compiler/rustc_feature/src/builtin_attrs.rs

   1 //! Built-in attributes and `cfg` flag gating.
   2
   3 use AttributeGate::*;
   4 use AttributeType::*;
   5
   6 use crate::{Features, Stability};
   7
   8 use rustc_data_structures::fx::FxHashMap;
   9 use rustc_span::symbol::{sym, Symbol};
  10
  11 use std::lazy::SyncLazy;
  12
  13 type GateFn = fn(&Features) -> bool;
  14
  15 macro_rules! cfg_fn {
  16     ($field: ident) => {
  17         (|features| features.$field) as GateFn
  18     };
  19 }
  20
  21 pub type GatedCfg = (Symbol, Symbol, GateFn);
  22
  23 /// `cfg(...)`'s that are feature gated.
  24 const GATED_CFGS: &[GatedCfg] = &[
  25     // (name in cfg, feature, function to check if the feature is enabled)
  26     (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
  27     (sym::target_has_atomic, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
  28     (sym::target_has_atomic_load_store, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
  29     (
  30         sym::target_has_atomic_equal_alignment,
  31         sym::cfg_target_has_atomic,
  32         cfg_fn!(cfg_target_has_atomic),
  33     ),
  34     (sym::sanitize, sym::cfg_sanitize, cfg_fn!(cfg_sanitize)),
  35     (sym::version, sym::cfg_version, cfg_fn!(cfg_version)),
  36     (sym::panic, sym::cfg_panic, cfg_fn!(cfg_panic)),
  37 ];
  38
  39 /// Find a gated cfg determined by the `pred`icate which is given the cfg's name.
  40 pub fn find_gated_cfg(pred: impl Fn(Symbol) -> bool) -> Option<&'static GatedCfg> {
  41     GATED_CFGS.iter().find(|(cfg_sym, ..)| pred(*cfg_sym))
  42 }
  43
  44 // If you change this, please modify `src/doc/unstable-book` as well. You must
  45 // move that documentation into the relevant place in the other docs, and
  46 // remove the chapter on the flag.
  47
  48 #[derive(Copy, Clone, PartialEq, Debug)]
  49 pub enum AttributeType {
  50     /// Normal, builtin attribute that is consumed
  51     /// by the compiler before the unused_attribute check
  52     Normal,
  53
  54     /// Builtin attribute that may not be consumed by the compiler
  55     /// before the unused_attribute check. These attributes
  56     /// will be ignored by the unused_attribute lint
  57     AssumedUsed,
  58
  59     /// Builtin attribute that is only allowed at the crate level
  60     CrateLevel,
  61 }
  62
  63 #[derive(Clone, Copy)]
  64 pub enum AttributeGate {
  65     /// Is gated by a given feature gate, reason
  66     /// and function to check if enabled
  67     Gated(Stability, Symbol, &'static str, fn(&Features) -> bool),
  68
  69     /// Ungated attribute, can be used on all release channels
  70     Ungated,
  71 }
  72
  73 // fn() is not Debug
  74 impl std::fmt::Debug for AttributeGate {
  75     fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
  76         match *self {
  77             Self::Gated(ref stab, name, expl, _) => {
  78                 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl)
  79             }
  80             Self::Ungated => write!(fmt, "Ungated"),
  81         }
  82     }
  83 }
  84
  85 impl AttributeGate {
  86     fn is_deprecated(&self) -> bool {
  87         matches!(*self, Self::Gated(Stability::Deprecated(_, _), ..))
  88     }
  89 }
  90
  91 /// A template that the attribute input must match.
  92 /// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
  93 #[derive(Clone, Copy, Default)]
  94 pub struct AttributeTemplate {
  95     pub word: bool,
  96     pub list: Option<&'static str>,
  97     pub name_value_str: Option<&'static str>,
  98 }
  99
 100 /// A convenience macro for constructing attribute templates.
 101 /// E.g., `template!(Word, List: "description")` means that the attribute
 102 /// supports forms `#[attr]` and `#[attr(description)]`.
 103 macro_rules! template {
 104     (Word) => { template!(@ true, None, None) };
 105     (List: $descr: expr) => { template!(@ false, Some($descr), None) };
 106     (NameValueStr: $descr: expr) => { template!(@ false, None, Some($descr)) };
 107     (Word, List: $descr: expr) => { template!(@ true, Some($descr), None) };
 108     (Word, NameValueStr: $descr: expr) => { template!(@ true, None, Some($descr)) };
 109     (List: $descr1: expr, NameValueStr: $descr2: expr) => {
 110         template!(@ false, Some($descr1), Some($descr2))
 111     };
 112     (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
 113         template!(@ true, Some($descr1), Some($descr2))
 114     };
 115     (@ $word: expr, $list: expr, $name_value_str: expr) => { AttributeTemplate {
 116         word: $word, list: $list, name_value_str: $name_value_str
 117     } };
 118 }
 119
 120 macro_rules! ungated {
 121     ($attr:ident, $typ:expr, $tpl:expr $(,)?) => {
 122         (sym::$attr, $typ, $tpl, Ungated)
 123     };
 124 }
 125
 126 macro_rules! gated {
 127     ($attr:ident, $typ:expr, $tpl:expr, $gate:ident, $msg:expr $(,)?) => {
 128         (sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$gate, $msg, cfg_fn!($gate)))
 129     };
 130     ($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
 131         (sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$attr, $msg, cfg_fn!($attr)))
 132     };
 133 }
 134
 135 macro_rules! rustc_attr {
 136     (TEST, $attr:ident, $typ:expr, $tpl:expr $(,)?) => {
 137         rustc_attr!(
 138             $attr,
 139             $typ,
 140             $tpl,
 141             concat!(
 142                 "the `#[",
 143                 stringify!($attr),
 144                 "]` attribute is just used for rustc unit tests \
 145                 and will never be stable",
 146             ),
 147         )
 148     };
 149     ($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
 150         (
 151             sym::$attr,
 152             $typ,
 153             $tpl,
 154             Gated(Stability::Unstable, sym::rustc_attrs, $msg, cfg_fn!(rustc_attrs)),
 155         )
 156     };
 157 }
 158
 159 macro_rules! experimental {
 160     ($attr:ident) => {
 161         concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
 162     };
 163 }
 164
 165 const IMPL_DETAIL: &str = "internal implementation detail";
 166 const INTERNAL_UNSTABLE: &str = "this is an internal attribute that will never be stable";
 167
 168 pub type BuiltinAttribute = (Symbol, AttributeType, AttributeTemplate, AttributeGate);
 169
 170 /// Attributes that have a special meaning to rustc or rustdoc.
 171 #[rustfmt::skip]
 172 pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
 173     // ==========================================================================
 174     // Stable attributes:
 175     // ==========================================================================
 176
 177     // Conditional compilation:
 178     ungated!(cfg, Normal, template!(List: "predicate")),
 179     ungated!(cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ...")),
 180
 181     // Testing:
 182     ungated!(ignore, Normal, template!(Word, NameValueStr: "reason")),
 183     ungated!(
 184         should_panic, Normal,
 185         template!(Word, List: r#"expected = "reason"#, NameValueStr: "reason"),
 186     ),
 187     // FIXME(Centril): This can be used on stable but shouldn't.
 188     ungated!(reexport_test_harness_main, Normal, template!(NameValueStr: "name")),
 189
 190     // Macros:
 191     ungated!(automatically_derived, Normal, template!(Word)),
 192     // FIXME(#14407)
 193     ungated!(macro_use, Normal, template!(Word, List: "name1, name2, ...")),
 194     ungated!(macro_escape, Normal, template!(Word)), // Deprecated synonym for `macro_use`.
 195     ungated!(macro_export, Normal, template!(Word, List: "local_inner_macros")),
 196     ungated!(proc_macro, Normal, template!(Word)),
 197     ungated!(
 198         proc_macro_derive, Normal,
 199         template!(List: "TraitName, /*opt*/ attributes(name1, name2, ...)"),
 200     ),
 201     ungated!(proc_macro_attribute, Normal, template!(Word)),
 202
 203     // Lints:
 204     ungated!(warn, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
 205     ungated!(allow, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
 206     ungated!(forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
 207     ungated!(deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
 208     ungated!(must_use, AssumedUsed, template!(Word, NameValueStr: "reason")),
 209     // FIXME(#14407)
 210     ungated!(
 211         deprecated, Normal,
 212         template!(
 213             Word,
 214             List: r#"/*opt*/ since = "version", /*opt*/ note = "reason""#,
 215             NameValueStr: "reason"
 216         ),
 217     ),
 218
 219     // Crate properties:
 220     ungated!(crate_name, CrateLevel, template!(NameValueStr: "name")),
 221     ungated!(crate_type, CrateLevel, template!(NameValueStr: "bin|lib|...")),
 222     ungated!(crate_id, CrateLevel, template!(NameValueStr: "ignored")),
 223
 224     // ABI, linking, symbols, and FFI
 225     ungated!(
 226         link, AssumedUsed,
 227         template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...", /*opt*/ wasm_import_module = "...""#),
 228     ),
 229     ungated!(link_name, AssumedUsed, template!(NameValueStr: "name")),
 230     ungated!(no_link, AssumedUsed, template!(Word)),
 231     ungated!(repr, AssumedUsed, template!(List: "C")),
 232     ungated!(export_name, AssumedUsed, template!(NameValueStr: "name")),
 233     ungated!(link_section, AssumedUsed, template!(NameValueStr: "name")),
 234     ungated!(no_mangle, AssumedUsed, template!(Word)),
 235     ungated!(used, AssumedUsed, template!(Word)),
 236
 237     // Limits:
 238     ungated!(recursion_limit, CrateLevel, template!(NameValueStr: "N")),
 239     ungated!(type_length_limit, CrateLevel, template!(NameValueStr: "N")),
 240     gated!(
 241         const_eval_limit, CrateLevel, template!(NameValueStr: "N"), const_eval_limit,
 242         experimental!(const_eval_limit)
 243     ),
 244     gated!(
 245         move_size_limit, CrateLevel, template!(NameValueStr: "N"), large_assignments,
 246         experimental!(move_size_limit)
 247     ),
 248
 249     // Entry point:
 250     ungated!(main, Normal, template!(Word)),
 251     ungated!(start, Normal, template!(Word)),
 252     ungated!(no_start, CrateLevel, template!(Word)),
 253     ungated!(no_main, CrateLevel, template!(Word)),
 254
 255     // Modules, prelude, and resolution:
 256     ungated!(path, Normal, template!(NameValueStr: "file")),
 257     ungated!(no_std, CrateLevel, template!(Word)),
 258     ungated!(no_implicit_prelude, Normal, template!(Word)),
 259     ungated!(non_exhaustive, AssumedUsed, template!(Word)),
 260
 261     // Runtime
 262     ungated!(windows_subsystem, AssumedUsed, template!(NameValueStr: "windows|console")),
 263     ungated!(panic_handler, Normal, template!(Word)), // RFC 2070
 264
 265     // Code generation:
 266     ungated!(inline, AssumedUsed, template!(Word, List: "always|never")),
 267     ungated!(cold, AssumedUsed, template!(Word)),
 268     ungated!(no_builtins, AssumedUsed, template!(Word)),
 269     ungated!(target_feature, AssumedUsed, template!(List: r#"enable = "name""#)),
 270     ungated!(track_caller, AssumedUsed, template!(Word)),
 271     gated!(
 272         no_sanitize, AssumedUsed,
 273         template!(List: "address, memory, thread"),
 274         experimental!(no_sanitize)
 275     ),
 276     gated!(no_coverage, AssumedUsed, template!(Word), experimental!(no_coverage)),
 277
 278     // FIXME: #14408 assume docs are used since rustdoc looks at them.
 279     ungated!(doc, AssumedUsed, template!(List: "hidden|inline|...", NameValueStr: "string")),
 280
 281     // ==========================================================================
 282     // Unstable attributes:
 283     // ==========================================================================
 284
 285     // Linking:
 286     gated!(naked, AssumedUsed, template!(Word), naked_functions, experimental!(naked)),
 287     gated!(
 288         link_ordinal, AssumedUsed, template!(List: "ordinal"), raw_dylib,
 289         experimental!(link_ordinal)
 290     ),
 291
 292     // Plugins:
 293     (
 294         sym::plugin_registrar, Normal, template!(Word),
 295         Gated(
 296             Stability::Deprecated(
 297                 "https://github.com/rust-lang/rust/pull/64675",
 298                 Some("may be removed in a future compiler version"),
 299             ),
 300             sym::plugin_registrar,
 301             "compiler plugins are deprecated",
 302             cfg_fn!(plugin_registrar)
 303         )
 304     ),
 305     (
 306         sym::plugin, CrateLevel, template!(List: "name"),
 307         Gated(
 308             Stability::Deprecated(
 309                 "https://github.com/rust-lang/rust/pull/64675",
 310                 Some("may be removed in a future compiler version"),
 311             ),
 312             sym::plugin,
 313             "compiler plugins are deprecated",
 314             cfg_fn!(plugin)
 315         )
 316     ),
 317
 318     // Testing:
 319     gated!(allow_fail, Normal, template!(Word), experimental!(allow_fail)),
 320     gated!(
 321         test_runner, CrateLevel, template!(List: "path"), custom_test_frameworks,
 322         "custom test frameworks are an unstable feature",
 323     ),
 324     // RFC #1268
 325     gated!(marker, AssumedUsed, template!(Word), marker_trait_attr, experimental!(marker)),
 326     gated!(
 327         thread_local, AssumedUsed, template!(Word),
 328         "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
 329     ),
 330     gated!(no_core, CrateLevel, template!(Word), experimental!(no_core)),
 331     // RFC 2412
 332     gated!(
 333         optimize, AssumedUsed, template!(List: "size|speed"), optimize_attribute,
 334         experimental!(optimize),
 335     ),
 336     // RFC 2867
 337     gated!(instruction_set, AssumedUsed, template!(List: "set"), isa_attribute, experimental!(instruction_set)),
 338
 339     gated!(ffi_returns_twice, AssumedUsed, template!(Word), experimental!(ffi_returns_twice)),
 340     gated!(ffi_pure, AssumedUsed, template!(Word), experimental!(ffi_pure)),
 341     gated!(ffi_const, AssumedUsed, template!(Word), experimental!(ffi_const)),
 342     gated!(
 343         register_attr, CrateLevel, template!(List: "attr1, attr2, ..."),
 344         experimental!(register_attr),
 345     ),
 346     gated!(
 347         register_tool, CrateLevel, template!(List: "tool1, tool2, ..."),
 348         experimental!(register_tool),
 349     ),
 350
 351     gated!(cmse_nonsecure_entry, AssumedUsed, template!(Word), experimental!(cmse_nonsecure_entry)),
 352
 353     // ==========================================================================
 354     // Internal attributes: Stability, deprecation, and unsafe:
 355     // ==========================================================================
 356
 357     ungated!(feature, CrateLevel, template!(List: "name1, name1, ...")),
 358     // FIXME(#14407) -- only looked at on-demand so we can't
 359     // guarantee they'll have already been checked.
 360     ungated!(
 361         rustc_deprecated, AssumedUsed,
 362         template!(List: r#"since = "version", reason = "...""#)
 363     ),
 364     // FIXME(#14407)
 365     ungated!(stable, AssumedUsed, template!(List: r#"feature = "name", since = "version""#)),
 366     // FIXME(#14407)
 367     ungated!(
 368         unstable, AssumedUsed,
 369         template!(List: r#"feature = "name", reason = "...", issue = "N""#),
 370     ),
 371     // FIXME(#14407)
 372     ungated!(rustc_const_unstable, AssumedUsed, template!(List: r#"feature = "name""#)),
 373     // FIXME(#14407)
 374     ungated!(rustc_const_stable, AssumedUsed, template!(List: r#"feature = "name""#)),
 375     gated!(
 376         allow_internal_unstable, AssumedUsed, template!(Word, List: "feat1, feat2, ..."),
 377         "allow_internal_unstable side-steps feature gating and stability checks",
 378     ),
 379     gated!(
 380         rustc_allow_const_fn_unstable, AssumedUsed, template!(Word, List: "feat1, feat2, ..."),
 381         "rustc_allow_const_fn_unstable side-steps feature gating and stability checks"
 382     ),
 383     gated!(
 384         allow_internal_unsafe, Normal, template!(Word),
 385         "allow_internal_unsafe side-steps the unsafe_code lint",
 386     ),
 387
 388     // ==========================================================================
 389     // Internal attributes: Type system related:
 390     // ==========================================================================
 391
 392     gated!(fundamental, AssumedUsed, template!(Word), experimental!(fundamental)),
 393     gated!(
 394         may_dangle, Normal, template!(Word), dropck_eyepatch,
 395         "`may_dangle` has unstable semantics and may be removed in the future",
 396     ),
 397
 398     // ==========================================================================
 399     // Internal attributes: Runtime related:
 400     // ==========================================================================
 401
 402     rustc_attr!(rustc_allocator, AssumedUsed, template!(Word), IMPL_DETAIL),
 403     rustc_attr!(rustc_allocator_nounwind, AssumedUsed, template!(Word), IMPL_DETAIL),
 404     gated!(alloc_error_handler, Normal, template!(Word), experimental!(alloc_error_handler)),
 405     gated!(
 406         default_lib_allocator, AssumedUsed, template!(Word), allocator_internals,
 407         experimental!(default_lib_allocator),
 408     ),
 409     gated!(
 410         needs_allocator, Normal, template!(Word), allocator_internals,
 411         experimental!(needs_allocator),
 412     ),
 413     gated!(panic_runtime, AssumedUsed, template!(Word), experimental!(panic_runtime)),
 414     gated!(needs_panic_runtime, AssumedUsed, template!(Word), experimental!(needs_panic_runtime)),
 415     gated!(
 416         unwind, AssumedUsed, template!(List: "allowed|aborts"), unwind_attributes,
 417         experimental!(unwind),
 418     ),
 419     gated!(
 420         compiler_builtins, AssumedUsed, template!(Word),
 421         "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
 422         which contains compiler-rt intrinsics and will never be stable",
 423     ),
 424     gated!(
 425         profiler_runtime, AssumedUsed, template!(Word),
 426         "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
 427         which contains the profiler runtime and will never be stable",
 428     ),
 429
 430     // ==========================================================================
 431     // Internal attributes, Linkage:
 432     // ==========================================================================
 433
 434     gated!(
 435         linkage, AssumedUsed, template!(NameValueStr: "external|internal|..."),
 436         "the `linkage` attribute is experimental and not portable across platforms",
 437     ),
 438     rustc_attr!(rustc_std_internal_symbol, AssumedUsed, template!(Word), INTERNAL_UNSTABLE),
 439
 440     // ==========================================================================
 441     // Internal attributes, Macro related:
 442     // ==========================================================================
 443
 444     rustc_attr!(rustc_builtin_macro, AssumedUsed, template!(Word, NameValueStr: "name"), IMPL_DETAIL),
 445     rustc_attr!(rustc_proc_macro_decls, Normal, template!(Word), INTERNAL_UNSTABLE),
 446     rustc_attr!(
 447         rustc_macro_transparency, AssumedUsed,
 448         template!(NameValueStr: "transparent|semitransparent|opaque"),
 449         "used internally for testing macro hygiene",
 450     ),
 451
 452     // ==========================================================================
 453     // Internal attributes, Diagnostics related:
 454     // ==========================================================================
 455
 456     rustc_attr!(
 457         rustc_on_unimplemented, AssumedUsed,
 458         template!(
 459             List: r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
 460             NameValueStr: "message"
 461         ),
 462         INTERNAL_UNSTABLE
 463     ),
 464     // Enumerates "identity-like" conversion methods to suggest on type mismatch.
 465     rustc_attr!(rustc_conversion_suggestion, AssumedUsed, template!(Word), INTERNAL_UNSTABLE),
 466
 467     // ==========================================================================
 468     // Internal attributes, Const related:
 469     // ==========================================================================
 470
 471     rustc_attr!(rustc_promotable, AssumedUsed, template!(Word), IMPL_DETAIL),
 472     rustc_attr!(rustc_args_required_const, AssumedUsed, template!(List: "N"), INTERNAL_UNSTABLE),
 473     rustc_attr!(rustc_legacy_const_generics, AssumedUsed, template!(List: "N"), INTERNAL_UNSTABLE),
 474
 475     // ==========================================================================
 476     // Internal attributes, Layout related:
 477     // ==========================================================================
 478
 479     rustc_attr!(
 480         rustc_layout_scalar_valid_range_start, AssumedUsed, template!(List: "value"),
 481         "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
 482         niche optimizations in libcore and will never be stable",
 483     ),
 484     rustc_attr!(
 485         rustc_layout_scalar_valid_range_end, AssumedUsed, template!(List: "value"),
 486         "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
 487         niche optimizations in libcore and will never be stable",
 488     ),
 489     rustc_attr!(
 490         rustc_nonnull_optimization_guaranteed, AssumedUsed, template!(Word),
 491         "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
 492         niche optimizations in libcore and will never be stable",
 493     ),
 494
 495     // ==========================================================================
 496     // Internal attributes, Misc:
 497     // ==========================================================================
 498     gated!(
 499         lang, Normal, template!(NameValueStr: "name"), lang_items,
 500         "language items are subject to change",
 501     ),
 502     (
 503         sym::rustc_diagnostic_item,
 504         Normal,
 505         template!(NameValueStr: "name"),
 506         Gated(
 507             Stability::Unstable,
 508             sym::rustc_attrs,
 509             "diagnostic items compiler internal support for linting",
 510             cfg_fn!(rustc_attrs),
 511         ),
 512     ),
 513     gated!(
 514         // Used in resolve:
 515         prelude_import, AssumedUsed, template!(Word),
 516         "`#[prelude_import]` is for use by rustc only",
 517     ),
 518     gated!(
 519         rustc_paren_sugar, Normal, template!(Word), unboxed_closures,
 520         "unboxed_closures are still evolving",
 521     ),
 522     rustc_attr!(
 523         rustc_inherit_overflow_checks, AssumedUsed, template!(Word),
 524         "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
 525         overflow checking behavior of several libcore functions that are inlined \
 526         across crates and will never be stable",
 527     ),
 528     rustc_attr!(rustc_reservation_impl, Normal, template!(NameValueStr: "reservation message"),
 529                 "the `#[rustc_reservation_impl]` attribute is internally used \
 530                  for reserving for `for<T> From<!> for T` impl"
 531     ),
 532     rustc_attr!(
 533         rustc_test_marker, Normal, template!(Word),
 534         "the `#[rustc_test_marker]` attribute is used internally to track tests",
 535     ),
 536     rustc_attr!(
 537         rustc_unsafe_specialization_marker, Normal, template!(Word),
 538         "the `#[rustc_unsafe_specialization_marker]` attribute is used to check specializations"
 539     ),
 540     rustc_attr!(
 541         rustc_specialization_trait, Normal, template!(Word),
 542         "the `#[rustc_specialization_trait]` attribute is used to check specializations"
 543     ),
 544     rustc_attr!(
 545         rustc_main, Normal, template!(Word),
 546         "the `#[rustc_main]` attribute is used internally to specify test entry point function",
 547     ),
 548     rustc_attr!(
 549         rustc_skip_array_during_method_dispatch, Normal, template!(Word),
 550         "the `#[rustc_skip_array_during_method_dispatch]` attribute is used to exclude a trait \
 551         from method dispatch when the receiver is an array, for compatibility in editions < 2021."
 552     ),
 553
 554     // ==========================================================================
 555     // Internal attributes, Testing:
 556     // ==========================================================================
 557
 558     rustc_attr!(TEST, rustc_outlives, Normal, template!(Word)),
 559     rustc_attr!(TEST, rustc_capture_analysis, Normal, template!(Word)),
 560     rustc_attr!(TEST, rustc_variance, Normal, template!(Word)),
 561     rustc_attr!(TEST, rustc_layout, Normal, template!(List: "field1, field2, ...")),
 562     rustc_attr!(TEST, rustc_regions, Normal, template!(Word)),
 563     rustc_attr!(
 564         TEST, rustc_error, AssumedUsed,
 565         template!(Word, List: "delay_span_bug_from_inside_query")
 566     ),
 567     rustc_attr!(TEST, rustc_dump_user_substs, AssumedUsed, template!(Word)),
 568     rustc_attr!(TEST, rustc_if_this_changed, AssumedUsed, template!(Word, List: "DepNode")),
 569     rustc_attr!(TEST, rustc_then_this_would_need, AssumedUsed, template!(List: "DepNode")),
 570     rustc_attr!(
 571         TEST, rustc_dirty, AssumedUsed,
 572         template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
 573     ),
 574     rustc_attr!(
 575         TEST, rustc_clean, AssumedUsed,
 576         template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
 577     ),
 578     rustc_attr!(
 579         TEST, rustc_partition_reused, AssumedUsed,
 580         template!(List: r#"cfg = "...", module = "...""#),
 581     ),
 582     rustc_attr!(
 583         TEST, rustc_partition_codegened, AssumedUsed,
 584         template!(List: r#"cfg = "...", module = "...""#),
 585     ),
 586     rustc_attr!(
 587         TEST, rustc_expected_cgu_reuse, AssumedUsed,
 588         template!(List: r#"cfg = "...", module = "...", kind = "...""#),
 589     ),
 590     rustc_attr!(TEST, rustc_synthetic, AssumedUsed, template!(Word)),
 591     rustc_attr!(TEST, rustc_symbol_name, AssumedUsed, template!(Word)),
 592     rustc_attr!(TEST, rustc_polymorphize_error, AssumedUsed, template!(Word)),
 593     rustc_attr!(TEST, rustc_def_path, AssumedUsed, template!(Word)),
 594     rustc_attr!(TEST, rustc_mir, AssumedUsed, template!(List: "arg1, arg2, ...")),
 595     rustc_attr!(TEST, rustc_dump_program_clauses, AssumedUsed, template!(Word)),
 596     rustc_attr!(TEST, rustc_dump_env_program_clauses, AssumedUsed, template!(Word)),
 597     rustc_attr!(TEST, rustc_object_lifetime_default, AssumedUsed, template!(Word)),
 598     rustc_attr!(TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/)),
 599     gated!(
 600         omit_gdb_pretty_printer_section, AssumedUsed, template!(Word),
 601         "the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
 602     ),
 603 ];
 604
 605 pub fn deprecated_attributes() -> Vec<&'static BuiltinAttribute> {
 606     BUILTIN_ATTRIBUTES.iter().filter(|(.., gate)| gate.is_deprecated()).collect()
 607 }
 608
 609 pub fn is_builtin_attr_name(name: Symbol) -> bool {
 610     BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
 611 }
 612
 613 pub static BUILTIN_ATTRIBUTE_MAP: SyncLazy<FxHashMap<Symbol, &BuiltinAttribute>> =
 614     SyncLazy::new(|| {
 615         let mut map = FxHashMap::default();
 616         for attr in BUILTIN_ATTRIBUTES.iter() {
 617             if map.insert(attr.0, attr).is_some() {
 618                 panic!("duplicate builtin attribute `{}`", attr.0);
 619             }
 620         }
 621         map
 622     });