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     self, AttrApplication, DebugVisualizerUnreadable, InvalidAttrAtCrateLevel, ObjectLifetimeErr,
   9     OnlyHasEffectOn, ProcMacroDiffArguments, ProcMacroInvalidAbi, ProcMacroMissingArguments,
  10     ProcMacroTypeError, ProcMacroUnsafe, TransparentIncompatible, UnrecognizedReprHint,
  11 };
  12 use rustc_ast::{ast, AttrStyle, Attribute, LitKind, MetaItemKind, MetaItemLit, NestedMetaItem};
  13 use rustc_data_structures::fx::FxHashMap;
  14 use rustc_errors::{fluent, Applicability, IntoDiagnosticArg, MultiSpan};
  15 use rustc_expand::base::resolve_path;
  16 use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
  17 use rustc_hir as hir;
  18 use rustc_hir::def_id::LocalDefId;
  19 use rustc_hir::intravisit::{self, Visitor};
  20 use rustc_hir::{
  21     self, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID, CRATE_OWNER_ID,
  22 };
  23 use rustc_hir::{MethodKind, Target, Unsafety};
  24 use rustc_middle::hir::nested_filter;
  25 use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
  26 use rustc_middle::ty::query::Providers;
  27 use rustc_middle::ty::{ParamEnv, TyCtxt};
  28 use rustc_session::lint::builtin::{
  29     CONFLICTING_REPR_HINTS, INVALID_DOC_ATTRIBUTES, UNUSED_ATTRIBUTES,
  30 };
  31 use rustc_session::parse::feature_err;
  32 use rustc_span::symbol::{kw, sym, Symbol};
  33 use rustc_span::{Span, DUMMY_SP};
  34 use rustc_target::spec::abi::Abi;
  35 use std::cell::Cell;
  36 use std::collections::hash_map::Entry;
  37
  38 pub(crate) fn target_from_impl_item<'tcx>(
  39     tcx: TyCtxt<'tcx>,
  40     impl_item: &hir::ImplItem<'_>,
  41 ) -> Target {
  42     match impl_item.kind {
  43         hir::ImplItemKind::Const(..) => Target::AssocConst,
  44         hir::ImplItemKind::Fn(..) => {
  45             let parent_def_id = tcx.hir().get_parent_item(impl_item.hir_id()).def_id;
  46             let containing_item = tcx.hir().expect_item(parent_def_id);
  47             let containing_impl_is_for_trait = match &containing_item.kind {
  48                 hir::ItemKind::Impl(impl_) => impl_.of_trait.is_some(),
  49                 _ => bug!("parent of an ImplItem must be an Impl"),
  50             };
  51             if containing_impl_is_for_trait {
  52                 Target::Method(MethodKind::Trait { body: true })
  53             } else {
  54                 Target::Method(MethodKind::Inherent)
  55             }
  56         }
  57         hir::ImplItemKind::Type(..) => Target::AssocTy,
  58     }
  59 }
  60
  61 #[derive(Clone, Copy)]
  62 enum ItemLike<'tcx> {
  63     Item(&'tcx Item<'tcx>),
  64     ForeignItem,
  65 }
  66
  67 #[derive(Copy, Clone)]
  68 pub(crate) enum ProcMacroKind {
  69     FunctionLike,
  70     Derive,
  71     Attribute,
  72 }
  73
  74 impl IntoDiagnosticArg for ProcMacroKind {
  75     fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
  76         match self {
  77             ProcMacroKind::Attribute => "attribute proc macro",
  78             ProcMacroKind::Derive => "derive proc macro",
  79             ProcMacroKind::FunctionLike => "function-like proc macro",
  80         }
  81         .into_diagnostic_arg()
  82     }
  83 }
  84
  85 struct CheckAttrVisitor<'tcx> {
  86     tcx: TyCtxt<'tcx>,
  87     abort: Cell<bool>,
  88 }
  89
  90 impl CheckAttrVisitor<'_> {
  91     /// Checks any attribute.
  92     fn check_attributes(
  93         &self,
  94         hir_id: HirId,
  95         span: Span,
  96         target: Target,
  97         item: Option<ItemLike<'_>>,
  98     ) {
  99         let mut doc_aliases = FxHashMap::default();
 100         let mut is_valid = true;
 101         let mut specified_inline = None;
 102         let mut seen = FxHashMap::default();
 103         let attrs = self.tcx.hir().attrs(hir_id);
 104         for attr in attrs {
 105             let attr_is_valid = match attr.name_or_empty() {
 106                 sym::inline => self.check_inline(hir_id, attr, span, target),
 107                 sym::no_coverage => self.check_no_coverage(hir_id, attr, span, target),
 108                 sym::non_exhaustive => self.check_non_exhaustive(hir_id, attr, span, target),
 109                 sym::marker => self.check_marker(hir_id, attr, span, target),
 110                 sym::rustc_must_implement_one_of => {
 111                     self.check_rustc_must_implement_one_of(attr, span, target)
 112                 }
 113                 sym::target_feature => self.check_target_feature(hir_id, attr, span, target),
 114                 sym::thread_local => self.check_thread_local(attr, span, target),
 115                 sym::track_caller => {
 116                     self.check_track_caller(hir_id, attr.span, attrs, span, target)
 117                 }
 118                 sym::doc => self.check_doc_attrs(
 119                     attr,
 120                     hir_id,
 121                     target,
 122                     &mut specified_inline,
 123                     &mut doc_aliases,
 124                 ),
 125                 sym::no_link => self.check_no_link(hir_id, &attr, span, target),
 126                 sym::export_name => self.check_export_name(hir_id, &attr, span, target),
 127                 sym::rustc_layout_scalar_valid_range_start
 128                 | sym::rustc_layout_scalar_valid_range_end => {
 129                     self.check_rustc_layout_scalar_valid_range(&attr, span, target)
 130                 }
 131                 sym::allow_internal_unstable => {
 132                     self.check_allow_internal_unstable(hir_id, &attr, span, target, &attrs)
 133                 }
 134                 sym::debugger_visualizer => self.check_debugger_visualizer(&attr, target),
 135                 sym::rustc_allow_const_fn_unstable => {
 136                     self.check_rustc_allow_const_fn_unstable(hir_id, &attr, span, target)
 137                 }
 138                 sym::rustc_std_internal_symbol => {
 139                     self.check_rustc_std_internal_symbol(&attr, span, target)
 140                 }
 141                 sym::naked => self.check_naked(hir_id, attr, span, target),
 142                 sym::rustc_legacy_const_generics => {
 143                     self.check_rustc_legacy_const_generics(hir_id, &attr, span, target, item)
 144                 }
 145                 sym::rustc_lint_query_instability => {
 146                     self.check_rustc_lint_query_instability(hir_id, &attr, span, target)
 147                 }
 148                 sym::rustc_lint_diagnostics => {
 149                     self.check_rustc_lint_diagnostics(hir_id, &attr, span, target)
 150                 }
 151                 sym::rustc_lint_opt_ty => self.check_rustc_lint_opt_ty(&attr, span, target),
 152                 sym::rustc_lint_opt_deny_field_access => {
 153                     self.check_rustc_lint_opt_deny_field_access(&attr, span, target)
 154                 }
 155                 sym::rustc_clean
 156                 | sym::rustc_dirty
 157                 | sym::rustc_if_this_changed
 158                 | sym::rustc_then_this_would_need => self.check_rustc_dirty_clean(&attr),
 159                 sym::cmse_nonsecure_entry => {
 160                     self.check_cmse_nonsecure_entry(hir_id, attr, span, target)
 161                 }
 162                 sym::collapse_debuginfo => self.check_collapse_debuginfo(attr, span, target),
 163                 sym::const_trait => self.check_const_trait(attr, span, target),
 164                 sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target),
 165                 sym::must_use => self.check_must_use(hir_id, &attr, target),
 166                 sym::rustc_pass_by_value => self.check_pass_by_value(&attr, span, target),
 167                 sym::rustc_allow_incoherent_impl => {
 168                     self.check_allow_incoherent_impl(&attr, span, target)
 169                 }
 170                 sym::rustc_has_incoherent_inherent_impls => {
 171                     self.check_has_incoherent_inherent_impls(&attr, span, target)
 172                 }
 173                 sym::rustc_const_unstable
 174                 | sym::rustc_const_stable
 175                 | sym::unstable
 176                 | sym::stable
 177                 | sym::rustc_allowed_through_unstable_modules
 178                 | sym::rustc_promotable => self.check_stability_promotable(&attr, span, target),
 179                 sym::link_ordinal => self.check_link_ordinal(&attr, span, target),
 180                 _ => true,
 181             };
 182             is_valid &= attr_is_valid;
 183
 184             // lint-only checks
 185             match attr.name_or_empty() {
 186                 sym::cold => self.check_cold(hir_id, attr, span, target),
 187                 sym::link => self.check_link(hir_id, attr, span, target),
 188                 sym::link_name => self.check_link_name(hir_id, attr, span, target),
 189                 sym::link_section => self.check_link_section(hir_id, attr, span, target),
 190                 sym::no_mangle => self.check_no_mangle(hir_id, attr, span, target),
 191                 sym::deprecated => self.check_deprecated(hir_id, attr, span, target),
 192                 sym::macro_use | sym::macro_escape => self.check_macro_use(hir_id, attr, target),
 193                 sym::path => self.check_generic_attr(hir_id, attr, target, Target::Mod),
 194                 sym::plugin_registrar => self.check_plugin_registrar(hir_id, attr, target),
 195                 sym::macro_export => self.check_macro_export(hir_id, attr, target),
 196                 sym::ignore | sym::should_panic => {
 197                     self.check_generic_attr(hir_id, attr, target, Target::Fn)
 198                 }
 199                 sym::automatically_derived => {
 200                     self.check_generic_attr(hir_id, attr, target, Target::Impl)
 201                 }
 202                 sym::no_implicit_prelude => {
 203                     self.check_generic_attr(hir_id, attr, target, Target::Mod)
 204                 }
 205                 sym::rustc_object_lifetime_default => self.check_object_lifetime_default(hir_id),
 206                 sym::proc_macro => {
 207                     self.check_proc_macro(hir_id, target, ProcMacroKind::FunctionLike)
 208                 }
 209                 sym::proc_macro_attribute => {
 210                     self.check_proc_macro(hir_id, target, ProcMacroKind::Attribute);
 211                 }
 212                 sym::proc_macro_derive => {
 213                     self.check_generic_attr(hir_id, attr, target, Target::Fn);
 214                     self.check_proc_macro(hir_id, target, ProcMacroKind::Derive)
 215                 }
 216                 _ => {}
 217             }
 218
 219             let builtin = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
 220
 221             if hir_id != CRATE_HIR_ID {
 222                 if let Some(BuiltinAttribute { type_: AttributeType::CrateLevel, .. }) =
 223                     attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name))
 224                 {
 225                     match attr.style {
 226                         ast::AttrStyle::Outer => self.tcx.emit_spanned_lint(
 227                             UNUSED_ATTRIBUTES,
 228                             hir_id,
 229                             attr.span,
 230                             errors::OuterCrateLevelAttr,
 231                         ),
 232                         ast::AttrStyle::Inner => self.tcx.emit_spanned_lint(
 233                             UNUSED_ATTRIBUTES,
 234                             hir_id,
 235                             attr.span,
 236                             errors::InnerCrateLevelAttr,
 237                         ),
 238                     }
 239                 }
 240             }
 241
 242             if let Some(BuiltinAttribute { duplicates, .. }) = builtin {
 243                 check_duplicates(self.tcx, attr, hir_id, *duplicates, &mut seen);
 244             }
 245
 246             self.check_unused_attribute(hir_id, attr)
 247         }
 248
 249         if !is_valid {
 250             return;
 251         }
 252
 253         self.check_repr(attrs, span, target, item, hir_id);
 254         self.check_used(attrs, target);
 255     }
 256
 257     fn inline_attr_str_error_with_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
 258         self.tcx.emit_spanned_lint(
 259             UNUSED_ATTRIBUTES,
 260             hir_id,
 261             attr.span,
 262             errors::IgnoredAttrWithMacro { sym },
 263         );
 264     }
 265
 266     fn inline_attr_str_error_without_macro_def(&self, hir_id: HirId, attr: &Attribute, sym: &str) {
 267         self.tcx.emit_spanned_lint(
 268             UNUSED_ATTRIBUTES,
 269             hir_id,
 270             attr.span,
 271             errors::IgnoredAttr { sym },
 272         );
 273     }
 274
 275     /// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid.
 276     fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
 277         match target {
 278             Target::Fn
 279             | Target::Closure
 280             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 281             Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
 282                 self.tcx.emit_spanned_lint(
 283                     UNUSED_ATTRIBUTES,
 284                     hir_id,
 285                     attr.span,
 286                     errors::IgnoredInlineAttrFnProto,
 287                 );
 288                 true
 289             }
 290             // FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with
 291             // just a lint, because we previously erroneously allowed it and some crates used it
 292             // accidentally, to be compatible with crates depending on them, we can't throw an
 293             // error here.
 294             Target::AssocConst => {
 295                 self.tcx.emit_spanned_lint(
 296                     UNUSED_ATTRIBUTES,
 297                     hir_id,
 298                     attr.span,
 299                     errors::IgnoredInlineAttrConstants,
 300                 );
 301                 true
 302             }
 303             // FIXME(#80564): Same for fields, arms, and macro defs
 304             Target::Field | Target::Arm | Target::MacroDef => {
 305                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "inline");
 306                 true
 307             }
 308             _ => {
 309                 self.tcx.sess.emit_err(errors::InlineNotFnOrClosure {
 310                     attr_span: attr.span,
 311                     defn_span: span,
 312                 });
 313                 false
 314             }
 315         }
 316     }
 317
 318     /// Checks if a `#[no_coverage]` is applied directly to a function
 319     fn check_no_coverage(
 320         &self,
 321         hir_id: HirId,
 322         attr: &Attribute,
 323         span: Span,
 324         target: Target,
 325     ) -> bool {
 326         match target {
 327             // no_coverage on function is fine
 328             Target::Fn
 329             | Target::Closure
 330             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 331
 332             // function prototypes can't be covered
 333             Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
 334                 self.tcx.emit_spanned_lint(
 335                     UNUSED_ATTRIBUTES,
 336                     hir_id,
 337                     attr.span,
 338                     errors::IgnoredNoCoverageFnProto,
 339                 );
 340                 true
 341             }
 342
 343             Target::Mod | Target::ForeignMod | Target::Impl | Target::Trait => {
 344                 self.tcx.emit_spanned_lint(
 345                     UNUSED_ATTRIBUTES,
 346                     hir_id,
 347                     attr.span,
 348                     errors::IgnoredNoCoveragePropagate,
 349                 );
 350                 true
 351             }
 352
 353             Target::Expression | Target::Statement | Target::Arm => {
 354                 self.tcx.emit_spanned_lint(
 355                     UNUSED_ATTRIBUTES,
 356                     hir_id,
 357                     attr.span,
 358                     errors::IgnoredNoCoverageFnDefn,
 359                 );
 360                 true
 361             }
 362
 363             _ => {
 364                 self.tcx.sess.emit_err(errors::IgnoredNoCoverageNotCoverable {
 365                     attr_span: attr.span,
 366                     defn_span: span,
 367                 });
 368                 false
 369             }
 370         }
 371     }
 372
 373     fn check_generic_attr(
 374         &self,
 375         hir_id: HirId,
 376         attr: &Attribute,
 377         target: Target,
 378         allowed_target: Target,
 379     ) {
 380         if target != allowed_target {
 381             self.tcx.emit_spanned_lint(
 382                 UNUSED_ATTRIBUTES,
 383                 hir_id,
 384                 attr.span,
 385                 OnlyHasEffectOn {
 386                     attr_name: attr.name_or_empty(),
 387                     target_name: allowed_target.name().replace(' ', "_"),
 388                 },
 389             );
 390         }
 391     }
 392
 393     /// Checks if `#[naked]` is applied to a function definition.
 394     fn check_naked(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
 395         match target {
 396             Target::Fn
 397             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 398             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 399             // `#[allow_internal_unstable]` attribute with just a lint, because we previously
 400             // erroneously allowed it and some crates used it accidentally, to be compatible
 401             // with crates depending on them, we can't throw an error here.
 402             Target::Field | Target::Arm | Target::MacroDef => {
 403                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "naked");
 404                 true
 405             }
 406             _ => {
 407                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
 408                     attr_span: attr.span,
 409                     defn_span: span,
 410                     on_crate: hir_id == CRATE_HIR_ID,
 411                 });
 412                 false
 413             }
 414         }
 415     }
 416
 417     /// Checks if `#[cmse_nonsecure_entry]` is applied to a function definition.
 418     fn check_cmse_nonsecure_entry(
 419         &self,
 420         hir_id: HirId,
 421         attr: &Attribute,
 422         span: Span,
 423         target: Target,
 424     ) -> bool {
 425         match target {
 426             Target::Fn
 427             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 428             _ => {
 429                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
 430                     attr_span: attr.span,
 431                     defn_span: span,
 432                     on_crate: hir_id == CRATE_HIR_ID,
 433                 });
 434                 false
 435             }
 436         }
 437     }
 438
 439     /// Debugging aid for `object_lifetime_default` query.
 440     fn check_object_lifetime_default(&self, hir_id: HirId) {
 441         let tcx = self.tcx;
 442         if let Some(generics) = tcx.hir().get_generics(tcx.hir().local_def_id(hir_id)) {
 443             for p in generics.params {
 444                 let hir::GenericParamKind::Type { .. } = p.kind else { continue };
 445                 let default = tcx.object_lifetime_default(p.def_id);
 446                 let repr = match default {
 447                     ObjectLifetimeDefault::Empty => "BaseDefault".to_owned(),
 448                     ObjectLifetimeDefault::Static => "'static".to_owned(),
 449                     ObjectLifetimeDefault::Param(def_id) => tcx.item_name(def_id).to_string(),
 450                     ObjectLifetimeDefault::Ambiguous => "Ambiguous".to_owned(),
 451                 };
 452                 tcx.sess.emit_err(ObjectLifetimeErr { span: p.span, repr });
 453             }
 454         }
 455     }
 456
 457     /// Checks if `#[collapse_debuginfo]` is applied to a macro.
 458     fn check_collapse_debuginfo(&self, attr: &Attribute, span: Span, target: Target) -> bool {
 459         match target {
 460             Target::MacroDef => true,
 461             _ => {
 462                 self.tcx
 463                     .sess
 464                     .emit_err(errors::CollapseDebuginfo { attr_span: attr.span, defn_span: span });
 465                 false
 466             }
 467         }
 468     }
 469
 470     /// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid.
 471     fn check_track_caller(
 472         &self,
 473         hir_id: HirId,
 474         attr_span: Span,
 475         attrs: &[Attribute],
 476         span: Span,
 477         target: Target,
 478     ) -> bool {
 479         match target {
 480             _ if attrs.iter().any(|attr| attr.has_name(sym::naked)) => {
 481                 self.tcx.sess.emit_err(errors::NakedTrackedCaller { attr_span });
 482                 false
 483             }
 484             Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => true,
 485             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 486             // `#[track_caller]` attribute with just a lint, because we previously
 487             // erroneously allowed it and some crates used it accidentally, to be compatible
 488             // with crates depending on them, we can't throw an error here.
 489             Target::Field | Target::Arm | Target::MacroDef => {
 490                 for attr in attrs {
 491                     self.inline_attr_str_error_with_macro_def(hir_id, attr, "track_caller");
 492                 }
 493                 true
 494             }
 495             _ => {
 496                 self.tcx.sess.emit_err(errors::TrackedCallerWrongLocation {
 497                     attr_span,
 498                     defn_span: span,
 499                     on_crate: hir_id == CRATE_HIR_ID,
 500                 });
 501                 false
 502             }
 503         }
 504     }
 505
 506     /// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid.
 507     fn check_non_exhaustive(
 508         &self,
 509         hir_id: HirId,
 510         attr: &Attribute,
 511         span: Span,
 512         target: Target,
 513     ) -> bool {
 514         match target {
 515             Target::Struct | Target::Enum | Target::Variant => true,
 516             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 517             // `#[non_exhaustive]` attribute with just a lint, because we previously
 518             // erroneously allowed it and some crates used it accidentally, to be compatible
 519             // with crates depending on them, we can't throw an error here.
 520             Target::Field | Target::Arm | Target::MacroDef => {
 521                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "non_exhaustive");
 522                 true
 523             }
 524             _ => {
 525                 self.tcx.sess.emit_err(errors::NonExhaustiveWrongLocation {
 526                     attr_span: attr.span,
 527                     defn_span: span,
 528                 });
 529                 false
 530             }
 531         }
 532     }
 533
 534     /// Checks if the `#[marker]` attribute on an `item` is valid. Returns `true` if valid.
 535     fn check_marker(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
 536         match target {
 537             Target::Trait => true,
 538             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 539             // `#[marker]` attribute with just a lint, because we previously
 540             // erroneously allowed it and some crates used it accidentally, to be compatible
 541             // with crates depending on them, we can't throw an error here.
 542             Target::Field | Target::Arm | Target::MacroDef => {
 543                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "marker");
 544                 true
 545             }
 546             _ => {
 547                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
 548                     attr_span: attr.span,
 549                     defn_span: span,
 550                 });
 551                 false
 552             }
 553         }
 554     }
 555
 556     /// Checks if the `#[rustc_must_implement_one_of]` attribute on a `target` is valid. Returns `true` if valid.
 557     fn check_rustc_must_implement_one_of(
 558         &self,
 559         attr: &Attribute,
 560         span: Span,
 561         target: Target,
 562     ) -> bool {
 563         match target {
 564             Target::Trait => true,
 565             _ => {
 566                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
 567                     attr_span: attr.span,
 568                     defn_span: span,
 569                 });
 570                 false
 571             }
 572         }
 573     }
 574
 575     /// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid.
 576     fn check_target_feature(
 577         &self,
 578         hir_id: HirId,
 579         attr: &Attribute,
 580         span: Span,
 581         target: Target,
 582     ) -> bool {
 583         match target {
 584             Target::Fn
 585             | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
 586             // FIXME: #[target_feature] was previously erroneously allowed on statements and some
 587             // crates used this, so only emit a warning.
 588             Target::Statement => {
 589                 self.tcx.emit_spanned_lint(
 590                     UNUSED_ATTRIBUTES,
 591                     hir_id,
 592                     attr.span,
 593                     errors::TargetFeatureOnStatement,
 594                 );
 595                 true
 596             }
 597             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
 598             // `#[target_feature]` attribute with just a lint, because we previously
 599             // erroneously allowed it and some crates used it accidentally, to be compatible
 600             // with crates depending on them, we can't throw an error here.
 601             Target::Field | Target::Arm | Target::MacroDef => {
 602                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "target_feature");
 603                 true
 604             }
 605             _ => {
 606                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
 607                     attr_span: attr.span,
 608                     defn_span: span,
 609                     on_crate: hir_id == CRATE_HIR_ID,
 610                 });
 611                 false
 612             }
 613         }
 614     }
 615
 616     /// Checks if the `#[thread_local]` attribute on `item` is valid. Returns `true` if valid.
 617     fn check_thread_local(&self, attr: &Attribute, span: Span, target: Target) -> bool {
 618         match target {
 619             Target::ForeignStatic | Target::Static => true,
 620             _ => {
 621                 self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToStatic {
 622                     attr_span: attr.span,
 623                     defn_span: span,
 624                 });
 625                 false
 626             }
 627         }
 628     }
 629
 630     fn doc_attr_str_error(&self, meta: &NestedMetaItem, attr_name: &str) {
 631         self.tcx.sess.emit_err(errors::DocExpectStr { attr_span: meta.span(), attr_name });
 632     }
 633
 634     fn check_doc_alias_value(
 635         &self,
 636         meta: &NestedMetaItem,
 637         doc_alias: Symbol,
 638         hir_id: HirId,
 639         target: Target,
 640         is_list: bool,
 641         aliases: &mut FxHashMap<String, Span>,
 642     ) -> bool {
 643         let tcx = self.tcx;
 644         let span = meta.name_value_literal_span().unwrap_or_else(|| meta.span());
 645         let attr_str =
 646             &format!("`#[doc(alias{})]`", if is_list { "(\"...\")" } else { " = \"...\"" });
 647         if doc_alias == kw::Empty {
 648             tcx.sess.emit_err(errors::DocAliasEmpty { span, attr_str });
 649             return false;
 650         }
 651
 652         let doc_alias_str = doc_alias.as_str();
 653         if let Some(c) = doc_alias_str
 654             .chars()
 655             .find(|&c| c == '"' || c == '\'' || (c.is_whitespace() && c != ' '))
 656         {
 657             tcx.sess.emit_err(errors::DocAliasBadChar { span, attr_str, char_: c });
 658             return false;
 659         }
 660         if doc_alias_str.starts_with(' ') || doc_alias_str.ends_with(' ') {
 661             tcx.sess.emit_err(errors::DocAliasStartEnd { span, attr_str });
 662             return false;
 663         }
 664
 665         let span = meta.span();
 666         if let Some(location) = match target {
 667             Target::AssocTy => {
 668                 let parent_def_id = self.tcx.hir().get_parent_item(hir_id).def_id;
 669                 let containing_item = self.tcx.hir().expect_item(parent_def_id);
 670                 if Target::from_item(containing_item) == Target::Impl {
 671                     Some("type alias in implementation block")
 672                 } else {
 673                     None
 674                 }
 675             }
 676             Target::AssocConst => {
 677                 let parent_def_id = self.tcx.hir().get_parent_item(hir_id).def_id;
 678                 let containing_item = self.tcx.hir().expect_item(parent_def_id);
 679                 // We can't link to trait impl's consts.
 680                 let err = "associated constant in trait implementation block";
 681                 match containing_item.kind {
 682                     ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) => Some(err),
 683                     _ => None,
 684                 }
 685             }
 686             // we check the validity of params elsewhere
 687             Target::Param => return false,
 688             Target::Expression
 689             | Target::Statement
 690             | Target::Arm
 691             | Target::ForeignMod
 692             | Target::Closure
 693             | Target::Impl => Some(target.name()),
 694             Target::ExternCrate
 695             | Target::Use
 696             | Target::Static
 697             | Target::Const
 698             | Target::Fn
 699             | Target::Mod
 700             | Target::GlobalAsm
 701             | Target::TyAlias
 702             | Target::OpaqueTy
 703             | Target::ImplTraitPlaceholder
 704             | Target::Enum
 705             | Target::Variant
 706             | Target::Struct
 707             | Target::Field
 708             | Target::Union
 709             | Target::Trait
 710             | Target::TraitAlias
 711             | Target::Method(..)
 712             | Target::ForeignFn
 713             | Target::ForeignStatic
 714             | Target::ForeignTy
 715             | Target::GenericParam(..)
 716             | Target::MacroDef
 717             | Target::PatField
 718             | Target::ExprField => None,
 719         } {
 720             tcx.sess.emit_err(errors::DocAliasBadLocation { span, attr_str, location });
 721             return false;
 722         }
 723         let item_name = self.tcx.hir().name(hir_id);
 724         if item_name == doc_alias {
 725             tcx.sess.emit_err(errors::DocAliasNotAnAlias { span, attr_str });
 726             return false;
 727         }
 728         if let Err(entry) = aliases.try_insert(doc_alias_str.to_owned(), span) {
 729             self.tcx.emit_spanned_lint(
 730                 UNUSED_ATTRIBUTES,
 731                 hir_id,
 732                 span,
 733                 errors::DocAliasDuplicated { first_defn: *entry.entry.get() },
 734             );
 735         }
 736         true
 737     }
 738
 739     fn check_doc_alias(
 740         &self,
 741         meta: &NestedMetaItem,
 742         hir_id: HirId,
 743         target: Target,
 744         aliases: &mut FxHashMap<String, Span>,
 745     ) -> bool {
 746         if let Some(values) = meta.meta_item_list() {
 747             let mut errors = 0;
 748             for v in values {
 749                 match v.lit() {
 750                     Some(l) => match l.kind {
 751                         LitKind::Str(s, _) => {
 752                             if !self.check_doc_alias_value(v, s, hir_id, target, true, aliases) {
 753                                 errors += 1;
 754                             }
 755                         }
 756                         _ => {
 757                             self.tcx
 758                                 .sess
 759                                 .emit_err(errors::DocAliasNotStringLiteral { span: v.span() });
 760                             errors += 1;
 761                         }
 762                     },
 763                     None => {
 764                         self.tcx.sess.emit_err(errors::DocAliasNotStringLiteral { span: v.span() });
 765                         errors += 1;
 766                     }
 767                 }
 768             }
 769             errors == 0
 770         } else if let Some(doc_alias) = meta.value_str() {
 771             self.check_doc_alias_value(meta, doc_alias, hir_id, target, false, aliases)
 772         } else {
 773             self.tcx.sess.emit_err(errors::DocAliasMalformed { span: meta.span() });
 774             false
 775         }
 776     }
 777
 778     fn check_doc_keyword(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 779         let doc_keyword = meta.value_str().unwrap_or(kw::Empty);
 780         if doc_keyword == kw::Empty {
 781             self.doc_attr_str_error(meta, "keyword");
 782             return false;
 783         }
 784         match self.tcx.hir().find(hir_id).and_then(|node| match node {
 785             hir::Node::Item(item) => Some(&item.kind),
 786             _ => None,
 787         }) {
 788             Some(ItemKind::Mod(ref module)) => {
 789                 if !module.item_ids.is_empty() {
 790                     self.tcx.sess.emit_err(errors::DocKeywordEmptyMod { span: meta.span() });
 791                     return false;
 792                 }
 793             }
 794             _ => {
 795                 self.tcx.sess.emit_err(errors::DocKeywordNotMod { span: meta.span() });
 796                 return false;
 797             }
 798         }
 799         if !rustc_lexer::is_ident(doc_keyword.as_str()) {
 800             self.tcx.sess.emit_err(errors::DocKeywordInvalidIdent {
 801                 span: meta.name_value_literal_span().unwrap_or_else(|| meta.span()),
 802                 doc_keyword,
 803             });
 804             return false;
 805         }
 806         true
 807     }
 808
 809     fn check_doc_fake_variadic(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 810         match self.tcx.hir().find(hir_id).and_then(|node| match node {
 811             hir::Node::Item(item) => Some(&item.kind),
 812             _ => None,
 813         }) {
 814             Some(ItemKind::Impl(ref i)) => {
 815                 let is_valid = matches!(&i.self_ty.kind, hir::TyKind::Tup([_]))
 816                     || if let hir::TyKind::BareFn(bare_fn_ty) = &i.self_ty.kind {
 817                         bare_fn_ty.decl.inputs.len() == 1
 818                     } else {
 819                         false
 820                     };
 821                 if !is_valid {
 822                     self.tcx.sess.emit_err(errors::DocFakeVariadicNotValid { span: meta.span() });
 823                     return false;
 824                 }
 825             }
 826             _ => {
 827                 self.tcx.sess.emit_err(errors::DocKeywordOnlyImpl { span: meta.span() });
 828                 return false;
 829             }
 830         }
 831         true
 832     }
 833
 834     /// Checks `#[doc(inline)]`/`#[doc(no_inline)]` attributes. Returns `true` if valid.
 835     ///
 836     /// A doc inlining attribute is invalid if it is applied to a non-`use` item, or
 837     /// if there are conflicting attributes for one item.
 838     ///
 839     /// `specified_inline` is used to keep track of whether we have
 840     /// already seen an inlining attribute for this item.
 841     /// If so, `specified_inline` holds the value and the span of
 842     /// the first `inline`/`no_inline` attribute.
 843     fn check_doc_inline(
 844         &self,
 845         attr: &Attribute,
 846         meta: &NestedMetaItem,
 847         hir_id: HirId,
 848         target: Target,
 849         specified_inline: &mut Option<(bool, Span)>,
 850     ) -> bool {
 851         if target == Target::Use || target == Target::ExternCrate {
 852             let do_inline = meta.name_or_empty() == sym::inline;
 853             if let Some((prev_inline, prev_span)) = *specified_inline {
 854                 if do_inline != prev_inline {
 855                     let mut spans = MultiSpan::from_spans(vec![prev_span, meta.span()]);
 856                     spans.push_span_label(prev_span, fluent::passes_doc_inline_conflict_first);
 857                     spans.push_span_label(meta.span(), fluent::passes_doc_inline_conflict_second);
 858                     self.tcx.sess.emit_err(errors::DocKeywordConflict { spans });
 859                     return false;
 860                 }
 861                 true
 862             } else {
 863                 *specified_inline = Some((do_inline, meta.span()));
 864                 true
 865             }
 866         } else {
 867             self.tcx.emit_spanned_lint(
 868                 INVALID_DOC_ATTRIBUTES,
 869                 hir_id,
 870                 meta.span(),
 871                 errors::DocInlineOnlyUse {
 872                     attr_span: meta.span(),
 873                     item_span: (attr.style == AttrStyle::Outer)
 874                         .then(|| self.tcx.hir().span(hir_id)),
 875                 },
 876             );
 877             false
 878         }
 879     }
 880
 881     /// Checks that an attribute is *not* used at the crate level. Returns `true` if valid.
 882     fn check_attr_not_crate_level(
 883         &self,
 884         meta: &NestedMetaItem,
 885         hir_id: HirId,
 886         attr_name: &str,
 887     ) -> bool {
 888         if CRATE_HIR_ID == hir_id {
 889             self.tcx.sess.emit_err(errors::DocAttrNotCrateLevel { span: meta.span(), attr_name });
 890             return false;
 891         }
 892         true
 893     }
 894
 895     /// Checks that an attribute is used at the crate level. Returns `true` if valid.
 896     fn check_attr_crate_level(
 897         &self,
 898         attr: &Attribute,
 899         meta: &NestedMetaItem,
 900         hir_id: HirId,
 901     ) -> bool {
 902         if hir_id != CRATE_HIR_ID {
 903             self.tcx.struct_span_lint_hir(
 904                 INVALID_DOC_ATTRIBUTES,
 905                 hir_id,
 906                 meta.span(),
 907                 fluent::passes_attr_crate_level,
 908                 |err| {
 909                     if attr.style == AttrStyle::Outer
 910                         && self.tcx.hir().get_parent_item(hir_id) == CRATE_OWNER_ID
 911                     {
 912                         if let Ok(mut src) = self.tcx.sess.source_map().span_to_snippet(attr.span) {
 913                             src.insert(1, '!');
 914                             err.span_suggestion_verbose(
 915                                 attr.span,
 916                                 fluent::suggestion,
 917                                 src,
 918                                 Applicability::MaybeIncorrect,
 919                             );
 920                         } else {
 921                             err.span_help(attr.span, fluent::help);
 922                         }
 923                     }
 924                     err.note(fluent::note);
 925                     err
 926                 },
 927             );
 928             return false;
 929         }
 930         true
 931     }
 932
 933     /// Checks that `doc(test(...))` attribute contains only valid attributes. Returns `true` if
 934     /// valid.
 935     fn check_test_attr(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 936         let mut is_valid = true;
 937         if let Some(metas) = meta.meta_item_list() {
 938             for i_meta in metas {
 939                 match i_meta.name_or_empty() {
 940                     sym::attr | sym::no_crate_inject => {}
 941                     _ => {
 942                         self.tcx.emit_spanned_lint(
 943                             INVALID_DOC_ATTRIBUTES,
 944                             hir_id,
 945                             i_meta.span(),
 946                             errors::DocTestUnknown {
 947                                 path: rustc_ast_pretty::pprust::path_to_string(
 948                                     &i_meta.meta_item().unwrap().path,
 949                                 ),
 950                             },
 951                         );
 952                         is_valid = false;
 953                     }
 954                 }
 955             }
 956         } else {
 957             self.tcx.emit_spanned_lint(
 958                 INVALID_DOC_ATTRIBUTES,
 959                 hir_id,
 960                 meta.span(),
 961                 errors::DocTestTakesList,
 962             );
 963             is_valid = false;
 964         }
 965         is_valid
 966     }
 967
 968     /// Check that the `#![doc(cfg_hide(...))]` attribute only contains a list of attributes.
 969     /// Returns `true` if valid.
 970     fn check_doc_cfg_hide(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
 971         if meta.meta_item_list().is_some() {
 972             true
 973         } else {
 974             self.tcx.emit_spanned_lint(
 975                 INVALID_DOC_ATTRIBUTES,
 976                 hir_id,
 977                 meta.span(),
 978                 errors::DocCfgHideTakesList,
 979             );
 980             false
 981         }
 982     }
 983
 984     /// Runs various checks on `#[doc]` attributes. Returns `true` if valid.
 985     ///
 986     /// `specified_inline` should be initialized to `None` and kept for the scope
 987     /// of one item. Read the documentation of [`check_doc_inline`] for more information.
 988     ///
 989     /// [`check_doc_inline`]: Self::check_doc_inline
 990     fn check_doc_attrs(
 991         &self,
 992         attr: &Attribute,
 993         hir_id: HirId,
 994         target: Target,
 995         specified_inline: &mut Option<(bool, Span)>,
 996         aliases: &mut FxHashMap<String, Span>,
 997     ) -> bool {
 998         let mut is_valid = true;
 999
1000         if let Some(mi) = attr.meta() && let Some(list) = mi.meta_item_list() {
1001             for meta in list {
1002                 if let Some(i_meta) = meta.meta_item() {
1003                     match i_meta.name_or_empty() {
1004                         sym::alias
1005                             if !self.check_attr_not_crate_level(meta, hir_id, "alias")
1006                                 || !self.check_doc_alias(meta, hir_id, target, aliases) =>
1007                         {
1008                             is_valid = false
1009                         }
1010
1011                         sym::keyword
1012                             if !self.check_attr_not_crate_level(meta, hir_id, "keyword")
1013                                 || !self.check_doc_keyword(meta, hir_id) =>
1014                         {
1015                             is_valid = false
1016                         }
1017
1018                         sym::fake_variadic
1019                             if !self.check_attr_not_crate_level(meta, hir_id, "fake_variadic")
1020                                 || !self.check_doc_fake_variadic(meta, hir_id) =>
1021                         {
1022                             is_valid = false
1023                         }
1024
1025                         sym::html_favicon_url
1026                         | sym::html_logo_url
1027                         | sym::html_playground_url
1028                         | sym::issue_tracker_base_url
1029                         | sym::html_root_url
1030                         | sym::html_no_source
1031                         | sym::test
1032                             if !self.check_attr_crate_level(attr, meta, hir_id) =>
1033                         {
1034                             is_valid = false;
1035                         }
1036
1037                         sym::cfg_hide
1038                             if !self.check_attr_crate_level(attr, meta, hir_id)
1039                                 || !self.check_doc_cfg_hide(meta, hir_id) =>
1040                         {
1041                             is_valid = false;
1042                         }
1043
1044                         sym::inline | sym::no_inline
1045                             if !self.check_doc_inline(
1046                                 attr,
1047                                 meta,
1048                                 hir_id,
1049                                 target,
1050                                 specified_inline,
1051                             ) =>
1052                         {
1053                             is_valid = false;
1054                         }
1055
1056                         // no_default_passes: deprecated
1057                         // passes: deprecated
1058                         // plugins: removed, but rustdoc warns about it itself
1059                         sym::alias
1060                         | sym::cfg
1061                         | sym::cfg_hide
1062                         | sym::hidden
1063                         | sym::html_favicon_url
1064                         | sym::html_logo_url
1065                         | sym::html_no_source
1066                         | sym::html_playground_url
1067                         | sym::html_root_url
1068                         | sym::inline
1069                         | sym::issue_tracker_base_url
1070                         | sym::keyword
1071                         | sym::masked
1072                         | sym::no_default_passes
1073                         | sym::no_inline
1074                         | sym::notable_trait
1075                         | sym::passes
1076                         | sym::plugins
1077                         | sym::fake_variadic => {}
1078
1079                         sym::test => {
1080                             if !self.check_test_attr(meta, hir_id) {
1081                                 is_valid = false;
1082                             }
1083                         }
1084
1085                         sym::primitive => {
1086                             if !self.tcx.features().rustdoc_internals {
1087                                 self.tcx.emit_spanned_lint(
1088                                     INVALID_DOC_ATTRIBUTES,
1089                                     hir_id,
1090                                     i_meta.span,
1091                                     errors::DocPrimitive,
1092                                 );
1093                             }
1094                         }
1095
1096                         _ => {
1097                             let path = rustc_ast_pretty::pprust::path_to_string(&i_meta.path);
1098                             if i_meta.has_name(sym::spotlight) {
1099                                 self.tcx.emit_spanned_lint(
1100                                     INVALID_DOC_ATTRIBUTES,
1101                                     hir_id,
1102                                     i_meta.span,
1103                                     errors::DocTestUnknownSpotlight {
1104                                         path,
1105                                         span: i_meta.span
1106                                     }
1107                                 );
1108                             } else if i_meta.has_name(sym::include) &&
1109                                     let Some(value) = i_meta.value_str() {
1110                                 let applicability = if list.len() == 1 {
1111                                     Applicability::MachineApplicable
1112                                 } else {
1113                                     Applicability::MaybeIncorrect
1114                                 };
1115                                 // If there are multiple attributes, the suggestion would suggest
1116                                 // deleting all of them, which is incorrect.
1117                                 self.tcx.emit_spanned_lint(
1118                                     INVALID_DOC_ATTRIBUTES,
1119                                     hir_id,
1120                                     i_meta.span,
1121                                     errors::DocTestUnknownInclude {
1122                                         path,
1123                                         value: value.to_string(),
1124                                         inner: if attr.style == AttrStyle::Inner { "!" } else { "" },
1125                                         sugg: (attr.meta().unwrap().span, applicability),
1126                                     }
1127                                 );
1128                             } else {
1129                                 self.tcx.emit_spanned_lint(
1130                                     INVALID_DOC_ATTRIBUTES,
1131                                     hir_id,
1132                                     i_meta.span,
1133                                     errors::DocTestUnknownAny { path }
1134                                 );
1135                             }
1136                             is_valid = false;
1137                         }
1138                     }
1139                 } else {
1140                     self.tcx.emit_spanned_lint(
1141                         INVALID_DOC_ATTRIBUTES,
1142                         hir_id,
1143                         meta.span(),
1144                         errors::DocInvalid,
1145                     );
1146                     is_valid = false;
1147                 }
1148             }
1149         }
1150
1151         is_valid
1152     }
1153
1154     /// Warns against some misuses of `#[pass_by_value]`
1155     fn check_pass_by_value(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1156         match target {
1157             Target::Struct | Target::Enum | Target::TyAlias => true,
1158             _ => {
1159                 self.tcx.sess.emit_err(errors::PassByValue { attr_span: attr.span, span });
1160                 false
1161             }
1162         }
1163     }
1164
1165     fn check_allow_incoherent_impl(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1166         match target {
1167             Target::Method(MethodKind::Inherent) => true,
1168             _ => {
1169                 self.tcx.sess.emit_err(errors::AllowIncoherentImpl { attr_span: attr.span, span });
1170                 false
1171             }
1172         }
1173     }
1174
1175     fn check_has_incoherent_inherent_impls(
1176         &self,
1177         attr: &Attribute,
1178         span: Span,
1179         target: Target,
1180     ) -> bool {
1181         match target {
1182             Target::Trait | Target::Struct | Target::Enum | Target::Union | Target::ForeignTy => {
1183                 true
1184             }
1185             _ => {
1186                 self.tcx
1187                     .sess
1188                     .emit_err(errors::HasIncoherentInherentImpl { attr_span: attr.span, span });
1189                 false
1190             }
1191         }
1192     }
1193
1194     /// Warns against some misuses of `#[must_use]`
1195     fn check_must_use(&self, hir_id: HirId, attr: &Attribute, target: Target) -> bool {
1196         if !matches!(
1197             target,
1198             Target::Fn
1199                 | Target::Enum
1200                 | Target::Struct
1201                 | Target::Union
1202                 | Target::Method(_)
1203                 | Target::ForeignFn
1204                 // `impl Trait` in return position can trip
1205                 // `unused_must_use` if `Trait` is marked as
1206                 // `#[must_use]`
1207                 | Target::Trait
1208         ) {
1209             let article = match target {
1210                 Target::ExternCrate
1211                 | Target::OpaqueTy
1212                 | Target::Enum
1213                 | Target::Impl
1214                 | Target::Expression
1215                 | Target::Arm
1216                 | Target::AssocConst
1217                 | Target::AssocTy => "an",
1218                 _ => "a",
1219             };
1220
1221             self.tcx.emit_spanned_lint(
1222                 UNUSED_ATTRIBUTES,
1223                 hir_id,
1224                 attr.span,
1225                 errors::MustUseNoEffect { article, target },
1226             );
1227         }
1228
1229         // For now, its always valid
1230         true
1231     }
1232
1233     /// Checks if `#[must_not_suspend]` is applied to a function. Returns `true` if valid.
1234     fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1235         match target {
1236             Target::Struct | Target::Enum | Target::Union | Target::Trait => true,
1237             _ => {
1238                 self.tcx.sess.emit_err(errors::MustNotSuspend { attr_span: attr.span, span });
1239                 false
1240             }
1241         }
1242     }
1243
1244     /// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid.
1245     fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1246         match target {
1247             Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => {}
1248             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1249             // `#[cold]` attribute with just a lint, because we previously
1250             // erroneously allowed it and some crates used it accidentally, to be compatible
1251             // with crates depending on them, we can't throw an error here.
1252             Target::Field | Target::Arm | Target::MacroDef => {
1253                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "cold");
1254             }
1255             _ => {
1256                 // FIXME: #[cold] was previously allowed on non-functions and some crates used
1257                 // this, so only emit a warning.
1258                 self.tcx.emit_spanned_lint(
1259                     UNUSED_ATTRIBUTES,
1260                     hir_id,
1261                     attr.span,
1262                     errors::Cold { span, on_crate: hir_id == CRATE_HIR_ID },
1263                 );
1264             }
1265         }
1266     }
1267
1268     /// Checks if `#[link]` is applied to an item other than a foreign module.
1269     fn check_link(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1270         if target == Target::ForeignMod
1271             && let hir::Node::Item(item) = self.tcx.hir().get(hir_id)
1272             && let Item { kind: ItemKind::ForeignMod { abi, .. }, .. } = item
1273             && !matches!(abi, Abi::Rust | Abi::RustIntrinsic | Abi::PlatformIntrinsic)
1274         {
1275             return;
1276         }
1277
1278         self.tcx.emit_spanned_lint(
1279             UNUSED_ATTRIBUTES,
1280             hir_id,
1281             attr.span,
1282             errors::Link { span: (target != Target::ForeignMod).then_some(span) },
1283         );
1284     }
1285
1286     /// Checks if `#[link_name]` is applied to an item other than a foreign function or static.
1287     fn check_link_name(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1288         match target {
1289             Target::ForeignFn | Target::ForeignStatic => {}
1290             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1291             // `#[link_name]` attribute with just a lint, because we previously
1292             // erroneously allowed it and some crates used it accidentally, to be compatible
1293             // with crates depending on them, we can't throw an error here.
1294             Target::Field | Target::Arm | Target::MacroDef => {
1295                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_name");
1296             }
1297             _ => {
1298                 // FIXME: #[cold] was previously allowed on non-functions/statics and some crates
1299                 // used this, so only emit a warning.
1300                 let attr_span = matches!(target, Target::ForeignMod).then_some(attr.span);
1301                 if let Some(s) = attr.value_str() {
1302                     self.tcx.emit_spanned_lint(
1303                         UNUSED_ATTRIBUTES,
1304                         hir_id,
1305                         attr.span,
1306                         errors::LinkName { span, attr_span, value: s.as_str() },
1307                     );
1308                 } else {
1309                     self.tcx.emit_spanned_lint(
1310                         UNUSED_ATTRIBUTES,
1311                         hir_id,
1312                         attr.span,
1313                         errors::LinkName { span, attr_span, value: "..." },
1314                     );
1315                 };
1316             }
1317         }
1318     }
1319
1320     /// Checks if `#[no_link]` is applied to an `extern crate`. Returns `true` if valid.
1321     fn check_no_link(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) -> bool {
1322         match target {
1323             Target::ExternCrate => true,
1324             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1325             // `#[no_link]` attribute with just a lint, because we previously
1326             // erroneously allowed it and some crates used it accidentally, to be compatible
1327             // with crates depending on them, we can't throw an error here.
1328             Target::Field | Target::Arm | Target::MacroDef => {
1329                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_link");
1330                 true
1331             }
1332             _ => {
1333                 self.tcx.sess.emit_err(errors::NoLink { attr_span: attr.span, span });
1334                 false
1335             }
1336         }
1337     }
1338
1339     fn is_impl_item(&self, hir_id: HirId) -> bool {
1340         matches!(self.tcx.hir().get(hir_id), hir::Node::ImplItem(..))
1341     }
1342
1343     /// Checks if `#[export_name]` is applied to a function or static. Returns `true` if valid.
1344     fn check_export_name(
1345         &self,
1346         hir_id: HirId,
1347         attr: &Attribute,
1348         span: Span,
1349         target: Target,
1350     ) -> bool {
1351         match target {
1352             Target::Static | Target::Fn => true,
1353             Target::Method(..) if self.is_impl_item(hir_id) => true,
1354             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1355             // `#[export_name]` attribute with just a lint, because we previously
1356             // erroneously allowed it and some crates used it accidentally, to be compatible
1357             // with crates depending on them, we can't throw an error here.
1358             Target::Field | Target::Arm | Target::MacroDef => {
1359                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "export_name");
1360                 true
1361             }
1362             _ => {
1363                 self.tcx.sess.emit_err(errors::ExportName { attr_span: attr.span, span });
1364                 false
1365             }
1366         }
1367     }
1368
1369     fn check_rustc_layout_scalar_valid_range(
1370         &self,
1371         attr: &Attribute,
1372         span: Span,
1373         target: Target,
1374     ) -> bool {
1375         if target != Target::Struct {
1376             self.tcx.sess.emit_err(errors::RustcLayoutScalarValidRangeNotStruct {
1377                 attr_span: attr.span,
1378                 span,
1379             });
1380             return false;
1381         }
1382
1383         let Some(list) = attr.meta_item_list() else {
1384             return false;
1385         };
1386
1387         if matches!(&list[..], &[NestedMetaItem::Lit(MetaItemLit { kind: LitKind::Int(..), .. })]) {
1388             true
1389         } else {
1390             self.tcx.sess.emit_err(errors::RustcLayoutScalarValidRangeArg { attr_span: attr.span });
1391             false
1392         }
1393     }
1394
1395     /// Checks if `#[rustc_legacy_const_generics]` is applied to a function and has a valid argument.
1396     fn check_rustc_legacy_const_generics(
1397         &self,
1398         hir_id: HirId,
1399         attr: &Attribute,
1400         span: Span,
1401         target: Target,
1402         item: Option<ItemLike<'_>>,
1403     ) -> bool {
1404         let is_function = matches!(target, Target::Fn);
1405         if !is_function {
1406             self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
1407                 attr_span: attr.span,
1408                 defn_span: span,
1409                 on_crate: hir_id == CRATE_HIR_ID,
1410             });
1411             return false;
1412         }
1413
1414         let Some(list) = attr.meta_item_list() else {
1415             // The attribute form is validated on AST.
1416             return false;
1417         };
1418
1419         let Some(ItemLike::Item(Item {
1420             kind: ItemKind::Fn(FnSig { decl, .. }, generics, _),
1421             ..
1422         }))  = item else {
1423             bug!("should be a function item");
1424         };
1425
1426         for param in generics.params {
1427             match param.kind {
1428                 hir::GenericParamKind::Const { .. } => {}
1429                 _ => {
1430                     self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsOnly {
1431                         attr_span: attr.span,
1432                         param_span: param.span,
1433                     });
1434                     return false;
1435                 }
1436             }
1437         }
1438
1439         if list.len() != generics.params.len() {
1440             self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndex {
1441                 attr_span: attr.span,
1442                 generics_span: generics.span,
1443             });
1444             return false;
1445         }
1446
1447         let arg_count = decl.inputs.len() as u128 + generics.params.len() as u128;
1448         let mut invalid_args = vec![];
1449         for meta in list {
1450             if let Some(LitKind::Int(val, _)) = meta.lit().map(|lit| &lit.kind) {
1451                 if *val >= arg_count {
1452                     let span = meta.span();
1453                     self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndexExceed {
1454                         span,
1455                         arg_count: arg_count as usize,
1456                     });
1457                     return false;
1458                 }
1459             } else {
1460                 invalid_args.push(meta.span());
1461             }
1462         }
1463
1464         if !invalid_args.is_empty() {
1465             self.tcx.sess.emit_err(errors::RustcLegacyConstGenericsIndexNegative { invalid_args });
1466             false
1467         } else {
1468             true
1469         }
1470     }
1471
1472     /// Helper function for checking that the provided attribute is only applied to a function or
1473     /// method.
1474     fn check_applied_to_fn_or_method(
1475         &self,
1476         hir_id: HirId,
1477         attr: &Attribute,
1478         span: Span,
1479         target: Target,
1480     ) -> bool {
1481         let is_function = matches!(target, Target::Fn | Target::Method(..));
1482         if !is_function {
1483             self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToFn {
1484                 attr_span: attr.span,
1485                 defn_span: span,
1486                 on_crate: hir_id == CRATE_HIR_ID,
1487             });
1488             false
1489         } else {
1490             true
1491         }
1492     }
1493
1494     /// Checks that the `#[rustc_lint_query_instability]` attribute is only applied to a function
1495     /// or method.
1496     fn check_rustc_lint_query_instability(
1497         &self,
1498         hir_id: HirId,
1499         attr: &Attribute,
1500         span: Span,
1501         target: Target,
1502     ) -> bool {
1503         self.check_applied_to_fn_or_method(hir_id, attr, span, target)
1504     }
1505
1506     /// Checks that the `#[rustc_lint_diagnostics]` attribute is only applied to a function or
1507     /// method.
1508     fn check_rustc_lint_diagnostics(
1509         &self,
1510         hir_id: HirId,
1511         attr: &Attribute,
1512         span: Span,
1513         target: Target,
1514     ) -> bool {
1515         self.check_applied_to_fn_or_method(hir_id, attr, span, target)
1516     }
1517
1518     /// Checks that the `#[rustc_lint_opt_ty]` attribute is only applied to a struct.
1519     fn check_rustc_lint_opt_ty(&self, attr: &Attribute, span: Span, target: Target) -> bool {
1520         match target {
1521             Target::Struct => true,
1522             _ => {
1523                 self.tcx.sess.emit_err(errors::RustcLintOptTy { attr_span: attr.span, span });
1524                 false
1525             }
1526         }
1527     }
1528
1529     /// Checks that the `#[rustc_lint_opt_deny_field_access]` attribute is only applied to a field.
1530     fn check_rustc_lint_opt_deny_field_access(
1531         &self,
1532         attr: &Attribute,
1533         span: Span,
1534         target: Target,
1535     ) -> bool {
1536         match target {
1537             Target::Field => true,
1538             _ => {
1539                 self.tcx
1540                     .sess
1541                     .emit_err(errors::RustcLintOptDenyFieldAccess { attr_span: attr.span, span });
1542                 false
1543             }
1544         }
1545     }
1546
1547     /// Checks that the dep-graph debugging attributes are only present when the query-dep-graph
1548     /// option is passed to the compiler.
1549     fn check_rustc_dirty_clean(&self, attr: &Attribute) -> bool {
1550         if self.tcx.sess.opts.unstable_opts.query_dep_graph {
1551             true
1552         } else {
1553             self.tcx.sess.emit_err(errors::RustcDirtyClean { span: attr.span });
1554             false
1555         }
1556     }
1557
1558     /// Checks if `#[link_section]` is applied to a function or static.
1559     fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1560         match target {
1561             Target::Static | Target::Fn | Target::Method(..) => {}
1562             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1563             // `#[link_section]` attribute with just a lint, because we previously
1564             // erroneously allowed it and some crates used it accidentally, to be compatible
1565             // with crates depending on them, we can't throw an error here.
1566             Target::Field | Target::Arm | Target::MacroDef => {
1567                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "link_section");
1568             }
1569             _ => {
1570                 // FIXME: #[link_section] was previously allowed on non-functions/statics and some
1571                 // crates used this, so only emit a warning.
1572                 self.tcx.emit_spanned_lint(
1573                     UNUSED_ATTRIBUTES,
1574                     hir_id,
1575                     attr.span,
1576                     errors::LinkSection { span },
1577                 );
1578             }
1579         }
1580     }
1581
1582     /// Checks if `#[no_mangle]` is applied to a function or static.
1583     fn check_no_mangle(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) {
1584         match target {
1585             Target::Static | Target::Fn => {}
1586             Target::Method(..) if self.is_impl_item(hir_id) => {}
1587             // FIXME(#80564): We permit struct fields, match arms and macro defs to have an
1588             // `#[no_mangle]` attribute with just a lint, because we previously
1589             // erroneously allowed it and some crates used it accidentally, to be compatible
1590             // with crates depending on them, we can't throw an error here.
1591             Target::Field | Target::Arm | Target::MacroDef => {
1592                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "no_mangle");
1593             }
1594             // FIXME: #[no_mangle] was previously allowed on non-functions/statics, this should be an error
1595             // The error should specify that the item that is wrong is specifically a *foreign* fn/static
1596             // otherwise the error seems odd
1597             Target::ForeignFn | Target::ForeignStatic => {
1598                 let foreign_item_kind = match target {
1599                     Target::ForeignFn => "function",
1600                     Target::ForeignStatic => "static",
1601                     _ => unreachable!(),
1602                 };
1603                 self.tcx.emit_spanned_lint(
1604                     UNUSED_ATTRIBUTES,
1605                     hir_id,
1606                     attr.span,
1607                     errors::NoMangleForeign { span, attr_span: attr.span, foreign_item_kind },
1608                 );
1609             }
1610             _ => {
1611                 // FIXME: #[no_mangle] was previously allowed on non-functions/statics and some
1612                 // crates used this, so only emit a warning.
1613                 self.tcx.emit_spanned_lint(
1614                     UNUSED_ATTRIBUTES,
1615                     hir_id,
1616                     attr.span,
1617                     errors::NoMangle { span },
1618                 );
1619             }
1620         }
1621     }
1622
1623     /// Checks if the `#[repr]` attributes on `item` are valid.
1624     fn check_repr(
1625         &self,
1626         attrs: &[Attribute],
1627         span: Span,
1628         target: Target,
1629         item: Option<ItemLike<'_>>,
1630         hir_id: HirId,
1631     ) {
1632         // Extract the names of all repr hints, e.g., [foo, bar, align] for:
1633         // ```
1634         // #[repr(foo)]
1635         // #[repr(bar, align(8))]
1636         // ```
1637         let hints: Vec<_> = attrs
1638             .iter()
1639             .filter(|attr| attr.has_name(sym::repr))
1640             .filter_map(|attr| attr.meta_item_list())
1641             .flatten()
1642             .collect();
1643
1644         let mut int_reprs = 0;
1645         let mut is_c = false;
1646         let mut is_simd = false;
1647         let mut is_transparent = false;
1648
1649         for hint in &hints {
1650             if !hint.is_meta_item() {
1651                 self.tcx.sess.emit_err(errors::ReprIdent { span: hint.span() });
1652                 continue;
1653             }
1654
1655             match hint.name_or_empty() {
1656                 sym::C => {
1657                     is_c = true;
1658                     match target {
1659                         Target::Struct | Target::Union | Target::Enum => continue,
1660                         _ => {
1661                             self.tcx.sess.emit_err(AttrApplication::StructEnumUnion {
1662                                 hint_span: hint.span(),
1663                                 span,
1664                             });
1665                         }
1666                     }
1667                 }
1668                 sym::align => {
1669                     if let (Target::Fn, false) = (target, self.tcx.features().fn_align) {
1670                         feature_err(
1671                             &self.tcx.sess.parse_sess,
1672                             sym::fn_align,
1673                             hint.span(),
1674                             "`repr(align)` attributes on functions are unstable",
1675                         )
1676                         .emit();
1677                     }
1678
1679                     match target {
1680                         Target::Struct | Target::Union | Target::Enum | Target::Fn => continue,
1681                         _ => {
1682                             self.tcx.sess.emit_err(AttrApplication::StructEnumFunctionUnion {
1683                                 hint_span: hint.span(),
1684                                 span,
1685                             });
1686                         }
1687                     }
1688                 }
1689                 sym::packed => {
1690                     if target != Target::Struct && target != Target::Union {
1691                         self.tcx.sess.emit_err(AttrApplication::StructUnion {
1692                             hint_span: hint.span(),
1693                             span,
1694                         });
1695                     } else {
1696                         continue;
1697                     }
1698                 }
1699                 sym::simd => {
1700                     is_simd = true;
1701                     if target != Target::Struct {
1702                         self.tcx
1703                             .sess
1704                             .emit_err(AttrApplication::Struct { hint_span: hint.span(), span });
1705                     } else {
1706                         continue;
1707                     }
1708                 }
1709                 sym::transparent => {
1710                     is_transparent = true;
1711                     match target {
1712                         Target::Struct | Target::Union | Target::Enum => continue,
1713                         _ => {
1714                             self.tcx.sess.emit_err(AttrApplication::StructEnumUnion {
1715                                 hint_span: hint.span(),
1716                                 span,
1717                             });
1718                         }
1719                     }
1720                 }
1721                 sym::i8
1722                 | sym::u8
1723                 | sym::i16
1724                 | sym::u16
1725                 | sym::i32
1726                 | sym::u32
1727                 | sym::i64
1728                 | sym::u64
1729                 | sym::i128
1730                 | sym::u128
1731                 | sym::isize
1732                 | sym::usize => {
1733                     int_reprs += 1;
1734                     if target != Target::Enum {
1735                         self.tcx
1736                             .sess
1737                             .emit_err(AttrApplication::Enum { hint_span: hint.span(), span });
1738                     } else {
1739                         continue;
1740                     }
1741                 }
1742                 _ => {
1743                     self.tcx.sess.emit_err(UnrecognizedReprHint { span: hint.span() });
1744                     continue;
1745                 }
1746             };
1747         }
1748
1749         // Just point at all repr hints if there are any incompatibilities.
1750         // This is not ideal, but tracking precisely which ones are at fault is a huge hassle.
1751         let hint_spans = hints.iter().map(|hint| hint.span());
1752
1753         // Error on repr(transparent, <anything else>).
1754         if is_transparent && hints.len() > 1 {
1755             let hint_spans: Vec<_> = hint_spans.clone().collect();
1756             self.tcx
1757                 .sess
1758                 .emit_err(TransparentIncompatible { hint_spans, target: target.to_string() });
1759         }
1760         // Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8)
1761         if (int_reprs > 1)
1762             || (is_simd && is_c)
1763             || (int_reprs == 1
1764                 && is_c
1765                 && item.map_or(false, |item| {
1766                     if let ItemLike::Item(item) = item {
1767                         return is_c_like_enum(item);
1768                     }
1769                     return false;
1770                 }))
1771         {
1772             self.tcx.emit_spanned_lint(
1773                 CONFLICTING_REPR_HINTS,
1774                 hir_id,
1775                 hint_spans.collect::<Vec<Span>>(),
1776                 errors::ReprConflicting,
1777             );
1778         }
1779     }
1780
1781     fn check_used(&self, attrs: &[Attribute], target: Target) {
1782         let mut used_linker_span = None;
1783         let mut used_compiler_span = None;
1784         for attr in attrs.iter().filter(|attr| attr.has_name(sym::used)) {
1785             if target != Target::Static {
1786                 self.tcx.sess.emit_err(errors::UsedStatic { span: attr.span });
1787             }
1788             let inner = attr.meta_item_list();
1789             match inner.as_deref() {
1790                 Some([item]) if item.has_name(sym::linker) => {
1791                     if used_linker_span.is_none() {
1792                         used_linker_span = Some(attr.span);
1793                     }
1794                 }
1795                 Some([item]) if item.has_name(sym::compiler) => {
1796                     if used_compiler_span.is_none() {
1797                         used_compiler_span = Some(attr.span);
1798                     }
1799                 }
1800                 Some(_) => {
1801                     // This error case is handled in rustc_hir_analysis::collect.
1802                 }
1803                 None => {
1804                     // Default case (compiler) when arg isn't defined.
1805                     if used_compiler_span.is_none() {
1806                         used_compiler_span = Some(attr.span);
1807                     }
1808                 }
1809             }
1810         }
1811         if let (Some(linker_span), Some(compiler_span)) = (used_linker_span, used_compiler_span) {
1812             self.tcx
1813                 .sess
1814                 .emit_err(errors::UsedCompilerLinker { spans: vec![linker_span, compiler_span] });
1815         }
1816     }
1817
1818     /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
1819     /// (Allows proc_macro functions)
1820     fn check_allow_internal_unstable(
1821         &self,
1822         hir_id: HirId,
1823         attr: &Attribute,
1824         span: Span,
1825         target: Target,
1826         attrs: &[Attribute],
1827     ) -> bool {
1828         debug!("Checking target: {:?}", target);
1829         match target {
1830             Target::Fn => {
1831                 for attr in attrs {
1832                     if self.tcx.sess.is_proc_macro_attr(attr) {
1833                         debug!("Is proc macro attr");
1834                         return true;
1835                     }
1836                 }
1837                 debug!("Is not proc macro attr");
1838                 false
1839             }
1840             Target::MacroDef => true,
1841             // FIXME(#80564): We permit struct fields and match arms to have an
1842             // `#[allow_internal_unstable]` attribute with just a lint, because we previously
1843             // erroneously allowed it and some crates used it accidentally, to be compatible
1844             // with crates depending on them, we can't throw an error here.
1845             Target::Field | Target::Arm => {
1846                 self.inline_attr_str_error_without_macro_def(
1847                     hir_id,
1848                     attr,
1849                     "allow_internal_unstable",
1850                 );
1851                 true
1852             }
1853             _ => {
1854                 self.tcx
1855                     .sess
1856                     .emit_err(errors::AllowInternalUnstable { attr_span: attr.span, span });
1857                 false
1858             }
1859         }
1860     }
1861
1862     /// Checks if the items on the `#[debugger_visualizer]` attribute are valid.
1863     fn check_debugger_visualizer(&self, attr: &Attribute, target: Target) -> bool {
1864         match target {
1865             Target::Mod => {}
1866             _ => {
1867                 self.tcx.sess.emit_err(errors::DebugVisualizerPlacement { span: attr.span });
1868                 return false;
1869             }
1870         }
1871
1872         let Some(hints) = attr.meta_item_list() else {
1873             self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: attr.span });
1874             return false;
1875         };
1876
1877         let hint = match hints.len() {
1878             1 => &hints[0],
1879             _ => {
1880                 self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: attr.span });
1881                 return false;
1882             }
1883         };
1884
1885         let Some(meta_item) = hint.meta_item() else {
1886             self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: attr.span });
1887             return false;
1888         };
1889
1890         let visualizer_path = match (meta_item.name_or_empty(), meta_item.value_str()) {
1891             (sym::natvis_file, Some(value)) => value,
1892             (sym::gdb_script_file, Some(value)) => value,
1893             (_, _) => {
1894                 self.tcx.sess.emit_err(errors::DebugVisualizerInvalid { span: meta_item.span });
1895                 return false;
1896             }
1897         };
1898
1899         let file =
1900             match resolve_path(&self.tcx.sess.parse_sess, visualizer_path.as_str(), attr.span) {
1901                 Ok(file) => file,
1902                 Err(mut err) => {
1903                     err.emit();
1904                     return false;
1905                 }
1906             };
1907
1908         match std::fs::File::open(&file) {
1909             Ok(_) => true,
1910             Err(error) => {
1911                 self.tcx.sess.emit_err(DebugVisualizerUnreadable {
1912                     span: meta_item.span,
1913                     file: &file,
1914                     error,
1915                 });
1916                 false
1917             }
1918         }
1919     }
1920
1921     /// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
1922     /// (Allows proc_macro functions)
1923     fn check_rustc_allow_const_fn_unstable(
1924         &self,
1925         hir_id: HirId,
1926         attr: &Attribute,
1927         span: Span,
1928         target: Target,
1929     ) -> bool {
1930         match target {
1931             Target::Fn | Target::Method(_)
1932                 if self.tcx.is_const_fn_raw(self.tcx.hir().local_def_id(hir_id).to_def_id()) =>
1933             {
1934                 true
1935             }
1936             // FIXME(#80564): We permit struct fields and match arms to have an
1937             // `#[allow_internal_unstable]` attribute with just a lint, because we previously
1938             // erroneously allowed it and some crates used it accidentally, to be compatible
1939             // with crates depending on them, we can't throw an error here.
1940             Target::Field | Target::Arm | Target::MacroDef => {
1941                 self.inline_attr_str_error_with_macro_def(hir_id, attr, "allow_internal_unstable");
1942                 true
1943             }
1944             _ => {
1945                 self.tcx
1946                     .sess
1947                     .emit_err(errors::RustcAllowConstFnUnstable { attr_span: attr.span, span });
1948                 false
1949             }
1950         }
1951     }
1952
1953     fn check_rustc_std_internal_symbol(
1954         &self,
1955         attr: &Attribute,
1956         span: Span,
1957         target: Target,
1958     ) -> bool {
1959         match target {
1960             Target::Fn | Target::Static => true,
1961             _ => {
1962                 self.tcx
1963                     .sess
1964                     .emit_err(errors::RustcStdInternalSymbol { attr_span: attr.span, span });
1965                 false
1966             }
1967         }
1968     }
1969
1970     /// `#[const_trait]` only applies to traits.
1971     fn check_const_trait(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
1972         match target {
1973             Target::Trait => true,
1974             _ => {
1975                 self.tcx.sess.emit_err(errors::ConstTrait { attr_span: attr.span });
1976                 false
1977             }
1978         }
1979     }
1980
1981     fn check_stability_promotable(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
1982         match target {
1983             Target::Expression => {
1984                 self.tcx.sess.emit_err(errors::StabilityPromotable { attr_span: attr.span });
1985                 false
1986             }
1987             _ => true,
1988         }
1989     }
1990
1991     fn check_link_ordinal(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
1992         match target {
1993             Target::ForeignFn | Target::ForeignStatic => true,
1994             _ => {
1995                 self.tcx.sess.emit_err(errors::LinkOrdinal { attr_span: attr.span });
1996                 false
1997             }
1998         }
1999     }
2000
2001     fn check_deprecated(&self, hir_id: HirId, attr: &Attribute, _span: Span, target: Target) {
2002         match target {
2003             Target::Closure | Target::Expression | Target::Statement | Target::Arm => {
2004                 self.tcx.emit_spanned_lint(
2005                     UNUSED_ATTRIBUTES,
2006                     hir_id,
2007                     attr.span,
2008                     errors::Deprecated,
2009                 );
2010             }
2011             _ => {}
2012         }
2013     }
2014
2015     fn check_macro_use(&self, hir_id: HirId, attr: &Attribute, target: Target) {
2016         let name = attr.name_or_empty();
2017         match target {
2018             Target::ExternCrate | Target::Mod => {}
2019             _ => {
2020                 self.tcx.emit_spanned_lint(
2021                     UNUSED_ATTRIBUTES,
2022                     hir_id,
2023                     attr.span,
2024                     errors::MacroUse { name },
2025                 );
2026             }
2027         }
2028     }
2029
2030     fn check_macro_export(&self, hir_id: HirId, attr: &Attribute, target: Target) {
2031         if target != Target::MacroDef {
2032             self.tcx.emit_spanned_lint(UNUSED_ATTRIBUTES, hir_id, attr.span, errors::MacroExport);
2033         }
2034     }
2035
2036     fn check_plugin_registrar(&self, hir_id: HirId, attr: &Attribute, target: Target) {
2037         if target != Target::Fn {
2038             self.tcx.emit_spanned_lint(
2039                 UNUSED_ATTRIBUTES,
2040                 hir_id,
2041                 attr.span,
2042                 errors::PluginRegistrar,
2043             );
2044         }
2045     }
2046
2047     fn check_unused_attribute(&self, hir_id: HirId, attr: &Attribute) {
2048         // Warn on useless empty attributes.
2049         let note = if matches!(
2050             attr.name_or_empty(),
2051             sym::macro_use
2052                 | sym::allow
2053                 | sym::expect
2054                 | sym::warn
2055                 | sym::deny
2056                 | sym::forbid
2057                 | sym::feature
2058                 | sym::repr
2059                 | sym::target_feature
2060         ) && attr.meta_item_list().map_or(false, |list| list.is_empty())
2061         {
2062             errors::UnusedNote::EmptyList { name: attr.name_or_empty() }
2063         } else if matches!(
2064                 attr.name_or_empty(),
2065                 sym::allow | sym::warn | sym::deny | sym::forbid | sym::expect
2066             ) && let Some(meta) = attr.meta_item_list()
2067             && meta.len() == 1
2068             && let Some(item) = meta[0].meta_item()
2069             && let MetaItemKind::NameValue(_) = &item.kind
2070             && item.path == sym::reason
2071         {
2072             errors::UnusedNote::NoLints { name: attr.name_or_empty() }
2073         } else if attr.name_or_empty() == sym::default_method_body_is_const {
2074             errors::UnusedNote::DefaultMethodBodyConst
2075         } else {
2076             return;
2077         };
2078
2079         self.tcx.emit_spanned_lint(
2080             UNUSED_ATTRIBUTES,
2081             hir_id,
2082             attr.span,
2083             errors::Unused { attr_span: attr.span, note },
2084         );
2085     }
2086
2087     fn check_proc_macro(&self, hir_id: HirId, target: Target, kind: ProcMacroKind) {
2088         let expected_input_count = match kind {
2089             ProcMacroKind::Attribute => 2,
2090             ProcMacroKind::Derive | ProcMacroKind::FunctionLike => 1,
2091         };
2092
2093         let expected_signature = match kind {
2094             ProcMacroKind::Attribute => "fn(TokenStream, TokenStream) -> TokenStream",
2095             ProcMacroKind::Derive | ProcMacroKind::FunctionLike => "fn(TokenStream) -> TokenStream",
2096         };
2097
2098         let tcx = self.tcx;
2099         if target == Target::Fn {
2100             let Some(tokenstream) = tcx.get_diagnostic_item(sym::TokenStream) else {return};
2101             let tokenstream = tcx.type_of(tokenstream);
2102
2103             let id = hir_id.expect_owner();
2104             let hir_sig = tcx.hir().fn_sig_by_hir_id(hir_id).unwrap();
2105
2106             let sig = tcx.fn_sig(id);
2107
2108             if sig.abi() != Abi::Rust {
2109                 tcx.sess
2110                     .emit_err(ProcMacroInvalidAbi { span: hir_sig.span, abi: sig.abi().name() });
2111                 self.abort.set(true);
2112             }
2113
2114             if sig.unsafety() == Unsafety::Unsafe {
2115                 tcx.sess.emit_err(ProcMacroUnsafe { span: hir_sig.span });
2116                 self.abort.set(true);
2117             }
2118
2119             let output = sig.output().skip_binder();
2120
2121             // Typecheck the output
2122             if tcx.normalize_erasing_regions(ParamEnv::empty(), output) != tokenstream {
2123                 tcx.sess.emit_err(ProcMacroTypeError {
2124                     span: hir_sig.decl.output.span(),
2125                     found: output,
2126                     kind,
2127                     expected_signature,
2128                 });
2129                 self.abort.set(true);
2130             }
2131
2132             // Typecheck "expected_input_count" inputs, emitting
2133             // `ProcMacroMissingArguments` if there are not enough.
2134             if let Some(args) = sig.inputs().skip_binder().get(0..expected_input_count) {
2135                 for (arg, input) in args.iter().zip(hir_sig.decl.inputs) {
2136                     if tcx.normalize_erasing_regions(ParamEnv::empty(), *arg) != tokenstream {
2137                         tcx.sess.emit_err(ProcMacroTypeError {
2138                             span: input.span,
2139                             found: *arg,
2140                             kind,
2141                             expected_signature,
2142                         });
2143                         self.abort.set(true);
2144                     }
2145                 }
2146             } else {
2147                 tcx.sess.emit_err(ProcMacroMissingArguments {
2148                     expected_input_count,
2149                     span: hir_sig.span,
2150                     kind,
2151                     expected_signature,
2152                 });
2153                 self.abort.set(true);
2154             }
2155
2156             // Check that there are not too many arguments
2157             let body_id = tcx.hir().body_owned_by(id.def_id);
2158             let excess = tcx.hir().body(body_id).params.get(expected_input_count..);
2159             if let Some(excess @ [begin @ end] | excess @ [begin, .., end]) = excess {
2160                 tcx.sess.emit_err(ProcMacroDiffArguments {
2161                     span: begin.span.to(end.span),
2162                     count: excess.len(),
2163                     kind,
2164                     expected_signature,
2165                 });
2166                 self.abort.set(true);
2167             }
2168         }
2169     }
2170 }
2171
2172 impl<'tcx> Visitor<'tcx> for CheckAttrVisitor<'tcx> {
2173     type NestedFilter = nested_filter::OnlyBodies;
2174
2175     fn nested_visit_map(&mut self) -> Self::Map {
2176         self.tcx.hir()
2177     }
2178
2179     fn visit_item(&mut self, item: &'tcx Item<'tcx>) {
2180         // Historically we've run more checks on non-exported than exported macros,
2181         // so this lets us continue to run them while maintaining backwards compatibility.
2182         // In the long run, the checks should be harmonized.
2183         if let ItemKind::Macro(ref macro_def, _) = item.kind {
2184             let def_id = item.owner_id.to_def_id();
2185             if macro_def.macro_rules && !self.tcx.has_attr(def_id, sym::macro_export) {
2186                 check_non_exported_macro_for_invalid_attrs(self.tcx, item);
2187             }
2188         }
2189
2190         let target = Target::from_item(item);
2191         self.check_attributes(item.hir_id(), item.span, target, Some(ItemLike::Item(item)));
2192         intravisit::walk_item(self, item)
2193     }
2194
2195     fn visit_generic_param(&mut self, generic_param: &'tcx hir::GenericParam<'tcx>) {
2196         let target = Target::from_generic_param(generic_param);
2197         self.check_attributes(generic_param.hir_id, generic_param.span, target, None);
2198         intravisit::walk_generic_param(self, generic_param)
2199     }
2200
2201     fn visit_trait_item(&mut self, trait_item: &'tcx TraitItem<'tcx>) {
2202         let target = Target::from_trait_item(trait_item);
2203         self.check_attributes(trait_item.hir_id(), trait_item.span, target, None);
2204         intravisit::walk_trait_item(self, trait_item)
2205     }
2206
2207     fn visit_field_def(&mut self, struct_field: &'tcx hir::FieldDef<'tcx>) {
2208         self.check_attributes(struct_field.hir_id, struct_field.span, Target::Field, None);
2209         intravisit::walk_field_def(self, struct_field);
2210     }
2211
2212     fn visit_arm(&mut self, arm: &'tcx hir::Arm<'tcx>) {
2213         self.check_attributes(arm.hir_id, arm.span, Target::Arm, None);
2214         intravisit::walk_arm(self, arm);
2215     }
2216
2217     fn visit_foreign_item(&mut self, f_item: &'tcx ForeignItem<'tcx>) {
2218         let target = Target::from_foreign_item(f_item);
2219         self.check_attributes(f_item.hir_id(), f_item.span, target, Some(ItemLike::ForeignItem));
2220         intravisit::walk_foreign_item(self, f_item)
2221     }
2222
2223     fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
2224         let target = target_from_impl_item(self.tcx, impl_item);
2225         self.check_attributes(impl_item.hir_id(), impl_item.span, target, None);
2226         intravisit::walk_impl_item(self, impl_item)
2227     }
2228
2229     fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) {
2230         // When checking statements ignore expressions, they will be checked later.
2231         if let hir::StmtKind::Local(ref l) = stmt.kind {
2232             self.check_attributes(l.hir_id, stmt.span, Target::Statement, None);
2233         }
2234         intravisit::walk_stmt(self, stmt)
2235     }
2236
2237     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
2238         let target = match expr.kind {
2239             hir::ExprKind::Closure { .. } => Target::Closure,
2240             _ => Target::Expression,
2241         };
2242
2243         self.check_attributes(expr.hir_id, expr.span, target, None);
2244         intravisit::walk_expr(self, expr)
2245     }
2246
2247     fn visit_expr_field(&mut self, field: &'tcx hir::ExprField<'tcx>) {
2248         self.check_attributes(field.hir_id, field.span, Target::ExprField, None);
2249         intravisit::walk_expr_field(self, field)
2250     }
2251
2252     fn visit_variant(&mut self, variant: &'tcx hir::Variant<'tcx>) {
2253         self.check_attributes(variant.hir_id, variant.span, Target::Variant, None);
2254         intravisit::walk_variant(self, variant)
2255     }
2256
2257     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
2258         self.check_attributes(param.hir_id, param.span, Target::Param, None);
2259
2260         intravisit::walk_param(self, param);
2261     }
2262
2263     fn visit_pat_field(&mut self, field: &'tcx hir::PatField<'tcx>) {
2264         self.check_attributes(field.hir_id, field.span, Target::PatField, None);
2265         intravisit::walk_pat_field(self, field);
2266     }
2267 }
2268
2269 fn is_c_like_enum(item: &Item<'_>) -> bool {
2270     if let ItemKind::Enum(ref def, _) = item.kind {
2271         for variant in def.variants {
2272             match variant.data {
2273                 hir::VariantData::Unit(..) => { /* continue */ }
2274                 _ => return false,
2275             }
2276         }
2277         true
2278     } else {
2279         false
2280     }
2281 }
2282
2283 // FIXME: Fix "Cannot determine resolution" error and remove built-in macros
2284 // from this check.
2285 fn check_invalid_crate_level_attr(tcx: TyCtxt<'_>, attrs: &[Attribute]) {
2286     // Check for builtin attributes at the crate level
2287     // which were unsuccessfully resolved due to cannot determine
2288     // resolution for the attribute macro error.
2289     const ATTRS_TO_CHECK: &[Symbol] = &[
2290         sym::macro_export,
2291         sym::repr,
2292         sym::path,
2293         sym::automatically_derived,
2294         sym::start,
2295         sym::rustc_main,
2296         sym::unix_sigpipe,
2297         sym::derive,
2298         sym::test,
2299         sym::test_case,
2300         sym::global_allocator,
2301         sym::bench,
2302     ];
2303
2304     for attr in attrs {
2305         // This function should only be called with crate attributes
2306         // which are inner attributes always but lets check to make sure
2307         if attr.style == AttrStyle::Inner {
2308             for attr_to_check in ATTRS_TO_CHECK {
2309                 if attr.has_name(*attr_to_check) {
2310                     tcx.sess.emit_err(InvalidAttrAtCrateLevel {
2311                         span: attr.span,
2312                         snippet: tcx.sess.source_map().span_to_snippet(attr.span).ok(),
2313                         name: *attr_to_check,
2314                     });
2315                 }
2316             }
2317         }
2318     }
2319 }
2320
2321 fn check_non_exported_macro_for_invalid_attrs(tcx: TyCtxt<'_>, item: &Item<'_>) {
2322     let attrs = tcx.hir().attrs(item.hir_id());
2323
2324     for attr in attrs {
2325         if attr.has_name(sym::inline) {
2326             tcx.sess.emit_err(errors::NonExportedMacroInvalidAttrs { attr_span: attr.span });
2327         }
2328     }
2329 }
2330
2331 fn check_mod_attrs(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
2332     let check_attr_visitor = &mut CheckAttrVisitor { tcx, abort: Cell::new(false) };
2333     tcx.hir().visit_item_likes_in_module(module_def_id, check_attr_visitor);
2334     if module_def_id.is_top_level_module() {
2335         check_attr_visitor.check_attributes(CRATE_HIR_ID, DUMMY_SP, Target::Mod, None);
2336         check_invalid_crate_level_attr(tcx, tcx.hir().krate_attrs());
2337     }
2338     if check_attr_visitor.abort.get() {
2339         tcx.sess.abort_if_errors()
2340     }
2341 }
2342
2343 pub(crate) fn provide(providers: &mut Providers) {
2344     *providers = Providers { check_mod_attrs, ..*providers };
2345 }
2346
2347 fn check_duplicates(
2348     tcx: TyCtxt<'_>,
2349     attr: &Attribute,
2350     hir_id: HirId,
2351     duplicates: AttributeDuplicates,
2352     seen: &mut FxHashMap<Symbol, Span>,
2353 ) {
2354     use AttributeDuplicates::*;
2355     if matches!(duplicates, WarnFollowingWordOnly) && !attr.is_word() {
2356         return;
2357     }
2358     match duplicates {
2359         DuplicatesOk => {}
2360         WarnFollowing | FutureWarnFollowing | WarnFollowingWordOnly | FutureWarnPreceding => {
2361             match seen.entry(attr.name_or_empty()) {
2362                 Entry::Occupied(mut entry) => {
2363                     let (this, other) = if matches!(duplicates, FutureWarnPreceding) {
2364                         let to_remove = entry.insert(attr.span);
2365                         (to_remove, attr.span)
2366                     } else {
2367                         (attr.span, *entry.get())
2368                     };
2369                     tcx.emit_spanned_lint(
2370                         UNUSED_ATTRIBUTES,
2371                         hir_id,
2372                         this,
2373                         errors::UnusedDuplicate {
2374                             this,
2375                             other,
2376                             warning: matches!(
2377                                 duplicates,
2378                                 FutureWarnFollowing | FutureWarnPreceding
2379                             )
2380                             .then_some(()),
2381                         },
2382                     );
2383                 }
2384                 Entry::Vacant(entry) => {
2385                     entry.insert(attr.span);
2386                 }
2387             }
2388         }
2389         ErrorFollowing | ErrorPreceding => match seen.entry(attr.name_or_empty()) {
2390             Entry::Occupied(mut entry) => {
2391                 let (this, other) = if matches!(duplicates, ErrorPreceding) {
2392                     let to_remove = entry.insert(attr.span);
2393                     (to_remove, attr.span)
2394                 } else {
2395                     (attr.span, *entry.get())
2396                 };
2397                 tcx.sess.emit_err(errors::UnusedMultiple {
2398                     this,
2399                     other,
2400                     name: attr.name_or_empty(),
2401                 });
2402             }
2403             Entry::Vacant(entry) => {
2404                 entry.insert(attr.span);
2405             }
2406         },
2407     }
2408 }