {
1424             true
1425         }
1426     }
1427
1428     /// Checks that the `#[rustc_lint_query_instability]` attribute is only applied to a function
1429     /// or method.
1430     fn check_rustc_lint_query_instability(
1431         &self,
1432         attr: &Attribute,
1433         span: Span,
1434         target: Target,
1435     ) -> bool {
1436         self.check_applied_to_fn_or_method(attr, span, target)
1437     }
1438
1439     /// Checks that the `#[rustc_lint_diagnostics]` attribute is only applied to a function or
1440     /// method.
1441     fn check_rustc_lint_diagnostics(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1442         self.check_applied_to_fn_or_method(attr, span, target)
1443     }
1444
1445     /// Checks that the `#[rustc_lint_opt_ty]` attribute is only applied to a struct.
1446     fn check_rustc_lint_opt_ty(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1447         match target {
1448             Target::Struct => true,
1449             _ => {
1450                 self.tcx.sess.emit_err(errors::RustcLintOptTy { attr_span: attr.span, span });
1451                 false
1452             }
1453         }
1454     }
1455
1456     /// Checks that the `#[rustc_lint_opt_deny_field_access]` attribute is only applied to a field.
1457     fn check_rustc_lint_opt_deny_field_access(
1458         &self,
1459         attr: &Attribute,
1460         span: Span,
1461         target: Target,
1462     ) -> bool {
1463         match target {
1464             Target::Field => true,
1465             _ => {
1466                 self.tcx
1467                     .sess
1468                     .emit_err(errors::RustcLintOptDenyFieldAccess { attr_span: attr.span, span });
1469                 false
1470             }
1471         }
1472     }
1473
1474     /// Checks that the dep-graph debugging attributes are only present when the query-dep-graph
1475     /// option is passed to the compiler.
1476     fn check_rustc_dirty_clean(&self, attr: &Attribute) -> bool {
1477         if self.tcx.sess.opts.unstable_opts.query_dep_graph {
1478             true
1479         } else {
1480             self.tcx.sess.emit_err(errors::RustcDirtyClean { span: attr.span });
1481             false
1482         }
1483     }
1484
1485     /// Checks if `#[link_section]` is applied to a function or static.
1486     fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1487         match target {
1488             Target::Static | Target::Fn | Target::Method(..) => {}
1489             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1490             // `#[link_section]` attribute with just a lint, because we previously
1491             // erroneously allowed it and some crates used it accidentally, to to be compatible
1492             // with crates depending on them, we can't throw an error here.
1493             Target::Field | Target::Arm | Target::MacroDef => {
1494                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_section");
1495             }
1496             _ => {
1497                 // FIXME: #[link_section] was previously allowed on non-functions/statics and some
1498                 // crates used this, so only emit a warning.
1499                 self.tcx.emit_spanned_lint(
1500                     UNUSED_ATTRIBUTES,
1501                     hir_id,
1502                     attr.span,
1503                     errors::LinkSection { span },
1504                 );
1505             }
1506         }
1507     }
1508
1509     /// Checks if `#[no_mangle]` is applied to a function or static.
1510     fn check_no_mangle(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1511         match target {
1512             Target::Static | Target::Fn => {}
1513             Target::Method(..) if self.is_impl_item(hir_id) => {}
1514             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1515             // `#[no_mangle]` attribute with just a lint, because we previously
1516             // erroneously allowed it and some crates used it accidentally, to to be compatible
1517             // with crates depending on them, we can't throw an error here.
1518             Target::Field | Target::Arm | Target::MacroDef => {
1519                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_mangle");
1520             }
1521             // FIXME: #[no_mangle] was previously allowed on non-functions/statics, this should be an error
1522             // The error should specify that the item that is wrong is specifically a *foreign* fn/static
1523             // otherwise the error seems odd
1524             Target::ForeignFn | Target::ForeignStatic => {
1525                 let foreign_item_kind = match target {
1526                     Target::ForeignFn => "function",
1527                     Target::ForeignStatic => "static",
1528                     _ => unreachable!(),
1529                 };
1530                 self.tcx.emit_spanned_lint(
1531                     UNUSED_ATTRIBUTES,
1532                     hir_id,
1533                     attr.span,
1534                     errors::NoMangleForeign { span, attr_span: attr.span, foreign_item_kind },
1535                 );
1536             }
1537             _ => {
1538                 // FIXME: #[no_mangle] was previously allowed on non-functions/statics and some
1539                 // crates used this, so only emit a warning.
1540                 self.tcx.emit_spanned_lint(
1541                     UNUSED_ATTRIBUTES,
1542                     hir_id,
1543                     attr.span,
1544                     errors::NoMangle { span },
1545                 );
1546             }
1547         }
1548     }
1549
1550     /// Checks if the `#[repr]` attributes on `item` are valid.
1551     fn check_repr(
1552         &self,
1553         attrs: &[Attribute],
1554         span: Span,
1555         target: Target,
1556         item: Option<ItemLike<'_>>,
1557         hir_id: HirId,
1558     ) {
1559         // Extract the names of all repr hints, e.g., [foo, bar, align] for:
1560         // ```
1561         // #[repr(foo)]
1562         // #[repr(bar, align(8))]
1563         // ```
1564         let hints: Vec<_> = attrs
1565             .iter()
1566             .filter(|attr| attr.has_name(sym::repr))
1567             .filter_map(|attr| attr.meta_item_list())
1568             .flatten()
1569             .collect();
1570
1571         let mut int_reprs = 0;
1572         let mut is_c = false;
1573         let mut is_simd = false;
1574         let mut is_transparent = false;
1575
1576         for hint in &hints {
1577             if !hint.is_meta_item() {
1578                 self.tcx.sess.emit_err(errors::ReprIdent { span: hint.span() });
1579                 continue;
1580             }
1581
1582             let (article, allowed_targets) = match hint.name_or_empty() {
1583                 sym::C => {
1584                     is_c = true;
1585                     match target {
1586                         Target::Struct | Target::Union | Target::Enum => continue,
1587                         _ => ("a", "struct, enum, or union"),
1588                     }
1589                 }
1590                 sym::align => {
1591                     if let (Target::Fn, false) = (target, self.tcx.features().fn_align) {
1592                         feature_err(
1593                             &self.tcx.sess.parse_sess,
1594                             sym::fn_align,
1595                             hint.span(),
1596                             "`repr(align)` attributes on functions are unstable",
1597                         )
1598                         .emit();
1599                     }
1600
1601                     match target {
1602                         Target::Struct | Target::Union | Target::Enum | Target::Fn => continue,
1603                         _ => ("a", "struct, enum, function, or union"),
1604                     }
1605                 }
1606                 sym::packed => {
1607                     if target != Target::Struct && target != Target::Union {
1608                         ("a", "struct or union")
1609                     } else {
1610                         continue;
1611                     }
1612                 }
1613                 sym::simd => {
1614                     is_simd = true;
1615                     if target != Target::Struct {
1616                         ("a", "struct")
1617                     } else {
1618                         continue;
1619                     }
1620                 }
1621                 sym::transparent => {
1622                     is_transparent = true;
1623                     match target {
1624                         Target::Struct | Target::Union | Target::Enum => continue,
1625                         _ => ("a", "struct, enum, or union"),
1626                     }
1627                 }
1628                 sym::i8
1629                 | sym::u8
1630                 | sym::i16
1631                 | sym::u16
1632                 | sym::i32
1633                 | sym::u32
1634                 | sym::i64
1635                 | sym::u64
1636                 | sym::i128
1637                 | sym::u128
1638                 | sym::isize
1639                 | sym::usize => {
1640                     int_reprs += 1;
1641                     if target != Target::Enum {
1642                         ("an", "enum")
1643                     } else {
1644                         continue;
1645                     }
1646                 }
1647                 _ => {
1648                     struct_span_err!(
1649                         self.tcx.sess,
1650                         hint.span(),
1651                         E0552,
1652                         "unrecognized representation hint"
1653                     )
1654                     .emit();
1655
1656                     continue;
1657                 }
1658             };
1659
1660             struct_span_err!(
1661                 self.tcx.sess,
1662                 hint.span(),
1663                 E0517,
1664                 "{}",
1665                 &format!("attribute should be applied to {article} {allowed_targets}")
1666             )
1667             .span_label(span, &format!("not {article} {allowed_targets}"))
1668             .emit();
1669         }
1670
1671         // Just point at all repr hints if there are any incompatibilities.
1672         // This is not ideal, but tracking precisely which ones are at fault is a huge hassle.
1673         let hint_spans = hints.iter().map(|hint| hint.span());
1674
1675         // Error on repr(transparent, <anything else>).
1676         if is_transparent && hints.len() > 1 {
1677             let hint_spans: Vec<_> = hint_spans.clone().collect();
1678             struct_span_err!(
1679                 self.tcx.sess,
1680                 hint_spans,
1681                 E0692,
1682                 "transparent {} cannot have other repr hints",
1683                 target
1684             )
1685             .emit();
1686         }
1687         // Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8)
1688         if (int_reprs > 1)
1689             || (is_simd && is_c)
1690             || (int_reprs == 1
1691                 && is_c
1692                 && item.map_or(false, |item| {
1693                     if let ItemLike::Item(item) = item {
1694                         return is_c_like_enum(item);
1695                     }
1696                     return false;
1697                 }))
1698         {
1699             self.tcx.emit_spanned_lint(
1700                 CONFLICTING_REPR_HINTS,
1701                 hir_id,
1702                 hint_spans.collect::<Vec<Span>>(),
1703                 errors::ReprConflicting,
1704             );
1705         }
1706     }
1707
1708     fn check_used(&self, attrs: &[Attribute], target: Target) {
1709         let mut used_linker_span = None;
1710         let mut used_compiler_span = None;
1711         for attr in attrs.iter().filter(|attr| attr.has_name(sym::used)) {
1712             if target != Target::Static {
1713                 self.tcx.sess.emit_err(errors::UsedStatic { span: attr.span });
1714             }
1715             let inner = attr.meta_item_list();
1716             match inner.as_deref() {
1717                 Some([item]) if item.has_name(sym::linker) => {
1718                     if used_linker_span.is_none() {
1719                         used_linker_span = Some(attr.span);
1720                     }
1721                 }
1722                 Some([item]) if item.has_name(sym::compiler) => {
1723                     if used_compiler_span.is_none() {
1724                         used_compiler_span = Some(attr.span);
1725                     }
1726                 }
1727                 Some(_) => {
1728                     // This error case is handled in rustc_typeck::collect.
1729                 }
1730                 None => {
1731                     // Default case (compiler) when arg isn't defined.
1732                     if used_compiler_span.is_none() {
1733                         used_compiler_span = Some(attr.span);
1734                     }
1735                 }
1736             }
1737         }
1738         if let (Some(linker_span), Some(compiler_span)) = (used_linker_span, used_compiler_span) {
1739             self.tcx
1740                 .sess
1741                 .emit_err(errors::UsedCompilerLinker { spans: vec![linker_span, compiler_span] });
1742         }
1743     }
1744
1745     /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
1746     /// (Allows proc_macro functions)
1747     fn check_allow_internal_unstable(
1748         &self,
1749         hir_id: HirId,
1750         attr: &Attribute,
1751         span: Span,
1752         target: Target,
1753         attrs: &[Attribute],
1754     ) -> bool {
1755         debug!("Checking target: {:?}", target);
1756         match target {
1757             Target::Fn => {
1758                 for attr in attrs {
1759                     if self.tcx.sess.is_proc_macro_attr(attr) {
1760                         debug!("Is proc macro attr");
1761                         return true;
1762                     }
1763                 }
1764                 debug!("Is not proc macro attr");
1765                 false
1766             }
1767             Target::MacroDef => true,
1768             // FIXME(#80564): We permit struct fields and match arms to have an
1769             // `#[allow_internal_unstable]` attribute with just a lint, because we previously
1770             // erroneously allowed it and some crates used it accidentally, to to be compatible
1771             // with crates depending on them, we can't throw an error here.
1772             Target::Field | Target::Arm => {
1773                 self.inline_attr_str_error_without_macro_def(
1774                     hir_id,
1775                     attr,
1776                     "allow_internal_unstable",
1777                 );
1778                 true
1779             }
1780             _ => {
1781                 self.tcx
1782                     .sess
1783                     .emit_err(errors::AllowInternalUnstable { attr_span: attr.span, span });
1784                 false
1785             }
1786         }
1787     }
1788
1789     /// Checks if the items on the `#[debugger_visualizer]` attribute are valid.
1790     fn check_debugger_visualizer(&self, attr: &Attribute, target: Target) -> bool {
1791         match target {
1792             Target::Mod => {}
1793             _ => {
1794                 self.tcx.sess.emit_err(errors::DebugVisualizerPlacement { span: attr.span });
1795                 return false;
1796             }
1797         }
1798
1799         let Some(hints) = attr.meta_item_list() else {
1800             self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: attr.span });
1801             return false;
1802         };
1803
1804         let hint = match hints.len() {
1805             1 => &hints[0],
1806             _ => {
1807                 self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: attr.span });
1808                 return false;
1809             }
1810         };
1811
1812         let Some(meta_item) = hint.meta_item() else {
1813             self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: attr.span });
1814             return false;
1815         };
1816
1817         let visualizer_path = match (meta_item.name_or_empty(), meta_item.value_str()) {
1818             (sym::natvis_file, Some(value)) => value,
1819             (sym::gdb_script_file, Some(value)) => value,
1820             (_, _) => {
1821                 self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: meta_item.span });
1822                 return false;
1823             }
1824         };
1825
1826         let file =
1827             match resolve_path(&self.tcx.sess.parse_sess, visualizer_path.as_str(), attr.span) {
1828                 Ok(file) => file,
1829                 Err(mut err) => {
1830                     err.emit();
1831                     return false;
1832                 }
1833             };
1834
1835         match std::fs::File::open(&file) {
1836             Ok(_) => true,
1837             Err(err) => {
1838                 self.tcx
1839                     .sess
1840                     .struct_span_err(
1841                         meta_item.span,
1842                         &format!("couldn't read {}: {}", file.display(), err),
1843                     )
1844                     .emit();
1845                 false
1846             }
1847         }
1848     }
1849
1850     /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
1851     /// (Allows proc_macro functions)
1852     fn check_rustc_allow_const_fn_unstable(
1853         &self,
1854         hir_id: HirId,
1855         attr: &Attribute,
1856         span: Span,
1857         target: Target,
1858     ) -> bool {
1859         match target {
1860             Target::Fn | Target::Method(_)
1861                 if self.tcx.is_const_fn_raw(self.tcx.hir().local_def_id(hir_id).to_def_id()) =>
1862             {
1863                 true
1864             }
1865             // FIXME(#80564): We permit struct fields and match arms to have an
1866             // `#[allow_internal_unstable]` attribute with just a lint, because we previously
1867             // erroneously allowed it and some crates used it accidentally, to to be compatible
1868             // with crates depending on them, we can't throw an error here.
1869             Target::Field | Target::Arm | Target::MacroDef => {
1870                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "allow_internal_unstable");
1871                 true
1872             }
1873             _ => {
1874                 self.tcx
1875                     .sess
1876                     .emit_err(errors::RustcAllowConstFnUnstable { attr_span: attr.span, span });
1877                 false
1878             }
1879         }
1880     }
1881
1882     fn check_rustc_std_internal_symbol(
1883         &self,
1884         attr: &Attribute,
1885         span: Span,
1886         target: Target,
1887     ) -> bool {
1888         match target {
1889             Target::Fn | Target::Static => true,
1890             _ => {
1891                 self.tcx
1892                     .sess
1893                     .emit_err(errors::RustcStdInternalSymbol { attr_span: attr.span, span });
1894                 false
1895             }
1896         }
1897     }
1898
1899     /// `#[const_trait]` only applies to traits.
1900     fn check_const_trait(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
1901         match target {
1902             Target::Trait => true,
1903             _ => {
1904                 self.tcx.sess.emit_err(errors::ConstTrait { attr_span: attr.span });
1905                 false
1906             }
1907         }
1908     }
1909
1910     fn check_stability_promotable(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
1911         match target {
1912             Target::Expression => {
1913                 self.tcx.sess.emit_err(errors::StabilityPromotable { attr_span: attr.span });
1914                 false
1915             }
1916             _ => true,
1917         }
1918     }
1919
1920     fn check_link_ordinal(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
1921         match target {
1922             Target::ForeignFn | Target::ForeignStatic => true,
1923             _ => {
1924                 self.tcx.sess.emit_err(errors::LinkOrdinal { attr_span: attr.span });
1925                 false
1926             }
1927         }
1928     }
1929
1930     fn check_deprecated(&self, hir_id: HirId, attr: &Attribute, _span: Span, target: Target) {
1931         match target {
1932             Target::Closure | Target::Expression | Target::Statement | Target::Arm => {
1933                 self.tcx.emit_spanned_lint(
1934                     UNUSED_ATTRIBUTES,
1935                     hir_id,
1936                     attr.span,
1937                     errors::Deprecated,
1938                 );
1939             }
1940             _ => {}
1941         }
1942     }
1943
1944     fn check_macro_use(&self, hir_id: HirId, attr: &Attribute, target: Target) {
1945         let name = attr.name_or_empty();
1946         match target {
1947             Target::ExternCrate | Target::Mod => {}
1948             _ => {
1949                 self.tcx.emit_spanned_lint(
1950                     UNUSED_ATTRIBUTES,
1951                     hir_id,
1952                     attr.span,
1953                     errors::MacroUse { name },
1954                 );
1955             }
1956         }
1957     }
1958
1959     fn check_macro_export(&self, hir_id: HirId, attr: &Attribute, target: Target) {
1960         if target != Target::MacroDef {
1961             self.tcx.emit_spanned_lint(UNUSED_ATTRIBUTES, hir_id, attr.span, errors::MacroExport);
1962         }
1963     }
1964
1965     fn check_plugin_registrar(&self, hir_id: HirId, attr: &Attribute, target: Target) {
1966         if target != Target::Fn {
1967             self.tcx.emit_spanned_lint(
1968                 UNUSED_ATTRIBUTES,
1969                 hir_id,
1970                 attr.span,
1971                 errors::PluginRegistrar,
1972             );
1973         }
1974     }
1975
1976     fn check_unused_attribute(&self, hir_id: HirId, attr: &Attribute) {
1977         // Warn on useless empty attributes.
1978         let note = if matches!(
1979             attr.name_or_empty(),
1980             sym::macro_use
1981                 | sym::allow
1982                 | sym::expect
1983                 | sym::warn
1984                 | sym::deny
1985                 | sym::forbid
1986                 | sym::feature
1987                 | sym::repr
1988                 | sym::target_feature
1989         ) && attr.meta_item_list().map_or(false, |list| list.is_empty())
1990         {
1991             errors::UnusedNote::EmptyList { name: attr.name_or_empty() }
1992         } else if matches!(
1993                 attr.name_or_empty(),
1994                 sym::allow | sym::warn | sym::deny | sym::forbid | sym::expect
1995             ) && let Some(meta) = attr.meta_item_list()
1996             && meta.len() == 1
1997             && let Some(item) = meta[0].meta_item()
1998             && let MetaItemKind::NameValue(_) = &item.kind
1999             && item.path == sym::reason
2000         {
2001             errors::UnusedNote::NoLints { name: attr.name_or_empty() }
2002         } else if attr.name_or_empty() == sym::default_method_body_is_const {
2003             errors::UnusedNote::DefaultMethodBodyConst
2004         } else {
2005             return;
2006         };
2007
2008         self.tcx.emit_spanned_lint(
2009             UNUSED_ATTRIBUTES,
2010             hir_id,
2011             attr.span,
2012             errors::Unused { attr_span: attr.span, note },
2013         );
2014     }
2015 }
2016
2017 impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
2018     type NestedFilter = nested_filter::OnlyBodies;
2019
2020     fn nested_visit_map(&mut self) -> Self::Map {
2021         self.tcx.hir()
2022     }
2023
2024     fn visit_item(&mut self, item: &'tcx Item<'tcx>) {
2025         // Historically we've run more checks on non-exported than exported macros,
2026         // so this lets us continue to run them while maintaining backwards compatibility.
2027         // In the long run, the checks should be harmonized.
2028         if let ItemKind::Macro(ref macro_def, _) = item.kind {
2029             let def_id = item.def_id.to_def_id();
2030             if macro_def.macro_rules && !self.tcx.has_attr(def_id, sym::macro_export) {
2031                 check_non_exported_macro_for_invalid_attrs(self.tcx, item);
2032             }
2033         }
2034
2035         let target = Target::from_item(item);
2036         self.check_attributes(item.hir_id(), item.span, target, Some(ItemLike::Item(item)));
2037         intravisit::walk_item(self, item)
2038     }
2039
2040     fn visit_generic_param(&mut self, generic_param: &'tcx hir::GenericParam<'tcx>) {
2041         let target = Target::from_generic_param(generic_param);
2042         self.check_attributes(generic_param.hir_id, generic_param.span, target, None);
2043         intravisit::walk_generic_param(self, generic_param)
2044     }
2045
2046     fn visit_trait_item(&mut self, trait_item: &'tcx TraitItem<'tcx>) {
2047         let target = Target::from_trait_item(trait_item);
2048         self.check_attributes(trait_item.hir_id(), trait_item.span, target, None);
2049         intravisit::walk_trait_item(self, trait_item)
2050     }
2051
2052     fn visit_field_def(&mut self, struct_field: &'tcx hir::FieldDef<'tcx>) {
2053         self.check_attributes(struct_field.hir_id, struct_field.span, Target::Field, None);
2054         intravisit::walk_field_def(self, struct_field);
2055     }
2056
2057     fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
2058         self.check_attributes(arm.hir_id, arm.span, Target::Arm, None);
2059         intravisit::walk_arm(self, arm);
2060     }
2061
2062     fn visit_foreign_item(&mut self, f_item: &'tcx ForeignItem<'tcx>) {
2063         let target = Target::from_foreign_item(f_item);
2064         self.check_attributes(f_item.hir_id(), f_item.span, target, Some(ItemLike::ForeignItem));
2065         intravisit::walk_foreign_item(self, f_item)
2066     }
2067
2068     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
2069         let target = target_from_impl_item(self.tcx, impl_item);
2070         self.check_attributes(impl_item.hir_id(), impl_item.span, target, None);
2071         intravisit::walk_impl_item(self, impl_item)
2072     }
2073
2074     fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
2075         // When checking statements ignore expressions, they will be checked later.
2076         if let hir::StmtKind::Local(ref l) = stmt.kind {
2077             self.check_attributes(l.hir_id, stmt.span, Target::Statement, None);
2078         }
2079         intravisit::walk_stmt(self, stmt)
2080     }
2081
2082     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
2083         let target = match expr.kind {
2084             hir::ExprKind::Closure { .. } => Target::Closure,
2085             _ => Target::Expression,
2086         };
2087
2088         self.check_attributes(expr.hir_id, expr.span, target, None);
2089         intravisit::walk_expr(self, expr)
2090     }
2091
2092     fn visit_expr_field(&mut self, field: &'tcx hir::ExprField<'tcx>) {
2093         self.check_attributes(field.hir_id, field.span, Target::ExprField, None);
2094         intravisit::walk_expr_field(self, field)
2095     }
2096
2097     fn visit_variant(&mut self, variant: &'tcx hir::Variant<'tcx>) {
2098         self.check_attributes(variant.id, variant.span, Target::Variant, None);
2099         intravisit::walk_variant(self, variant)
2100     }
2101
2102     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
2103         self.check_attributes(param.hir_id, param.span, Target::Param, None);
2104
2105         intravisit::walk_param(self, param);
2106     }
2107
2108     fn visit_pat_field(&mut self, field: &'tcx hir::PatField<'tcx>) {
2109         self.check_attributes(field.hir_id, field.span, Target::PatField, None);
2110         intravisit::walk_pat_field(self, field);
2111     }
2112 }
2113
2114 fn is_c_like_enum(item: &Item<'_>) -> bool {
2115     if let ItemKind::Enum(ref def, _) = item.kind {
2116         for variant in def.variants {
2117             match variant.data {
2118                 hir::VariantData::Unit(..) => { /* continue */ }
2119                 _ => return false,
2120             }
2121         }
2122         true
2123     } else {
2124         false
2125     }
2126 }
2127
2128 // FIXME: Fix "Cannot determine resolution" error and remove built-in macros
2129 // from this check.
2130 fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
2131     // Check for builtin attributes at the crate level
2132     // which were unsuccessfully resolved due to cannot determine
2133     // resolution for the attribute macro error.
2134     const ATTRS_TO_CHECK: &[Symbol] = &[
2135         sym::macro_export,
2136         sym::repr,
2137         sym::path,
2138         sym::automatically_derived,
2139         sym::start,
2140         sym::rustc_main,
2141         sym::unix_sigpipe,
2142         sym::derive,
2143         sym::test,
2144         sym::test_case,
2145         sym::global_allocator,
2146         sym::bench,
2147     ];
2148
2149     for attr in attrs {
2150         // This function should only be called with crate attributes
2151         // which are inner attributes always but lets check to make sure
2152         if attr.style == AttrStyle::Inner {
2153             for attr_to_check in ATTRS_TO_CHECK {
2154                 if attr.has_name(*attr_to_check) {
2155                     let mut err = tcx.sess.struct_span_err(
2156                         attr.span,
2157                         &format!(
2158                             "`{}` attribute cannot be used at crate level",
2159                             attr_to_check.to_ident_string()
2160                         ),
2161                     );
2162                     // Only emit an error with a suggestion if we can create a
2163                     // string out of the attribute span
2164                     if let Ok(src) = tcx.sess.source_map().span_to_snippet(attr.span) {
2165                         let replacement = src.replace("#!", "#");
2166                         err.span_suggestion_verbose(
2167                             attr.span,
2168                             "perhaps you meant to use an outer attribute",
2169                             replacement,
2170                             rustc_errors::Applicability::MachineApplicable,
2171                         );
2172                     }
2173                     err.emit();
2174                 }
2175             }
2176         }
2177     }
2178 }
2179
2180 fn check_non_exported_macro_for_invalid_attrs(tcx: TyCtxt<'_>, item: &Item<'_>) {
2181     let attrs = tcx.hir().attrs(item.hir_id());
2182
2183     for attr in attrs {
2184         if attr.has_name(sym::inline) {
2185             tcx.sess.emit_err(errors::NonExportedMacroInvalidAttrs { attr_span: attr.span });
2186         }
2187     }
2188 }
2189
2190 fn check_mod_attrs(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
2191     let check_attr_visitor = &mut CheckAttrVisitor { tcx };
2192     tcx.hir().visit_item_likes_in_module(module_def_id, check_attr_visitor);
2193     if module_def_id.is_top_level_module() {
2194         check_attr_visitor.check_attributes(CRATE_HIR_ID, DUMMY_SP, Target::Mod, None);
2195         check_invalid_crate_level_attr(tcx, tcx.hir().krate_attrs());
2196     }
2197 }
2198
2199 pub(crate) fn provide(providers: &mut Providers) {
2200     *providers = Providers { check_mod_attrs, ..*providers };
2201 }
2202
2203 fn check_duplicates(
2204     tcx: TyCtxt<'_>,
2205     attr: &Attribute,
2206     hir_id: HirId,
2207     duplicates: AttributeDuplicates,
2208     seen: &mut FxHashMap<Symbol, Span>,
2209 ) {
2210     use AttributeDuplicates::*;
2211     if matches!(duplicates, WarnFollowingWordOnly) && !attr.is_word() {
2212         return;
2213     }
2214     match duplicates {
2215         DuplicatesOk => {}
2216         WarnFollowing | FutureWarnFollowing | WarnFollowingWordOnly | FutureWarnPreceding => {
2217             match seen.entry(attr.name_or_empty()) {
2218                 Entry::Occupied(mut entry) => {
2219                     let (this, other) = if matches!(duplicates, FutureWarnPreceding) {
2220                         let to_remove = entry.insert(attr.span);
2221                         (to_remove, attr.span)
2222                     } else {
2223                         (attr.span, *entry.get())
2224                     };
2225                     tcx.emit_spanned_lint(
2226                         UNUSED_ATTRIBUTES,
2227                         hir_id,
2228                         this,
2229                         errors::UnusedDuplicate {
2230                             this,
2231                             other,
2232                             warning: matches!(
2233                                 duplicates,
2234                                 FutureWarnFollowing | FutureWarnPreceding
2235                             )
2236                             .then_some(()),
2237                         },
2238                     );
2239                 }
2240                 Entry::Vacant(entry) => {
2241                     entry.insert(attr.span);
2242                 }
2243             }
2244         }
2245         ErrorFollowing | ErrorPreceding => match seen.entry(attr.name_or_empty()) {
2246             Entry::Occupied(mut entry) => {
2247                 let (this, other) = if matches!(duplicates, ErrorPreceding) {
2248                     let to_remove = entry.insert(attr.span);
2249                     (to_remove, attr.span)
2250                 } else {
2251                     (attr.span, *entry.get())
2252                 };
2253                 tcx.sess.emit_err(errors::UnusedMultiple {
2254                     this,
2255                     other,
2256                     name: attr.name_or_empty(),
2257                 });
2258             }
2259             Entry::Vacant(entry) => {
2260                 entry.insert(attr.span);
2261             }
2262         },
2263     }
2264 }