rustc_feature/
builtin_attrs.rs

1//! Built-in attributes and `cfg` flag gating.
2
3use std::sync::LazyLock;
4
5use AttributeDuplicates::*;
6use AttributeGate::*;
7use AttributeType::*;
8use rustc_attr_data_structures::EncodeCrossCrate;
9use rustc_data_structures::fx::FxHashMap;
10use rustc_span::edition::Edition;
11use rustc_span::{Symbol, sym};
12
13use crate::Features;
14
15type GateFn = fn(&Features) -> bool;
16
17pub type GatedCfg = (Symbol, Symbol, GateFn);
18
19/// `cfg(...)`'s that are feature gated.
20const GATED_CFGS: &[GatedCfg] = &[
21    // (name in cfg, feature, function to check if the feature is enabled)
22    (sym::overflow_checks, sym::cfg_overflow_checks, Features::cfg_overflow_checks),
23    (sym::ub_checks, sym::cfg_ub_checks, Features::cfg_ub_checks),
24    (sym::contract_checks, sym::cfg_contract_checks, Features::cfg_contract_checks),
25    (sym::target_thread_local, sym::cfg_target_thread_local, Features::cfg_target_thread_local),
26    (
27        sym::target_has_atomic_equal_alignment,
28        sym::cfg_target_has_atomic_equal_alignment,
29        Features::cfg_target_has_atomic_equal_alignment,
30    ),
31    (
32        sym::target_has_atomic_load_store,
33        sym::cfg_target_has_atomic,
34        Features::cfg_target_has_atomic,
35    ),
36    (sym::sanitize, sym::cfg_sanitize, Features::cfg_sanitize),
37    (sym::version, sym::cfg_version, Features::cfg_version),
38    (sym::relocation_model, sym::cfg_relocation_model, Features::cfg_relocation_model),
39    (sym::sanitizer_cfi_generalize_pointers, sym::cfg_sanitizer_cfi, Features::cfg_sanitizer_cfi),
40    (sym::sanitizer_cfi_normalize_integers, sym::cfg_sanitizer_cfi, Features::cfg_sanitizer_cfi),
41    // this is consistent with naming of the compiler flag it's for
42    (sym::fmt_debug, sym::fmt_debug, Features::fmt_debug),
43    (sym::emscripten_wasm_eh, sym::cfg_emscripten_wasm_eh, Features::cfg_emscripten_wasm_eh),
44    (
45        sym::target_has_reliable_f16,
46        sym::cfg_target_has_reliable_f16_f128,
47        Features::cfg_target_has_reliable_f16_f128,
48    ),
49    (
50        sym::target_has_reliable_f16_math,
51        sym::cfg_target_has_reliable_f16_f128,
52        Features::cfg_target_has_reliable_f16_f128,
53    ),
54    (
55        sym::target_has_reliable_f128,
56        sym::cfg_target_has_reliable_f16_f128,
57        Features::cfg_target_has_reliable_f16_f128,
58    ),
59    (
60        sym::target_has_reliable_f128_math,
61        sym::cfg_target_has_reliable_f16_f128,
62        Features::cfg_target_has_reliable_f16_f128,
63    ),
64];
65
66/// Find a gated cfg determined by the `pred`icate which is given the cfg's name.
67pub fn find_gated_cfg(pred: impl Fn(Symbol) -> bool) -> Option<&'static GatedCfg> {
68    GATED_CFGS.iter().find(|(cfg_sym, ..)| pred(*cfg_sym))
69}
70
71// If you change this, please modify `src/doc/unstable-book` as well. You must
72// move that documentation into the relevant place in the other docs, and
73// remove the chapter on the flag.
74
75#[derive(Copy, Clone, PartialEq, Debug)]
76pub enum AttributeType {
77    /// Normal, builtin attribute that is consumed
78    /// by the compiler before the unused_attribute check
79    Normal,
80
81    /// Builtin attribute that is only allowed at the crate level
82    CrateLevel,
83}
84
85#[derive(Copy, Clone, PartialEq, Debug)]
86pub enum AttributeSafety {
87    /// Normal attribute that does not need `#[unsafe(...)]`
88    Normal,
89
90    /// Unsafe attribute that requires safety obligations to be discharged.
91    ///
92    /// An error is emitted when `#[unsafe(...)]` is omitted, except when the attribute's edition
93    /// is less than the one stored in `unsafe_since`. This handles attributes that were safe in
94    /// earlier editions, but become unsafe in later ones.
95    Unsafe { unsafe_since: Option<Edition> },
96}
97
98#[derive(Clone, Debug, Copy)]
99pub enum AttributeGate {
100    /// A gated attribute which requires a feature gate to be enabled.
101    Gated {
102        /// The feature gate, for example `#![feature(rustc_attrs)]` for rustc_* attributes.
103        feature: Symbol,
104        /// The error message displayed when an attempt is made to use the attribute without its feature gate.
105        message: &'static str,
106        /// Check function to be called during the `PostExpansionVisitor` pass.
107        check: fn(&Features) -> bool,
108        /// Notes to be displayed when an attempt is made to use the attribute without its feature gate.
109        notes: &'static [&'static str],
110    },
111    /// Ungated attribute, can be used on all release channels
112    Ungated,
113}
114
115// FIXME(jdonszelmann): move to rustc_attr_data_structures
116/// A template that the attribute input must match.
117/// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
118#[derive(Clone, Copy, Default)]
119pub struct AttributeTemplate {
120    /// If `true`, the attribute is allowed to be a bare word like `#[test]`.
121    pub word: bool,
122    /// If `Some`, the attribute is allowed to take a list of items like `#[allow(..)]`.
123    pub list: Option<&'static str>,
124    /// If non-empty, the attribute is allowed to take a list containing exactly
125    /// one of the listed words, like `#[coverage(off)]`.
126    pub one_of: &'static [Symbol],
127    /// If `Some`, the attribute is allowed to be a name/value pair where the
128    /// value is a string, like `#[must_use = "reason"]`.
129    pub name_value_str: Option<&'static str>,
130}
131
132impl AttributeTemplate {
133    pub fn suggestions(&self, inner: bool, name: impl std::fmt::Display) -> Vec<String> {
134        let mut suggestions = vec![];
135        let inner = if inner { "!" } else { "" };
136        if self.word {
137            suggestions.push(format!("#{inner}[{name}]"));
138        }
139        if let Some(descr) = self.list {
140            suggestions.push(format!("#{inner}[{name}({descr})]"));
141        }
142        suggestions.extend(self.one_of.iter().map(|&word| format!("#{inner}[{name}({word})]")));
143        if let Some(descr) = self.name_value_str {
144            suggestions.push(format!("#{inner}[{name} = \"{descr}\"]"));
145        }
146        suggestions.sort();
147
148        suggestions
149    }
150}
151
152/// How to handle multiple duplicate attributes on the same item.
153#[derive(Clone, Copy, Default)]
154pub enum AttributeDuplicates {
155    /// Duplicates of this attribute are allowed.
156    ///
157    /// This should only be used with attributes where duplicates have semantic
158    /// meaning, or some kind of "additive" behavior. For example, `#[warn(..)]`
159    /// can be specified multiple times, and it combines all the entries. Or use
160    /// this if there is validation done elsewhere.
161    #[default]
162    DuplicatesOk,
163    /// Duplicates after the first attribute will be an unused_attribute warning.
164    ///
165    /// This is usually used for "word" attributes, where they are used as a
166    /// boolean marker, like `#[used]`. It is not necessarily wrong that there
167    /// are duplicates, but the others should probably be removed.
168    WarnFollowing,
169    /// Same as `WarnFollowing`, but only issues warnings for word-style attributes.
170    ///
171    /// This is only for special cases, for example multiple `#[macro_use]` can
172    /// be warned, but multiple `#[macro_use(...)]` should not because the list
173    /// form has different meaning from the word form.
174    WarnFollowingWordOnly,
175    /// Duplicates after the first attribute will be an error.
176    ///
177    /// This should be used where duplicates would be ignored, but carry extra
178    /// meaning that could cause confusion. For example, `#[stable(since="1.0")]
179    /// #[stable(since="2.0")]`, which version should be used for `stable`?
180    ErrorFollowing,
181    /// Duplicates preceding the last instance of the attribute will be an error.
182    ///
183    /// This is the same as `ErrorFollowing`, except the last attribute is the
184    /// one that is "used". This is typically used in cases like codegen
185    /// attributes which usually only honor the last attribute.
186    ErrorPreceding,
187    /// Duplicates after the first attribute will be an unused_attribute warning
188    /// with a note that this will be an error in the future.
189    ///
190    /// This should be used for attributes that should be `ErrorFollowing`, but
191    /// because older versions of rustc silently accepted (and ignored) the
192    /// attributes, this is used to transition.
193    FutureWarnFollowing,
194    /// Duplicates preceding the last instance of the attribute will be a
195    /// warning, with a note that this will be an error in the future.
196    ///
197    /// This is the same as `FutureWarnFollowing`, except the last attribute is
198    /// the one that is "used". Ideally these can eventually migrate to
199    /// `ErrorPreceding`.
200    FutureWarnPreceding,
201}
202
203/// A convenience macro for constructing attribute templates.
204/// E.g., `template!(Word, List: "description")` means that the attribute
205/// supports forms `#[attr]` and `#[attr(description)]`.
206#[macro_export]
207macro_rules! template {
208    (Word) => { $crate::template!(@ true, None, &[], None) };
209    (List: $descr: expr) => { $crate::template!(@ false, Some($descr), &[], None) };
210    (OneOf: $one_of: expr) => { $crate::template!(@ false, None, $one_of, None) };
211    (NameValueStr: $descr: expr) => { $crate::template!(@ false, None, &[], Some($descr)) };
212    (Word, List: $descr: expr) => { $crate::template!(@ true, Some($descr), &[], None) };
213    (Word, NameValueStr: $descr: expr) => { $crate::template!(@ true, None, &[], Some($descr)) };
214    (List: $descr1: expr, NameValueStr: $descr2: expr) => {
215        $crate::template!(@ false, Some($descr1), &[], Some($descr2))
216    };
217    (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
218        $crate::template!(@ true, Some($descr1), &[], Some($descr2))
219    };
220    (@ $word: expr, $list: expr, $one_of: expr, $name_value_str: expr) => { $crate::AttributeTemplate {
221        word: $word, list: $list, one_of: $one_of, name_value_str: $name_value_str
222    } };
223}
224
225macro_rules! ungated {
226    (unsafe($edition:ident) $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr $(,)?) => {
227        BuiltinAttribute {
228            name: sym::$attr,
229            encode_cross_crate: $encode_cross_crate,
230            type_: $typ,
231            safety: AttributeSafety::Unsafe { unsafe_since: Some(Edition::$edition) },
232            template: $tpl,
233            gate: Ungated,
234            duplicates: $duplicates,
235        }
236    };
237    (unsafe $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr $(,)?) => {
238        BuiltinAttribute {
239            name: sym::$attr,
240            encode_cross_crate: $encode_cross_crate,
241            type_: $typ,
242            safety: AttributeSafety::Unsafe { unsafe_since: None },
243            template: $tpl,
244            gate: Ungated,
245            duplicates: $duplicates,
246        }
247    };
248    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr $(,)?) => {
249        BuiltinAttribute {
250            name: sym::$attr,
251            encode_cross_crate: $encode_cross_crate,
252            type_: $typ,
253            safety: AttributeSafety::Normal,
254            template: $tpl,
255            gate: Ungated,
256            duplicates: $duplicates,
257        }
258    };
259}
260
261macro_rules! gated {
262    (unsafe $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $gate:ident, $message:expr $(,)?) => {
263        BuiltinAttribute {
264            name: sym::$attr,
265            encode_cross_crate: $encode_cross_crate,
266            type_: $typ,
267            safety: AttributeSafety::Unsafe { unsafe_since: None },
268            template: $tpl,
269            duplicates: $duplicates,
270            gate: Gated {
271                feature: sym::$gate,
272                message: $message,
273                check: Features::$gate,
274                notes: &[],
275            },
276        }
277    };
278    (unsafe $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $message:expr $(,)?) => {
279        BuiltinAttribute {
280            name: sym::$attr,
281            encode_cross_crate: $encode_cross_crate,
282            type_: $typ,
283            safety: AttributeSafety::Unsafe { unsafe_since: None },
284            template: $tpl,
285            duplicates: $duplicates,
286            gate: Gated {
287                feature: sym::$attr,
288                message: $message,
289                check: Features::$attr,
290                notes: &[],
291            },
292        }
293    };
294    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $gate:ident, $message:expr $(,)?) => {
295        BuiltinAttribute {
296            name: sym::$attr,
297            encode_cross_crate: $encode_cross_crate,
298            type_: $typ,
299            safety: AttributeSafety::Normal,
300            template: $tpl,
301            duplicates: $duplicates,
302            gate: Gated {
303                feature: sym::$gate,
304                message: $message,
305                check: Features::$gate,
306                notes: &[],
307            },
308        }
309    };
310    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $message:expr $(,)?) => {
311        BuiltinAttribute {
312            name: sym::$attr,
313            encode_cross_crate: $encode_cross_crate,
314            type_: $typ,
315            safety: AttributeSafety::Normal,
316            template: $tpl,
317            duplicates: $duplicates,
318            gate: Gated {
319                feature: sym::$attr,
320                message: $message,
321                check: Features::$attr,
322                notes: &[],
323            },
324        }
325    };
326}
327
328macro_rules! rustc_attr {
329    (TEST, $attr:ident, $typ:expr, $tpl:expr, $duplicate:expr, $encode_cross_crate:expr $(,)?) => {
330        rustc_attr!(
331            $attr,
332            $typ,
333            $tpl,
334            $duplicate,
335            $encode_cross_crate,
336            concat!(
337                "the `#[",
338                stringify!($attr),
339                "]` attribute is used for rustc unit tests"
340            ),
341        )
342    };
343    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $($notes:expr),* $(,)?) => {
344        BuiltinAttribute {
345            name: sym::$attr,
346            encode_cross_crate: $encode_cross_crate,
347            type_: $typ,
348            safety: AttributeSafety::Normal,
349            template: $tpl,
350            duplicates: $duplicates,
351            gate: Gated {
352                feature: sym::rustc_attrs,
353                message: "use of an internal attribute",
354                check: Features::rustc_attrs,
355                notes: &[
356                    concat!("the `#[",
357                    stringify!($attr),
358                    "]` attribute is an internal implementation detail that will never be stable"),
359                    $($notes),*
360                    ]
361            },
362        }
363    };
364}
365
366macro_rules! experimental {
367    ($attr:ident) => {
368        concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
369    };
370}
371
372pub struct BuiltinAttribute {
373    pub name: Symbol,
374    /// Whether this attribute is encode cross crate.
375    ///
376    /// If so, it is encoded in the crate metadata.
377    /// Otherwise, it can only be used in the local crate.
378    pub encode_cross_crate: EncodeCrossCrate,
379    pub type_: AttributeType,
380    pub safety: AttributeSafety,
381    pub template: AttributeTemplate,
382    pub duplicates: AttributeDuplicates,
383    pub gate: AttributeGate,
384}
385
386/// Attributes that have a special meaning to rustc or rustdoc.
387#[rustfmt::skip]
388pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
389    // ==========================================================================
390    // Stable attributes:
391    // ==========================================================================
392
393    // Conditional compilation:
394    ungated!(cfg, Normal, template!(List: "predicate"), DuplicatesOk, EncodeCrossCrate::Yes),
395    ungated!(cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ..."), DuplicatesOk, EncodeCrossCrate::Yes),
396
397    // Testing:
398    ungated!(
399        ignore, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing,
400        EncodeCrossCrate::No,
401    ),
402    ungated!(
403        should_panic, Normal,
404        template!(Word, List: r#"expected = "reason""#, NameValueStr: "reason"), FutureWarnFollowing,
405        EncodeCrossCrate::No,
406    ),
407    // FIXME(Centril): This can be used on stable but shouldn't.
408    ungated!(
409        reexport_test_harness_main, CrateLevel, template!(NameValueStr: "name"), ErrorFollowing,
410        EncodeCrossCrate::No,
411    ),
412
413    // Macros:
414    ungated!(automatically_derived, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
415    ungated!(
416        macro_use, Normal, template!(Word, List: "name1, name2, ..."), WarnFollowingWordOnly,
417        EncodeCrossCrate::No,
418    ),
419    ungated!(macro_escape, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No), // Deprecated synonym for `macro_use`.
420    ungated!(
421        macro_export, Normal, template!(Word, List: "local_inner_macros"),
422        WarnFollowing, EncodeCrossCrate::Yes
423    ),
424    ungated!(proc_macro, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::No),
425    ungated!(
426        proc_macro_derive, Normal, template!(List: "TraitName, /*opt*/ attributes(name1, name2, ...)"),
427        ErrorFollowing, EncodeCrossCrate::No,
428    ),
429    ungated!(proc_macro_attribute, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::No),
430
431    // Lints:
432    ungated!(
433        warn, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
434        DuplicatesOk, EncodeCrossCrate::No,
435    ),
436    ungated!(
437        allow, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
438        DuplicatesOk, EncodeCrossCrate::No,
439    ),
440    ungated!(
441        expect, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
442        DuplicatesOk, EncodeCrossCrate::No,
443    ),
444    ungated!(
445        forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
446        DuplicatesOk, EncodeCrossCrate::No
447    ),
448    ungated!(
449        deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
450        DuplicatesOk, EncodeCrossCrate::No
451    ),
452    ungated!(
453        must_use, Normal, template!(Word, NameValueStr: "reason"),
454        FutureWarnFollowing, EncodeCrossCrate::Yes
455    ),
456    gated!(
457        must_not_suspend, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing,
458        EncodeCrossCrate::Yes, experimental!(must_not_suspend)
459    ),
460    ungated!(
461        deprecated, Normal,
462        template!(
463            Word,
464            List: r#"/*opt*/ since = "version", /*opt*/ note = "reason""#,
465            NameValueStr: "reason"
466        ),
467        ErrorFollowing, EncodeCrossCrate::Yes
468    ),
469
470    // Crate properties:
471    ungated!(
472        crate_name, CrateLevel, template!(NameValueStr: "name"), FutureWarnFollowing,
473        EncodeCrossCrate::No,
474    ),
475    ungated!(
476        crate_type, CrateLevel, template!(NameValueStr: "bin|lib|..."), DuplicatesOk,
477        EncodeCrossCrate::No,
478    ),
479
480    // ABI, linking, symbols, and FFI
481    ungated!(
482        link, Normal,
483        template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...", /*opt*/ wasm_import_module = "...", /*opt*/ import_name_type = "decorated|noprefix|undecorated""#),
484        DuplicatesOk,
485        EncodeCrossCrate::No,
486    ),
487    ungated!(
488        link_name, Normal, template!(NameValueStr: "name"),
489        FutureWarnPreceding, EncodeCrossCrate::Yes
490    ),
491    ungated!(no_link, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
492    ungated!(repr, Normal, template!(List: "C"), DuplicatesOk, EncodeCrossCrate::No),
493    gated!(align, Normal, template!(List: "alignment"), DuplicatesOk, EncodeCrossCrate::No, fn_align, experimental!(align)),
494    ungated!(unsafe(Edition2024) export_name, Normal, template!(NameValueStr: "name"), FutureWarnPreceding, EncodeCrossCrate::No),
495    ungated!(unsafe(Edition2024) link_section, Normal, template!(NameValueStr: "name"), FutureWarnPreceding, EncodeCrossCrate::No),
496    ungated!(unsafe(Edition2024) no_mangle, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
497    ungated!(used, Normal, template!(Word, List: "compiler|linker"), WarnFollowing, EncodeCrossCrate::No),
498    ungated!(link_ordinal, Normal, template!(List: "ordinal"), ErrorPreceding, EncodeCrossCrate::Yes),
499    ungated!(unsafe naked, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
500
501    // Limits:
502    ungated!(
503        recursion_limit, CrateLevel, template!(NameValueStr: "N"), FutureWarnFollowing,
504        EncodeCrossCrate::No
505    ),
506    ungated!(
507        type_length_limit, CrateLevel, template!(NameValueStr: "N"), FutureWarnFollowing,
508        EncodeCrossCrate::No
509    ),
510    gated!(
511        move_size_limit, CrateLevel, template!(NameValueStr: "N"), ErrorFollowing,
512        EncodeCrossCrate::No, large_assignments, experimental!(move_size_limit)
513    ),
514
515    // Entry point:
516    ungated!(no_main, CrateLevel, template!(Word), WarnFollowing, EncodeCrossCrate::No),
517
518    // Modules, prelude, and resolution:
519    ungated!(path, Normal, template!(NameValueStr: "file"), FutureWarnFollowing, EncodeCrossCrate::No),
520    ungated!(no_std, CrateLevel, template!(Word), WarnFollowing, EncodeCrossCrate::No),
521    ungated!(no_implicit_prelude, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
522    ungated!(non_exhaustive, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
523
524    // Runtime
525    ungated!(
526        windows_subsystem, CrateLevel,
527        template!(NameValueStr: "windows|console"), FutureWarnFollowing,
528        EncodeCrossCrate::No
529    ),
530    ungated!(panic_handler, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes), // RFC 2070
531
532    // Code generation:
533    ungated!(inline, Normal, template!(Word, List: "always|never"), FutureWarnFollowing, EncodeCrossCrate::No),
534    ungated!(cold, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
535    ungated!(no_builtins, CrateLevel, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
536    ungated!(
537        target_feature, Normal, template!(List: r#"enable = "name""#),
538        DuplicatesOk, EncodeCrossCrate::No,
539    ),
540    ungated!(track_caller, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
541    ungated!(instruction_set, Normal, template!(List: "set"), ErrorPreceding, EncodeCrossCrate::No),
542    gated!(
543        no_sanitize, Normal,
544        template!(List: "address, kcfi, memory, thread"), DuplicatesOk,
545        EncodeCrossCrate::No, experimental!(no_sanitize)
546    ),
547    gated!(
548        coverage, Normal, template!(OneOf: &[sym::off, sym::on]),
549        ErrorPreceding, EncodeCrossCrate::No,
550        coverage_attribute, experimental!(coverage)
551    ),
552
553    ungated!(
554        doc, Normal, template!(List: "hidden|inline|...", NameValueStr: "string"), DuplicatesOk,
555        EncodeCrossCrate::Yes
556    ),
557
558    // Debugging
559    ungated!(
560        debugger_visualizer, Normal,
561        template!(List: r#"natvis_file = "...", gdb_script_file = "...""#),
562        DuplicatesOk, EncodeCrossCrate::No
563    ),
564    ungated!(collapse_debuginfo, Normal, template!(List: "no|external|yes"), ErrorFollowing,
565        EncodeCrossCrate::Yes
566    ),
567
568    // ==========================================================================
569    // Unstable attributes:
570    // ==========================================================================
571
572    // Linking:
573    gated!(
574        export_stable, Normal, template!(Word), WarnFollowing,
575        EncodeCrossCrate::No, experimental!(export_stable)
576    ),
577
578    // Testing:
579    gated!(
580        test_runner, CrateLevel, template!(List: "path"), ErrorFollowing,
581        EncodeCrossCrate::Yes, custom_test_frameworks,
582        "custom test frameworks are an unstable feature",
583    ),
584    // RFC #1268
585    gated!(
586        marker, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
587        marker_trait_attr, experimental!(marker)
588    ),
589    gated!(
590        thread_local, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
591        "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
592    ),
593    gated!(
594        no_core, CrateLevel, template!(Word), WarnFollowing,
595        EncodeCrossCrate::No, experimental!(no_core)
596    ),
597    // RFC 2412
598    gated!(
599        optimize, Normal, template!(List: "none|size|speed"), ErrorPreceding,
600        EncodeCrossCrate::No, optimize_attribute, experimental!(optimize)
601    ),
602
603    gated!(
604        unsafe ffi_pure, Normal, template!(Word), WarnFollowing,
605        EncodeCrossCrate::No, experimental!(ffi_pure)
606    ),
607    gated!(
608        unsafe ffi_const, Normal, template!(Word), WarnFollowing,
609        EncodeCrossCrate::No, experimental!(ffi_const)
610    ),
611    gated!(
612        register_tool, CrateLevel, template!(List: "tool1, tool2, ..."), DuplicatesOk,
613        EncodeCrossCrate::No, experimental!(register_tool),
614    ),
615
616    // RFC 2632
617    // FIXME(const_trait_impl) remove this
618    gated!(
619        const_trait, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No, const_trait_impl,
620        "`const_trait` is a temporary placeholder for marking a trait that is suitable for `const` \
621        `impls` and all default bodies as `const`, which may be removed or renamed in the \
622        future."
623    ),
624    // lang-team MCP 147
625    gated!(
626        deprecated_safe, Normal, template!(List: r#"since = "version", note = "...""#), ErrorFollowing,
627        EncodeCrossCrate::Yes, experimental!(deprecated_safe),
628    ),
629
630    // `#[cfi_encoding = ""]`
631    gated!(
632        cfi_encoding, Normal, template!(NameValueStr: "encoding"), ErrorPreceding,
633        EncodeCrossCrate::Yes, experimental!(cfi_encoding)
634    ),
635
636    // `#[coroutine]` attribute to be applied to closures to make them coroutines instead
637    gated!(
638        coroutine, Normal, template!(Word), ErrorFollowing,
639        EncodeCrossCrate::No, coroutines, experimental!(coroutine)
640    ),
641
642    // RFC 3543
643    // `#[patchable_function_entry(prefix_nops = m, entry_nops = n)]`
644    gated!(
645        patchable_function_entry, Normal, template!(List: "prefix_nops = m, entry_nops = n"), ErrorPreceding,
646        EncodeCrossCrate::Yes, experimental!(patchable_function_entry)
647    ),
648
649    // Probably temporary component of min_generic_const_args.
650    // `#[type_const] const ASSOC: usize;`
651    gated!(
652        type_const, Normal, template!(Word), ErrorFollowing,
653        EncodeCrossCrate::Yes, min_generic_const_args, experimental!(type_const),
654    ),
655
656    // The `#[loop_match]` and `#[const_continue]` attributes are part of the
657    // lang experiment for RFC 3720 tracked in:
658    //
659    // - https://github.com/rust-lang/rust/issues/132306
660    gated!(
661        const_continue, Normal, template!(Word), ErrorFollowing,
662        EncodeCrossCrate::No, loop_match, experimental!(const_continue)
663    ),
664    gated!(
665        loop_match, Normal, template!(Word), ErrorFollowing,
666        EncodeCrossCrate::No, loop_match, experimental!(loop_match)
667    ),
668
669    // ==========================================================================
670    // Internal attributes: Stability, deprecation, and unsafe:
671    // ==========================================================================
672
673    ungated!(
674        feature, CrateLevel,
675        template!(List: "name1, name2, ..."), DuplicatesOk, EncodeCrossCrate::No,
676    ),
677    // DuplicatesOk since it has its own validation
678    ungated!(
679        stable, Normal,
680        template!(List: r#"feature = "name", since = "version""#), DuplicatesOk, EncodeCrossCrate::No,
681    ),
682    ungated!(
683        unstable, Normal,
684        template!(List: r#"feature = "name", reason = "...", issue = "N""#), DuplicatesOk,
685        EncodeCrossCrate::Yes
686    ),
687    ungated!(
688        unstable_feature_bound, Normal, template!(Word, List: "feat1, feat2, ..."),
689        DuplicatesOk, EncodeCrossCrate::No,
690    ),
691    ungated!(
692        rustc_const_unstable, Normal, template!(List: r#"feature = "name""#),
693        DuplicatesOk, EncodeCrossCrate::Yes
694    ),
695    ungated!(
696        rustc_const_stable, Normal,
697        template!(List: r#"feature = "name""#), DuplicatesOk, EncodeCrossCrate::No,
698    ),
699    ungated!(
700        rustc_default_body_unstable, Normal,
701        template!(List: r#"feature = "name", reason = "...", issue = "N""#),
702        DuplicatesOk, EncodeCrossCrate::No
703    ),
704    gated!(
705        allow_internal_unstable, Normal, template!(Word, List: "feat1, feat2, ..."),
706        DuplicatesOk, EncodeCrossCrate::Yes,
707        "allow_internal_unstable side-steps feature gating and stability checks",
708    ),
709    gated!(
710        allow_internal_unsafe, Normal, template!(Word), WarnFollowing,
711        EncodeCrossCrate::No, "allow_internal_unsafe side-steps the unsafe_code lint",
712    ),
713    rustc_attr!(
714        rustc_allowed_through_unstable_modules, Normal, template!(NameValueStr: "deprecation message"),
715        WarnFollowing, EncodeCrossCrate::No,
716        "rustc_allowed_through_unstable_modules special cases accidental stabilizations of stable items \
717        through unstable paths"
718    ),
719    rustc_attr!(
720        rustc_deprecated_safe_2024, Normal, template!(List: r#"audit_that = "...""#),
721        ErrorFollowing, EncodeCrossCrate::Yes,
722        "`#[rustc_deprecated_safe_2024]` is used to declare functions unsafe across the edition 2024 boundary",
723    ),
724    rustc_attr!(
725        rustc_pub_transparent, Normal, template!(Word),
726        ErrorFollowing, EncodeCrossCrate::Yes,
727        "used internally to mark types with a `transparent` representation when it is guaranteed by the documentation",
728    ),
729
730
731    // ==========================================================================
732    // Internal attributes: Type system related:
733    // ==========================================================================
734
735    gated!(fundamental, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes, experimental!(fundamental)),
736    gated!(
737        may_dangle, Normal, template!(Word), WarnFollowing,
738        EncodeCrossCrate::No, dropck_eyepatch,
739        "`may_dangle` has unstable semantics and may be removed in the future",
740    ),
741
742    rustc_attr!(
743        rustc_never_type_options,
744        Normal,
745        template!(List: r#"/*opt*/ fallback = "unit|niko|never|no""#),
746        ErrorFollowing,
747        EncodeCrossCrate::No,
748        "`rustc_never_type_options` is used to experiment with never type fallback and work on \
749         never type stabilization"
750    ),
751
752    // ==========================================================================
753    // Internal attributes: Runtime related:
754    // ==========================================================================
755
756    rustc_attr!(
757        rustc_allocator, Normal, template!(Word), WarnFollowing,
758        EncodeCrossCrate::No,
759    ),
760    rustc_attr!(
761        rustc_nounwind, Normal, template!(Word), WarnFollowing,
762        EncodeCrossCrate::No,
763    ),
764    rustc_attr!(
765        rustc_reallocator, Normal, template!(Word), WarnFollowing,
766        EncodeCrossCrate::No,
767    ),
768    rustc_attr!(
769        rustc_deallocator, Normal, template!(Word), WarnFollowing,
770        EncodeCrossCrate::No,
771    ),
772    rustc_attr!(
773        rustc_allocator_zeroed, Normal, template!(Word), WarnFollowing,
774        EncodeCrossCrate::No,
775    ),
776    gated!(
777        default_lib_allocator, Normal, template!(Word), WarnFollowing,
778        EncodeCrossCrate::No, allocator_internals, experimental!(default_lib_allocator),
779    ),
780    gated!(
781        needs_allocator, Normal, template!(Word), WarnFollowing,
782        EncodeCrossCrate::No, allocator_internals, experimental!(needs_allocator),
783    ),
784    gated!(
785        panic_runtime, CrateLevel, template!(Word), WarnFollowing,
786        EncodeCrossCrate::No, experimental!(panic_runtime)
787    ),
788    gated!(
789        needs_panic_runtime, CrateLevel, template!(Word), WarnFollowing,
790        EncodeCrossCrate::No, experimental!(needs_panic_runtime)
791    ),
792    gated!(
793        compiler_builtins, CrateLevel, template!(Word), WarnFollowing,
794        EncodeCrossCrate::No,
795        "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
796        which contains compiler-rt intrinsics and will never be stable",
797    ),
798    gated!(
799        profiler_runtime, CrateLevel, template!(Word), WarnFollowing,
800        EncodeCrossCrate::No,
801        "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
802        which contains the profiler runtime and will never be stable",
803    ),
804
805    // ==========================================================================
806    // Internal attributes, Linkage:
807    // ==========================================================================
808
809    gated!(
810        linkage, Normal, template!(NameValueStr: "external|internal|..."),
811        ErrorPreceding, EncodeCrossCrate::No,
812        "the `linkage` attribute is experimental and not portable across platforms",
813    ),
814    rustc_attr!(
815        rustc_std_internal_symbol, Normal, template!(Word), WarnFollowing,
816        EncodeCrossCrate::No,
817    ),
818
819    // ==========================================================================
820    // Internal attributes, Macro related:
821    // ==========================================================================
822
823    rustc_attr!(
824        rustc_builtin_macro, Normal,
825        template!(Word, List: "name, /*opt*/ attributes(name1, name2, ...)"), ErrorFollowing,
826        EncodeCrossCrate::Yes,
827    ),
828    rustc_attr!(
829        rustc_proc_macro_decls, Normal, template!(Word), WarnFollowing,
830        EncodeCrossCrate::No,
831    ),
832    rustc_attr!(
833        rustc_macro_transparency, Normal,
834        template!(NameValueStr: "transparent|semiopaque|opaque"), ErrorFollowing,
835        EncodeCrossCrate::Yes, "used internally for testing macro hygiene",
836    ),
837    rustc_attr!(
838        rustc_autodiff, Normal,
839        template!(Word, List: r#""...""#), DuplicatesOk,
840        EncodeCrossCrate::Yes,
841    ),
842    // Traces that are left when `cfg` and `cfg_attr` attributes are expanded.
843    // The attributes are not gated, to avoid stability errors, but they cannot be used in stable
844    // or unstable code directly because `sym::cfg_(attr_)trace` are not valid identifiers, they
845    // can only be generated by the compiler.
846    ungated!(
847        cfg_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
848        EncodeCrossCrate::No
849    ),
850    ungated!(
851        cfg_attr_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
852        EncodeCrossCrate::No
853    ),
854
855    // ==========================================================================
856    // Internal attributes, Diagnostics related:
857    // ==========================================================================
858
859    rustc_attr!(
860        rustc_on_unimplemented, Normal,
861        template!(
862            List: r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
863            NameValueStr: "message"
864        ),
865        ErrorFollowing, EncodeCrossCrate::Yes,
866        "see `#[diagnostic::on_unimplemented]` for the stable equivalent of this attribute"
867    ),
868    rustc_attr!(
869        rustc_confusables, Normal,
870        template!(List: r#""name1", "name2", ..."#),
871        ErrorFollowing, EncodeCrossCrate::Yes,
872    ),
873    // Enumerates "identity-like" conversion methods to suggest on type mismatch.
874    rustc_attr!(
875        rustc_conversion_suggestion, Normal, template!(Word),
876        WarnFollowing, EncodeCrossCrate::Yes,
877    ),
878    // Prevents field reads in the marked trait or method to be considered
879    // during dead code analysis.
880    rustc_attr!(
881        rustc_trivial_field_reads, Normal, template!(Word),
882        WarnFollowing, EncodeCrossCrate::Yes,
883    ),
884    // Used by the `rustc::potential_query_instability` lint to warn methods which
885    // might not be stable during incremental compilation.
886    rustc_attr!(
887        rustc_lint_query_instability, Normal, template!(Word),
888        WarnFollowing, EncodeCrossCrate::Yes,
889    ),
890    // Used by the `rustc::untracked_query_information` lint to warn methods which
891    // might not be stable during incremental compilation.
892    rustc_attr!(
893        rustc_lint_untracked_query_information, Normal, template!(Word),
894        WarnFollowing, EncodeCrossCrate::Yes,
895    ),
896    // Used by the `rustc::diagnostic_outside_of_impl` lints to assist in changes to diagnostic
897    // APIs. Any function with this attribute will be checked by that lint.
898    rustc_attr!(
899        rustc_lint_diagnostics, Normal, template!(Word),
900        WarnFollowing, EncodeCrossCrate::Yes,
901    ),
902    // Used by the `rustc::bad_opt_access` lint to identify `DebuggingOptions` and `CodegenOptions`
903    // types (as well as any others in future).
904    rustc_attr!(
905        rustc_lint_opt_ty, Normal, template!(Word),
906        WarnFollowing, EncodeCrossCrate::Yes,
907    ),
908    // Used by the `rustc::bad_opt_access` lint on fields
909    // types (as well as any others in future).
910    rustc_attr!(
911        rustc_lint_opt_deny_field_access, Normal, template!(List: "message"),
912        WarnFollowing, EncodeCrossCrate::Yes,
913    ),
914
915    // ==========================================================================
916    // Internal attributes, Const related:
917    // ==========================================================================
918
919    rustc_attr!(
920        rustc_promotable, Normal, template!(Word), WarnFollowing,
921        EncodeCrossCrate::No, ),
922    rustc_attr!(
923        rustc_legacy_const_generics, Normal, template!(List: "N"), ErrorFollowing,
924        EncodeCrossCrate::Yes,
925    ),
926    // Do not const-check this function's body. It will always get replaced during CTFE via `hook_special_const_fn`.
927    rustc_attr!(
928        rustc_do_not_const_check, Normal, template!(Word), WarnFollowing,
929        EncodeCrossCrate::Yes, "`#[rustc_do_not_const_check]` skips const-check for this function's body",
930    ),
931    rustc_attr!(
932        rustc_const_panic_str, Normal, template!(Word), WarnFollowing,
933        EncodeCrossCrate::Yes, "`#[rustc_const_panic_str]` ensures the argument to this function is &&str during const-check",
934    ),
935    rustc_attr!(
936        rustc_const_stable_indirect, Normal,
937        template!(Word),
938        WarnFollowing,
939        EncodeCrossCrate::No,
940        "this is an internal implementation detail",
941    ),
942    rustc_attr!(
943        rustc_intrinsic_const_stable_indirect, Normal,
944        template!(Word), WarnFollowing, EncodeCrossCrate::No,  "this is an internal implementation detail",
945    ),
946    gated!(
947        rustc_allow_const_fn_unstable, Normal,
948        template!(Word, List: "feat1, feat2, ..."), DuplicatesOk, EncodeCrossCrate::No,
949        "rustc_allow_const_fn_unstable side-steps feature gating and stability checks"
950    ),
951
952    // ==========================================================================
953    // Internal attributes, Layout related:
954    // ==========================================================================
955
956    rustc_attr!(
957        rustc_layout_scalar_valid_range_start, Normal, template!(List: "value"), ErrorFollowing,
958        EncodeCrossCrate::Yes,
959        "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
960        niche optimizations in the standard library",
961    ),
962    rustc_attr!(
963        rustc_layout_scalar_valid_range_end, Normal, template!(List: "value"), ErrorFollowing,
964        EncodeCrossCrate::Yes,
965        "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
966        niche optimizations in the standard library",
967    ),
968    rustc_attr!(
969        rustc_nonnull_optimization_guaranteed, Normal, template!(Word), WarnFollowing,
970        EncodeCrossCrate::Yes,
971        "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document \
972        guaranteed niche optimizations in the standard library",
973        "the compiler does not even check whether the type indeed is being non-null-optimized; \
974        it is your responsibility to ensure that the attribute is only used on types that are optimized",
975    ),
976
977    // ==========================================================================
978    // Internal attributes, Misc:
979    // ==========================================================================
980    gated!(
981        lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, EncodeCrossCrate::No, lang_items,
982        "lang items are subject to change",
983    ),
984    rustc_attr!(
985        rustc_as_ptr, Normal, template!(Word), ErrorFollowing,
986        EncodeCrossCrate::Yes,
987        "`#[rustc_as_ptr]` is used to mark functions returning pointers to their inner allocations."
988    ),
989    rustc_attr!(
990        rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,
991        EncodeCrossCrate::Yes,
992        "`#[rustc_pass_by_value]` is used to mark types that must be passed by value instead of reference."
993    ),
994    rustc_attr!(
995        rustc_never_returns_null_ptr, Normal, template!(Word), ErrorFollowing,
996        EncodeCrossCrate::Yes,
997        "`#[rustc_never_returns_null_ptr]` is used to mark functions returning non-null pointers."
998    ),
999    rustc_attr!(
1000        rustc_no_implicit_autorefs, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes,
1001        "`#[rustc_no_implicit_autorefs]` is used to mark functions for which an autoref to the dereference of a raw pointer should not be used as an argument."
1002    ),
1003    rustc_attr!(
1004        rustc_coherence_is_core, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1005        "`#![rustc_coherence_is_core]` allows inherent methods on builtin types, only intended to be used in `core`."
1006    ),
1007    rustc_attr!(
1008        rustc_coinductive, AttributeType::Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1009        "`#[rustc_coinductive]` changes a trait to be coinductive, allowing cycles in the trait solver."
1010    ),
1011    rustc_attr!(
1012        rustc_allow_incoherent_impl, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1013        "`#[rustc_allow_incoherent_impl]` has to be added to all impl items of an incoherent inherent impl."
1014    ),
1015    rustc_attr!(
1016        rustc_preserve_ub_checks, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1017        "`#![rustc_preserve_ub_checks]` prevents the designated crate from evaluating whether UB checks are enabled when optimizing MIR",
1018    ),
1019    rustc_attr!(
1020        rustc_deny_explicit_impl,
1021        AttributeType::Normal,
1022        template!(Word),
1023        ErrorFollowing,
1024        EncodeCrossCrate::No,
1025        "`#[rustc_deny_explicit_impl]` enforces that a trait can have no user-provided impls"
1026    ),
1027    rustc_attr!(
1028        rustc_do_not_implement_via_object,
1029        AttributeType::Normal,
1030        template!(Word),
1031        ErrorFollowing,
1032        EncodeCrossCrate::No,
1033        "`#[rustc_do_not_implement_via_object]` opts out of the automatic trait impl for trait objects \
1034        (`impl Trait for dyn Trait`)"
1035    ),
1036    rustc_attr!(
1037        rustc_has_incoherent_inherent_impls, AttributeType::Normal, template!(Word),
1038        ErrorFollowing, EncodeCrossCrate::Yes,
1039        "`#[rustc_has_incoherent_inherent_impls]` allows the addition of incoherent inherent impls for \
1040         the given type by annotating all impl items with `#[rustc_allow_incoherent_impl]`."
1041    ),
1042
1043    BuiltinAttribute {
1044        name: sym::rustc_diagnostic_item,
1045        // FIXME: This can be `true` once we always use `tcx.is_diagnostic_item`.
1046        encode_cross_crate: EncodeCrossCrate::Yes,
1047        type_: Normal,
1048        safety: AttributeSafety::Normal,
1049        template: template!(NameValueStr: "name"),
1050        duplicates: ErrorFollowing,
1051        gate: Gated{
1052            feature: sym::rustc_attrs,
1053            message: "use of an internal attribute",
1054            check: Features::rustc_attrs,
1055            notes: &["the `#[rustc_diagnostic_item]` attribute allows the compiler to reference types \
1056            from the standard library for diagnostic purposes"],
1057        },
1058    },
1059    gated!(
1060        // Used in resolve:
1061        prelude_import, Normal, template!(Word), WarnFollowing,
1062        EncodeCrossCrate::No, "`#[prelude_import]` is for use by rustc only",
1063    ),
1064    gated!(
1065        rustc_paren_sugar, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1066        unboxed_closures, "unboxed_closures are still evolving",
1067    ),
1068    rustc_attr!(
1069        rustc_inherit_overflow_checks, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1070        "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
1071        overflow checking behavior of several functions in the standard library that are inlined \
1072        across crates",
1073    ),
1074    rustc_attr!(
1075        rustc_reservation_impl, Normal,
1076        template!(NameValueStr: "reservation message"), ErrorFollowing, EncodeCrossCrate::Yes,
1077        "the `#[rustc_reservation_impl]` attribute is internally used \
1078        for reserving `impl<T> From<!> for T` as part of the effort to stabilize `!`"
1079    ),
1080    rustc_attr!(
1081        rustc_test_marker, Normal, template!(NameValueStr: "name"), WarnFollowing,
1082        EncodeCrossCrate::No, "the `#[rustc_test_marker]` attribute is used internally to track tests",
1083    ),
1084    rustc_attr!(
1085        rustc_unsafe_specialization_marker, Normal, template!(Word),
1086        WarnFollowing, EncodeCrossCrate::No,
1087        "the `#[rustc_unsafe_specialization_marker]` attribute is used to check specializations"
1088    ),
1089    rustc_attr!(
1090        rustc_specialization_trait, Normal, template!(Word),
1091        WarnFollowing, EncodeCrossCrate::No,
1092        "the `#[rustc_specialization_trait]` attribute is used to check specializations"
1093    ),
1094    rustc_attr!(
1095        rustc_main, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1096        "the `#[rustc_main]` attribute is used internally to specify test entry point function",
1097    ),
1098    rustc_attr!(
1099        rustc_skip_during_method_dispatch, Normal, template!(List: "array, boxed_slice"), ErrorFollowing,
1100        EncodeCrossCrate::No,
1101        "the `#[rustc_skip_during_method_dispatch]` attribute is used to exclude a trait \
1102        from method dispatch when the receiver is of the following type, for compatibility in \
1103        editions < 2021 (array) or editions < 2024 (boxed_slice)."
1104    ),
1105    rustc_attr!(
1106        rustc_must_implement_one_of, Normal, template!(List: "function1, function2, ..."),
1107        ErrorFollowing, EncodeCrossCrate::No,
1108        "the `#[rustc_must_implement_one_of]` attribute is used to change minimal complete \
1109        definition of a trait. Its syntax and semantics are highly experimental and will be \
1110        subject to change before stabilization",
1111    ),
1112    rustc_attr!(
1113        rustc_doc_primitive, Normal, template!(NameValueStr: "primitive name"), ErrorFollowing,
1114        EncodeCrossCrate::Yes, "the `#[rustc_doc_primitive]` attribute is used by the standard library \
1115        to provide a way to generate documentation for primitive types",
1116    ),
1117    gated!(
1118        rustc_intrinsic, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes, intrinsics,
1119        "the `#[rustc_intrinsic]` attribute is used to declare intrinsics as function items",
1120    ),
1121    rustc_attr!(
1122        rustc_no_mir_inline, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes,
1123        "`#[rustc_no_mir_inline]` prevents the MIR inliner from inlining a function while not affecting codegen"
1124    ),
1125    rustc_attr!(
1126        rustc_force_inline, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing, EncodeCrossCrate::Yes,
1127        "`#[rustc_force_inline]` forces a free function to be inlined"
1128    ),
1129
1130    // ==========================================================================
1131    // Internal attributes, Testing:
1132    // ==========================================================================
1133
1134    rustc_attr!(TEST, rustc_effective_visibility, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
1135    rustc_attr!(
1136        TEST, rustc_outlives, Normal, template!(Word),
1137        WarnFollowing, EncodeCrossCrate::No
1138    ),
1139    rustc_attr!(
1140        TEST, rustc_capture_analysis, Normal, template!(Word),
1141        WarnFollowing, EncodeCrossCrate::No
1142    ),
1143    rustc_attr!(
1144        TEST, rustc_insignificant_dtor, Normal, template!(Word),
1145        WarnFollowing, EncodeCrossCrate::Yes
1146    ),
1147    rustc_attr!(
1148        TEST, rustc_no_implicit_bounds, CrateLevel, template!(Word),
1149        WarnFollowing, EncodeCrossCrate::No
1150    ),
1151    rustc_attr!(
1152        TEST, rustc_strict_coherence, Normal, template!(Word),
1153        WarnFollowing, EncodeCrossCrate::Yes
1154    ),
1155    rustc_attr!(
1156        TEST, rustc_variance, Normal, template!(Word),
1157        WarnFollowing, EncodeCrossCrate::No
1158    ),
1159    rustc_attr!(
1160        TEST, rustc_variance_of_opaques, Normal, template!(Word),
1161        WarnFollowing, EncodeCrossCrate::No
1162    ),
1163    rustc_attr!(
1164        TEST, rustc_hidden_type_of_opaques, Normal, template!(Word),
1165        WarnFollowing, EncodeCrossCrate::No
1166    ),
1167    rustc_attr!(
1168        TEST, rustc_layout, Normal, template!(List: "field1, field2, ..."),
1169        WarnFollowing, EncodeCrossCrate::Yes
1170    ),
1171    rustc_attr!(
1172        TEST, rustc_abi, Normal, template!(List: "field1, field2, ..."),
1173        WarnFollowing, EncodeCrossCrate::No
1174    ),
1175    rustc_attr!(
1176        TEST, rustc_regions, Normal, template!(Word),
1177        WarnFollowing, EncodeCrossCrate::No
1178    ),
1179    rustc_attr!(
1180        TEST, rustc_delayed_bug_from_inside_query, Normal,
1181        template!(Word),
1182        WarnFollowing, EncodeCrossCrate::No
1183    ),
1184    rustc_attr!(
1185        TEST, rustc_dump_user_args, Normal, template!(Word),
1186        WarnFollowing, EncodeCrossCrate::No
1187    ),
1188    rustc_attr!(
1189        TEST, rustc_evaluate_where_clauses, Normal, template!(Word), WarnFollowing,
1190        EncodeCrossCrate::Yes
1191    ),
1192    rustc_attr!(
1193        TEST, rustc_if_this_changed, Normal, template!(Word, List: "DepNode"), DuplicatesOk,
1194        EncodeCrossCrate::No
1195    ),
1196    rustc_attr!(
1197        TEST, rustc_then_this_would_need, Normal, template!(List: "DepNode"), DuplicatesOk,
1198        EncodeCrossCrate::No
1199    ),
1200    rustc_attr!(
1201        TEST, rustc_clean, Normal,
1202        template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
1203        DuplicatesOk, EncodeCrossCrate::No
1204    ),
1205    rustc_attr!(
1206        TEST, rustc_partition_reused, Normal,
1207        template!(List: r#"cfg = "...", module = "...""#), DuplicatesOk, EncodeCrossCrate::No
1208    ),
1209    rustc_attr!(
1210        TEST, rustc_partition_codegened, Normal,
1211        template!(List: r#"cfg = "...", module = "...""#), DuplicatesOk, EncodeCrossCrate::No
1212    ),
1213    rustc_attr!(
1214        TEST, rustc_expected_cgu_reuse, Normal,
1215        template!(List: r#"cfg = "...", module = "...", kind = "...""#), DuplicatesOk,
1216        EncodeCrossCrate::No
1217    ),
1218    rustc_attr!(
1219        TEST, rustc_symbol_name, Normal, template!(Word),
1220        WarnFollowing, EncodeCrossCrate::No
1221    ),
1222    rustc_attr!(
1223        TEST, rustc_def_path, Normal, template!(Word),
1224        WarnFollowing, EncodeCrossCrate::No
1225    ),
1226    rustc_attr!(
1227        TEST, rustc_mir, Normal, template!(List: "arg1, arg2, ..."),
1228        DuplicatesOk, EncodeCrossCrate::Yes
1229    ),
1230    gated!(
1231        custom_mir, Normal, template!(List: r#"dialect = "...", phase = "...""#),
1232        ErrorFollowing, EncodeCrossCrate::No,
1233        "the `#[custom_mir]` attribute is just used for the Rust test suite",
1234    ),
1235    rustc_attr!(
1236        TEST, rustc_dump_item_bounds, Normal, template!(Word),
1237        WarnFollowing, EncodeCrossCrate::No
1238    ),
1239    rustc_attr!(
1240        TEST, rustc_dump_predicates, Normal, template!(Word),
1241        WarnFollowing, EncodeCrossCrate::No
1242    ),
1243    rustc_attr!(
1244        TEST, rustc_dump_def_parents, Normal, template!(Word),
1245        WarnFollowing, EncodeCrossCrate::No
1246    ),
1247    rustc_attr!(
1248        TEST, rustc_object_lifetime_default, Normal, template!(Word),
1249        WarnFollowing, EncodeCrossCrate::No
1250    ),
1251    rustc_attr!(
1252        TEST, rustc_dump_vtable, Normal, template!(Word),
1253        WarnFollowing, EncodeCrossCrate::No
1254    ),
1255    rustc_attr!(
1256        TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/),
1257        DuplicatesOk, EncodeCrossCrate::No
1258    ),
1259    gated!(
1260        omit_gdb_pretty_printer_section, Normal, template!(Word),
1261        WarnFollowing, EncodeCrossCrate::No,
1262        "the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
1263    ),
1264    rustc_attr!(
1265        TEST, pattern_complexity_limit, CrateLevel, template!(NameValueStr: "N"),
1266        ErrorFollowing, EncodeCrossCrate::No,
1267    ),
1268];
1269
1270pub fn is_builtin_attr_name(name: Symbol) -> bool {
1271    BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
1272}
1273
1274/// Whether this builtin attribute is encoded cross crate.
1275/// This means it can be used cross crate.
1276pub fn encode_cross_crate(name: Symbol) -> bool {
1277    if let Some(attr) = BUILTIN_ATTRIBUTE_MAP.get(&name) {
1278        attr.encode_cross_crate == EncodeCrossCrate::Yes
1279    } else {
1280        true
1281    }
1282}
1283
1284pub fn is_valid_for_get_attr(name: Symbol) -> bool {
1285    BUILTIN_ATTRIBUTE_MAP.get(&name).is_some_and(|attr| match attr.duplicates {
1286        WarnFollowing | ErrorFollowing | ErrorPreceding | FutureWarnFollowing
1287        | FutureWarnPreceding => true,
1288        DuplicatesOk | WarnFollowingWordOnly => false,
1289    })
1290}
1291
1292pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>> =
1293    LazyLock::new(|| {
1294        let mut map = FxHashMap::default();
1295        for attr in BUILTIN_ATTRIBUTES.iter() {
1296            if map.insert(attr.name, attr).is_some() {
1297                panic!("duplicate builtin attribute `{}`", attr.name);
1298            }
1299        }
1300        map
1301    });
1302
1303pub fn is_stable_diagnostic_attribute(sym: Symbol, _features: &Features) -> bool {
1304    match sym {
1305        sym::on_unimplemented | sym::do_not_recommend => true,
1306        _ => false,
1307    }
1308}
rustc_feature/builtin_attrs.rs

rustc_feature/
builtin_attrs.rs
