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_data_structures::fx::FxHashMap;
9use rustc_hir::AttrStyle;
10use rustc_hir::attrs::EncodeCrossCrate;
11use rustc_span::edition::Edition;
12use rustc_span::{Symbol, sym};
13
14use crate::Features;
15
16type GateFn = fn(&Features) -> bool;
17
18pub type GatedCfg = (Symbol, Symbol, GateFn);
19
20/// `cfg(...)`'s that are feature gated.
21const GATED_CFGS: &[GatedCfg] = &[
22    // (name in cfg, feature, function to check if the feature is enabled)
23    (sym::overflow_checks, sym::cfg_overflow_checks, Features::cfg_overflow_checks),
24    (sym::ub_checks, sym::cfg_ub_checks, Features::cfg_ub_checks),
25    (sym::contract_checks, sym::cfg_contract_checks, Features::cfg_contract_checks),
26    (sym::target_thread_local, sym::cfg_target_thread_local, Features::cfg_target_thread_local),
27    (
28        sym::target_has_atomic_equal_alignment,
29        sym::cfg_target_has_atomic_equal_alignment,
30        Features::cfg_target_has_atomic_equal_alignment,
31    ),
32    (
33        sym::target_has_atomic_load_store,
34        sym::cfg_target_has_atomic,
35        Features::cfg_target_has_atomic,
36    ),
37    (sym::sanitize, sym::cfg_sanitize, Features::cfg_sanitize),
38    (sym::version, sym::cfg_version, Features::cfg_version),
39    (sym::relocation_model, sym::cfg_relocation_model, Features::cfg_relocation_model),
40    (sym::sanitizer_cfi_generalize_pointers, sym::cfg_sanitizer_cfi, Features::cfg_sanitizer_cfi),
41    (sym::sanitizer_cfi_normalize_integers, sym::cfg_sanitizer_cfi, Features::cfg_sanitizer_cfi),
42    // this is consistent with naming of the compiler flag it's for
43    (sym::fmt_debug, sym::fmt_debug, Features::fmt_debug),
44    (sym::emscripten_wasm_eh, sym::cfg_emscripten_wasm_eh, Features::cfg_emscripten_wasm_eh),
45    (
46        sym::target_has_reliable_f16,
47        sym::cfg_target_has_reliable_f16_f128,
48        Features::cfg_target_has_reliable_f16_f128,
49    ),
50    (
51        sym::target_has_reliable_f16_math,
52        sym::cfg_target_has_reliable_f16_f128,
53        Features::cfg_target_has_reliable_f16_f128,
54    ),
55    (
56        sym::target_has_reliable_f128,
57        sym::cfg_target_has_reliable_f16_f128,
58        Features::cfg_target_has_reliable_f16_f128,
59    ),
60    (
61        sym::target_has_reliable_f128_math,
62        sym::cfg_target_has_reliable_f16_f128,
63        Features::cfg_target_has_reliable_f16_f128,
64    ),
65];
66
67/// Find a gated cfg determined by the `pred`icate which is given the cfg's name.
68pub fn find_gated_cfg(pred: impl Fn(Symbol) -> bool) -> Option<&'static GatedCfg> {
69    GATED_CFGS.iter().find(|(cfg_sym, ..)| pred(*cfg_sym))
70}
71
72// If you change this, please modify `src/doc/unstable-book` as well. You must
73// move that documentation into the relevant place in the other docs, and
74// remove the chapter on the flag.
75
76#[derive(Copy, Clone, PartialEq, Debug)]
77pub enum AttributeType {
78    /// Normal, builtin attribute that is consumed
79    /// by the compiler before the unused_attribute check
80    Normal,
81
82    /// Builtin attribute that is only allowed at the crate level
83    CrateLevel,
84}
85
86#[derive(Copy, Clone, PartialEq, Debug)]
87pub enum AttributeSafety {
88    /// Normal attribute that does not need `#[unsafe(...)]`
89    Normal,
90
91    /// Unsafe attribute that requires safety obligations to be discharged.
92    ///
93    /// An error is emitted when `#[unsafe(...)]` is omitted, except when the attribute's edition
94    /// is less than the one stored in `unsafe_since`. This handles attributes that were safe in
95    /// earlier editions, but become unsafe in later ones.
96    Unsafe { unsafe_since: Option<Edition> },
97}
98
99#[derive(Clone, Debug, Copy)]
100pub enum AttributeGate {
101    /// A gated attribute which requires a feature gate to be enabled.
102    Gated {
103        /// The feature gate, for example `#![feature(rustc_attrs)]` for rustc_* attributes.
104        feature: Symbol,
105        /// The error message displayed when an attempt is made to use the attribute without its feature gate.
106        message: &'static str,
107        /// Check function to be called during the `PostExpansionVisitor` pass.
108        check: fn(&Features) -> bool,
109        /// Notes to be displayed when an attempt is made to use the attribute without its feature gate.
110        notes: &'static [&'static str],
111    },
112    /// Ungated attribute, can be used on all release channels
113    Ungated,
114}
115
116// FIXME(jdonszelmann): move to rustc_hir::attrs
117/// A template that the attribute input must match.
118/// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
119#[derive(Clone, Copy, Default)]
120pub struct AttributeTemplate {
121    /// If `true`, the attribute is allowed to be a bare word like `#[test]`.
122    pub word: bool,
123    /// If `Some`, the attribute is allowed to take a list of items like `#[allow(..)]`.
124    pub list: Option<&'static [&'static str]>,
125    /// If non-empty, the attribute is allowed to take a list containing exactly
126    /// one of the listed words, like `#[coverage(off)]`.
127    pub one_of: &'static [Symbol],
128    /// If `Some`, the attribute is allowed to be a name/value pair where the
129    /// value is a string, like `#[must_use = "reason"]`.
130    pub name_value_str: Option<&'static [&'static str]>,
131    /// A link to the document for this attribute.
132    pub docs: Option<&'static str>,
133}
134
135impl AttributeTemplate {
136    pub fn suggestions(&self, style: AttrStyle, name: impl std::fmt::Display) -> Vec<String> {
137        let mut suggestions = vec![];
138        let inner = match style {
139            AttrStyle::Outer => "",
140            AttrStyle::Inner => "!",
141        };
142        if self.word {
143            suggestions.push(format!("#{inner}[{name}]"));
144        }
145        if let Some(descr) = self.list {
146            for descr in descr {
147                suggestions.push(format!("#{inner}[{name}({descr})]"));
148            }
149        }
150        suggestions.extend(self.one_of.iter().map(|&word| format!("#{inner}[{name}({word})]")));
151        if let Some(descr) = self.name_value_str {
152            for descr in descr {
153                suggestions.push(format!("#{inner}[{name} = \"{descr}\"]"));
154            }
155        }
156        suggestions.sort();
157
158        suggestions
159    }
160}
161
162/// How to handle multiple duplicate attributes on the same item.
163#[derive(Clone, Copy, Default)]
164pub enum AttributeDuplicates {
165    /// Duplicates of this attribute are allowed.
166    ///
167    /// This should only be used with attributes where duplicates have semantic
168    /// meaning, or some kind of "additive" behavior. For example, `#[warn(..)]`
169    /// can be specified multiple times, and it combines all the entries. Or use
170    /// this if there is validation done elsewhere.
171    #[default]
172    DuplicatesOk,
173    /// Duplicates after the first attribute will be an unused_attribute warning.
174    ///
175    /// This is usually used for "word" attributes, where they are used as a
176    /// boolean marker, like `#[used]`. It is not necessarily wrong that there
177    /// are duplicates, but the others should probably be removed.
178    WarnFollowing,
179    /// Same as `WarnFollowing`, but only issues warnings for word-style attributes.
180    ///
181    /// This is only for special cases, for example multiple `#[macro_use]` can
182    /// be warned, but multiple `#[macro_use(...)]` should not because the list
183    /// form has different meaning from the word form.
184    WarnFollowingWordOnly,
185    /// Duplicates after the first attribute will be an error.
186    ///
187    /// This should be used where duplicates would be ignored, but carry extra
188    /// meaning that could cause confusion. For example, `#[stable(since="1.0")]
189    /// #[stable(since="2.0")]`, which version should be used for `stable`?
190    ErrorFollowing,
191    /// Duplicates preceding the last instance of the attribute will be an error.
192    ///
193    /// This is the same as `ErrorFollowing`, except the last attribute is the
194    /// one that is "used". This is typically used in cases like codegen
195    /// attributes which usually only honor the last attribute.
196    ErrorPreceding,
197    /// Duplicates after the first attribute will be an unused_attribute warning
198    /// with a note that this will be an error in the future.
199    ///
200    /// This should be used for attributes that should be `ErrorFollowing`, but
201    /// because older versions of rustc silently accepted (and ignored) the
202    /// attributes, this is used to transition.
203    FutureWarnFollowing,
204    /// Duplicates preceding the last instance of the attribute will be a
205    /// warning, with a note that this will be an error in the future.
206    ///
207    /// This is the same as `FutureWarnFollowing`, except the last attribute is
208    /// the one that is "used". Ideally these can eventually migrate to
209    /// `ErrorPreceding`.
210    FutureWarnPreceding,
211}
212
213/// A convenience macro for constructing attribute templates.
214/// E.g., `template!(Word, List: "description")` means that the attribute
215/// supports forms `#[attr]` and `#[attr(description)]`.
216#[macro_export]
217macro_rules! template {
218    (Word) => { $crate::template!(@ true, None, &[], None, None) };
219    (Word, $link: literal) => { $crate::template!(@ true, None, &[], None, Some($link)) };
220    (List: $descr: expr) => { $crate::template!(@ false, Some($descr), &[], None, None) };
221    (List: $descr: expr, $link: literal) => { $crate::template!(@ false, Some($descr), &[], None, Some($link)) };
222    (OneOf: $one_of: expr) => { $crate::template!(@ false, None, $one_of, None, None) };
223    (NameValueStr: [$($descr: literal),* $(,)?]) => { $crate::template!(@ false, None, &[], Some(&[$($descr,)*]), None) };
224    (NameValueStr: [$($descr: literal),* $(,)?], $link: literal) => { $crate::template!(@ false, None, &[], Some(&[$($descr,)*]), Some($link)) };
225    (NameValueStr: $descr: literal) => { $crate::template!(@ false, None, &[], Some(&[$descr]), None) };
226    (NameValueStr: $descr: literal, $link: literal) => { $crate::template!(@ false, None, &[], Some(&[$descr]), Some($link)) };
227    (Word, List: $descr: expr) => { $crate::template!(@ true, Some($descr), &[], None, None) };
228    (Word, List: $descr: expr, $link: literal) => { $crate::template!(@ true, Some($descr), &[], None, Some($link)) };
229    (Word, NameValueStr: $descr: expr) => { $crate::template!(@ true, None, &[], Some(&[$descr]), None) };
230    (Word, NameValueStr: $descr: expr, $link: literal) => { $crate::template!(@ true, None, &[], Some(&[$descr]), Some($link)) };
231    (List: $descr1: expr, NameValueStr: $descr2: expr) => {
232        $crate::template!(@ false, Some($descr1), &[], Some(&[$descr2]), None)
233    };
234    (List: $descr1: expr, NameValueStr: $descr2: expr, $link: literal) => {
235        $crate::template!(@ false, Some($descr1), &[], Some(&[$descr2]), Some($link))
236    };
237    (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
238        $crate::template!(@ true, Some($descr1), &[], Some(&[$descr2]), None)
239    };
240    (Word, List: $descr1: expr, NameValueStr: $descr2: expr, $link: literal) => {
241        $crate::template!(@ true, Some($descr1), &[], Some(&[$descr2]), Some($link))
242    };
243    (@ $word: expr, $list: expr, $one_of: expr, $name_value_str: expr, $link: expr) => { $crate::AttributeTemplate {
244        word: $word, list: $list, one_of: $one_of, name_value_str: $name_value_str, docs: $link,
245    } };
246}
247
248macro_rules! ungated {
249    (unsafe($edition:ident) $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr $(,)?) => {
250        BuiltinAttribute {
251            name: sym::$attr,
252            encode_cross_crate: $encode_cross_crate,
253            type_: $typ,
254            safety: AttributeSafety::Unsafe { unsafe_since: Some(Edition::$edition) },
255            template: $tpl,
256            gate: Ungated,
257            duplicates: $duplicates,
258        }
259    };
260    (unsafe $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr $(,)?) => {
261        BuiltinAttribute {
262            name: sym::$attr,
263            encode_cross_crate: $encode_cross_crate,
264            type_: $typ,
265            safety: AttributeSafety::Unsafe { unsafe_since: None },
266            template: $tpl,
267            gate: Ungated,
268            duplicates: $duplicates,
269        }
270    };
271    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr $(,)?) => {
272        BuiltinAttribute {
273            name: sym::$attr,
274            encode_cross_crate: $encode_cross_crate,
275            type_: $typ,
276            safety: AttributeSafety::Normal,
277            template: $tpl,
278            gate: Ungated,
279            duplicates: $duplicates,
280        }
281    };
282}
283
284macro_rules! gated {
285    (unsafe $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $gate:ident, $message:expr $(,)?) => {
286        BuiltinAttribute {
287            name: sym::$attr,
288            encode_cross_crate: $encode_cross_crate,
289            type_: $typ,
290            safety: AttributeSafety::Unsafe { unsafe_since: None },
291            template: $tpl,
292            duplicates: $duplicates,
293            gate: Gated {
294                feature: sym::$gate,
295                message: $message,
296                check: Features::$gate,
297                notes: &[],
298            },
299        }
300    };
301    (unsafe $attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $message:expr $(,)?) => {
302        BuiltinAttribute {
303            name: sym::$attr,
304            encode_cross_crate: $encode_cross_crate,
305            type_: $typ,
306            safety: AttributeSafety::Unsafe { unsafe_since: None },
307            template: $tpl,
308            duplicates: $duplicates,
309            gate: Gated {
310                feature: sym::$attr,
311                message: $message,
312                check: Features::$attr,
313                notes: &[],
314            },
315        }
316    };
317    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $gate:ident, $message:expr $(,)?) => {
318        BuiltinAttribute {
319            name: sym::$attr,
320            encode_cross_crate: $encode_cross_crate,
321            type_: $typ,
322            safety: AttributeSafety::Normal,
323            template: $tpl,
324            duplicates: $duplicates,
325            gate: Gated {
326                feature: sym::$gate,
327                message: $message,
328                check: Features::$gate,
329                notes: &[],
330            },
331        }
332    };
333    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $message:expr $(,)?) => {
334        BuiltinAttribute {
335            name: sym::$attr,
336            encode_cross_crate: $encode_cross_crate,
337            type_: $typ,
338            safety: AttributeSafety::Normal,
339            template: $tpl,
340            duplicates: $duplicates,
341            gate: Gated {
342                feature: sym::$attr,
343                message: $message,
344                check: Features::$attr,
345                notes: &[],
346            },
347        }
348    };
349}
350
351macro_rules! rustc_attr {
352    (TEST, $attr:ident, $typ:expr, $tpl:expr, $duplicate:expr, $encode_cross_crate:expr $(,)?) => {
353        rustc_attr!(
354            $attr,
355            $typ,
356            $tpl,
357            $duplicate,
358            $encode_cross_crate,
359            concat!(
360                "the `#[",
361                stringify!($attr),
362                "]` attribute is used for rustc unit tests"
363            ),
364        )
365    };
366    ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr, $encode_cross_crate:expr, $($notes:expr),* $(,)?) => {
367        BuiltinAttribute {
368            name: sym::$attr,
369            encode_cross_crate: $encode_cross_crate,
370            type_: $typ,
371            safety: AttributeSafety::Normal,
372            template: $tpl,
373            duplicates: $duplicates,
374            gate: Gated {
375                feature: sym::rustc_attrs,
376                message: "use of an internal attribute",
377                check: Features::rustc_attrs,
378                notes: &[
379                    concat!("the `#[",
380                    stringify!($attr),
381                    "]` attribute is an internal implementation detail that will never be stable"),
382                    $($notes),*
383                    ]
384            },
385        }
386    };
387}
388
389macro_rules! experimental {
390    ($attr:ident) => {
391        concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
392    };
393}
394
395pub struct BuiltinAttribute {
396    pub name: Symbol,
397    /// Whether this attribute is encode cross crate.
398    ///
399    /// If so, it is encoded in the crate metadata.
400    /// Otherwise, it can only be used in the local crate.
401    pub encode_cross_crate: EncodeCrossCrate,
402    pub type_: AttributeType,
403    pub safety: AttributeSafety,
404    pub template: AttributeTemplate,
405    pub duplicates: AttributeDuplicates,
406    pub gate: AttributeGate,
407}
408
409/// Attributes that have a special meaning to rustc or rustdoc.
410#[rustfmt::skip]
411pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
412    // ==========================================================================
413    // Stable attributes:
414    // ==========================================================================
415
416    // Conditional compilation:
417    ungated!(
418        cfg, Normal,
419        template!(
420            List: &["predicate"],
421            "https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute"
422        ),
423        DuplicatesOk, EncodeCrossCrate::Yes
424    ),
425    ungated!(
426        cfg_attr, Normal,
427        template!(
428            List: &["predicate, attr1, attr2, ..."],
429            "https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute"
430        ),
431        DuplicatesOk, EncodeCrossCrate::Yes
432    ),
433
434    // Testing:
435    ungated!(
436        ignore, Normal,
437        template!(
438            Word,
439            NameValueStr: "reason",
440            "https://doc.rust-lang.org/reference/attributes/testing.html#the-ignore-attribute"
441        ),
442        WarnFollowing, EncodeCrossCrate::No,
443    ),
444    ungated!(
445        should_panic, Normal,
446        template!(
447            Word,
448            List: &[r#"expected = "reason""#],
449            NameValueStr: "reason",
450            "https://doc.rust-lang.org/reference/attributes/testing.html#the-should_panic-attribute"
451        ),
452        FutureWarnFollowing, EncodeCrossCrate::No,
453    ),
454    // FIXME(Centril): This can be used on stable but shouldn't.
455    ungated!(
456        reexport_test_harness_main, CrateLevel, template!(NameValueStr: "name"), ErrorFollowing,
457        EncodeCrossCrate::No,
458    ),
459
460    // Macros:
461    ungated!(
462        automatically_derived, Normal,
463        template!(
464            Word,
465            "https://doc.rust-lang.org/reference/attributes/derive.html#the-automatically_derived-attribute"
466        ),
467        WarnFollowing, EncodeCrossCrate::Yes
468    ),
469    ungated!(
470        macro_use, Normal,
471        template!(
472            Word,
473            List: &["name1, name2, ..."],
474            "https://doc.rust-lang.org/reference/macros-by-example.html#the-macro_use-attribute"
475        ),
476        WarnFollowingWordOnly, EncodeCrossCrate::No,
477    ),
478    ungated!(macro_escape, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No), // Deprecated synonym for `macro_use`.
479    ungated!(
480        macro_export, Normal,
481        template!(
482            Word,
483            List: &["local_inner_macros"],
484            "https://doc.rust-lang.org/reference/macros-by-example.html#path-based-scope"
485        ),
486        WarnFollowing, EncodeCrossCrate::Yes
487    ),
488    ungated!(
489        proc_macro, Normal,
490        template!(
491            Word,
492            "https://doc.rust-lang.org/reference/procedural-macros.html#function-like-procedural-macros"),
493        ErrorFollowing, EncodeCrossCrate::No
494    ),
495    ungated!(
496        proc_macro_derive, Normal,
497        template!(
498            List: &["TraitName", "TraitName, attributes(name1, name2, ...)"],
499            "https://doc.rust-lang.org/reference/procedural-macros.html#derive-macros"
500        ),
501        ErrorFollowing, EncodeCrossCrate::No,
502    ),
503    ungated!(
504        proc_macro_attribute, Normal,
505        template!(Word, "https://doc.rust-lang.org/reference/procedural-macros.html#attribute-macros"),
506        ErrorFollowing, EncodeCrossCrate::No
507    ),
508
509    // Lints:
510    ungated!(
511        warn, Normal,
512        template!(
513            List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
514            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
515        ),
516        DuplicatesOk, EncodeCrossCrate::No,
517    ),
518    ungated!(
519        allow, Normal,
520        template!(
521            List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
522            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
523        ),
524        DuplicatesOk, EncodeCrossCrate::No,
525    ),
526    ungated!(
527        expect, Normal,
528        template!(
529            List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
530            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
531        ),
532        DuplicatesOk, EncodeCrossCrate::No,
533    ),
534    ungated!(
535        forbid, Normal,
536        template!(
537            List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
538            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
539        ),
540        DuplicatesOk, EncodeCrossCrate::No
541    ),
542    ungated!(
543        deny, Normal,
544        template!(
545            List: &["lint1", "lint1, lint2, ...", r#"lint1, lint2, lint3, reason = "...""#],
546            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#lint-check-attributes"
547        ),
548        DuplicatesOk, EncodeCrossCrate::No
549    ),
550    ungated!(
551        must_use, Normal,
552        template!(
553            Word,
554            NameValueStr: "reason",
555            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-must_use-attribute"
556        ),
557        FutureWarnFollowing, EncodeCrossCrate::Yes
558    ),
559    gated!(
560        must_not_suspend, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing,
561        EncodeCrossCrate::Yes, experimental!(must_not_suspend)
562    ),
563    ungated!(
564        deprecated, Normal,
565        template!(
566            Word,
567            List: &[r#"/*opt*/ since = "version", /*opt*/ note = "reason""#],
568            NameValueStr: "reason",
569            "https://doc.rust-lang.org/reference/attributes/diagnostics.html#the-deprecated-attribute"
570        ),
571        ErrorFollowing, EncodeCrossCrate::Yes
572    ),
573
574    // Crate properties:
575    ungated!(
576        crate_name, CrateLevel,
577        template!(
578            NameValueStr: "name",
579            "https://doc.rust-lang.org/reference/crates-and-source-files.html#the-crate_name-attribute"
580        ),
581        FutureWarnFollowing, EncodeCrossCrate::No,
582    ),
583    ungated!(
584        crate_type, CrateLevel,
585        template!(
586            NameValueStr: ["bin", "lib", "dylib", "cdylib", "rlib", "staticlib", "sdylib", "proc-macro"],
587            "https://doc.rust-lang.org/reference/linkage.html"
588        ),
589        DuplicatesOk, EncodeCrossCrate::No,
590    ),
591
592    // ABI, linking, symbols, and FFI
593    ungated!(
594        link, Normal,
595        template!(List: &[
596            r#"name = "...""#,
597            r#"name = "...", kind = "dylib|static|...""#,
598            r#"name = "...", wasm_import_module = "...""#,
599            r#"name = "...", import_name_type = "decorated|noprefix|undecorated""#,
600            r#"name = "...", kind = "dylib|static|...", wasm_import_module = "...", import_name_type = "decorated|noprefix|undecorated""#,
601        ], "https://doc.rust-lang.org/reference/items/external-blocks.html#the-link-attribute"),
602        DuplicatesOk, EncodeCrossCrate::No,
603    ),
604    ungated!(
605        link_name, Normal,
606        template!(NameValueStr: "name", "https://doc.rust-lang.org/reference/items/external-blocks.html#the-link_name-attribute"),
607        FutureWarnPreceding, EncodeCrossCrate::Yes
608    ),
609    ungated!(
610        no_link, Normal,
611        template!(Word, "https://doc.rust-lang.org/reference/items/extern-crates.html#the-no_link-attribute"),
612        WarnFollowing, EncodeCrossCrate::No
613    ),
614    ungated!(
615        repr, Normal,
616        template!(
617            List: &["C", "Rust", "transparent", "align(...)", "packed(...)", "<integer type>"],
618            "https://doc.rust-lang.org/reference/type-layout.html#representations"
619        ),
620        DuplicatesOk, EncodeCrossCrate::No
621    ),
622    // FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
623    gated!(rustc_align, Normal, template!(List: &["alignment"]), DuplicatesOk, EncodeCrossCrate::No, fn_align, experimental!(rustc_align)),
624    gated!(rustc_align_static, Normal, template!(List: &["alignment"]), DuplicatesOk, EncodeCrossCrate::No, static_align, experimental!(rustc_align_static)),
625    ungated!(
626        unsafe(Edition2024) export_name, Normal,
627        template!(NameValueStr: "name", "https://doc.rust-lang.org/reference/abi.html#the-export_name-attribute"),
628        FutureWarnPreceding, EncodeCrossCrate::No
629    ),
630    ungated!(
631        unsafe(Edition2024) link_section, Normal,
632        template!(NameValueStr: "name", "https://doc.rust-lang.org/reference/abi.html#the-link_section-attribute"),
633        FutureWarnPreceding, EncodeCrossCrate::No
634    ),
635    ungated!(
636        unsafe(Edition2024) no_mangle, Normal,
637        template!(Word, "https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute"),
638        WarnFollowing, EncodeCrossCrate::No
639    ),
640    ungated!(
641        used, Normal,
642        template!(Word, List: &["compiler", "linker"], "https://doc.rust-lang.org/reference/abi.html#the-used-attribute"),
643        WarnFollowing, EncodeCrossCrate::No
644    ),
645    ungated!(
646        link_ordinal, Normal,
647        template!(List: &["ordinal"], "https://doc.rust-lang.org/reference/items/external-blocks.html#the-link_ordinal-attribute"),
648        ErrorPreceding, EncodeCrossCrate::Yes
649    ),
650    ungated!(
651        unsafe naked, Normal,
652        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-naked-attribute"),
653        WarnFollowing, EncodeCrossCrate::No
654    ),
655
656    // Limits:
657    ungated!(
658        recursion_limit, CrateLevel,
659        template!(NameValueStr: "N", "https://doc.rust-lang.org/reference/attributes/limits.html#the-recursion_limit-attribute"),
660        FutureWarnFollowing, EncodeCrossCrate::No
661    ),
662    ungated!(
663        type_length_limit, CrateLevel,
664        template!(NameValueStr: "N", "https://doc.rust-lang.org/reference/attributes/limits.html#the-type_length_limit-attribute"),
665        FutureWarnFollowing, EncodeCrossCrate::No
666    ),
667    gated!(
668        move_size_limit, CrateLevel, template!(NameValueStr: "N"), ErrorFollowing,
669        EncodeCrossCrate::No, large_assignments, experimental!(move_size_limit)
670    ),
671
672    // Entry point:
673    ungated!(
674        no_main, CrateLevel,
675        template!(Word, "https://doc.rust-lang.org/reference/crates-and-source-files.html#the-no_main-attribute"),
676        WarnFollowing, EncodeCrossCrate::No
677    ),
678
679    // Modules, prelude, and resolution:
680    ungated!(
681        path, Normal,
682        template!(NameValueStr: "file", "https://doc.rust-lang.org/reference/items/modules.html#the-path-attribute"),
683        FutureWarnFollowing, EncodeCrossCrate::No
684    ),
685    ungated!(
686        no_std, CrateLevel,
687        template!(Word, "https://doc.rust-lang.org/reference/names/preludes.html#the-no_std-attribute"),
688        WarnFollowing, EncodeCrossCrate::No
689    ),
690    ungated!(
691        no_implicit_prelude, Normal,
692        template!(Word, "https://doc.rust-lang.org/reference/names/preludes.html#the-no_implicit_prelude-attribute"),
693        WarnFollowing, EncodeCrossCrate::No
694    ),
695    ungated!(
696        non_exhaustive, Normal,
697        template!(Word, "https://doc.rust-lang.org/reference/attributes/type_system.html#the-non_exhaustive-attribute"),
698        WarnFollowing, EncodeCrossCrate::Yes
699    ),
700
701    // Runtime
702    ungated!(
703        windows_subsystem, CrateLevel,
704        template!(NameValueStr: ["windows", "console"], "https://doc.rust-lang.org/reference/runtime.html#the-windows_subsystem-attribute"),
705        FutureWarnFollowing, EncodeCrossCrate::No
706    ),
707    ungated!( // RFC 2070
708        panic_handler, Normal,
709        template!(Word, "https://doc.rust-lang.org/reference/panic.html#the-panic_handler-attribute"),
710        WarnFollowing, EncodeCrossCrate::Yes
711    ),
712
713    // Code generation:
714    ungated!(
715        inline, Normal,
716        template!(
717            Word,
718            List: &["always", "never"],
719            "https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute"
720        ),
721        FutureWarnFollowing, EncodeCrossCrate::No
722    ),
723    ungated!(
724        cold, Normal,
725        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-cold-attribute"),
726        WarnFollowing, EncodeCrossCrate::No
727    ),
728    ungated!(
729        no_builtins, CrateLevel,
730        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-no_builtins-attribute"),
731        WarnFollowing, EncodeCrossCrate::Yes
732    ),
733    ungated!(
734        target_feature, Normal,
735        template!(List: &[r#"enable = "name""#], "https://doc.rust-lang.org/reference/attributes/codegen.html#the-target_feature-attribute"),
736        DuplicatesOk, EncodeCrossCrate::No,
737    ),
738    ungated!(
739        track_caller, Normal,
740        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-track_caller-attribute"),
741        WarnFollowing, EncodeCrossCrate::Yes
742    ),
743    ungated!(
744        instruction_set, Normal,
745        template!(List: &["set"], "https://doc.rust-lang.org/reference/attributes/codegen.html#the-instruction_set-attribute"),
746        ErrorPreceding, EncodeCrossCrate::No
747    ),
748    gated!(
749        unsafe force_target_feature, Normal, template!(List: &[r#"enable = "name""#]),
750        DuplicatesOk, EncodeCrossCrate::No, effective_target_features, experimental!(force_target_feature)
751    ),
752    gated!(
753        sanitize, Normal, template!(List: &[r#"address = "on|off""#, r#"kernel_address = "on|off""#, r#"cfi = "on|off""#, r#"hwaddress = "on|off""#, r#"kcfi = "on|off""#, r#"memory = "on|off""#, r#"memtag = "on|off""#, r#"shadow_call_stack = "on|off""#, r#"thread = "on|off""#]), ErrorPreceding,
754        EncodeCrossCrate::No, sanitize, experimental!(sanitize),
755    ),
756    gated!(
757        coverage, Normal, template!(OneOf: &[sym::off, sym::on]),
758        ErrorPreceding, EncodeCrossCrate::No,
759        coverage_attribute, experimental!(coverage)
760    ),
761
762    ungated!(
763        doc, Normal,
764        template!(
765            List: &["hidden", "inline"],
766            NameValueStr: "string",
767            "https://doc.rust-lang.org/rustdoc/write-documentation/the-doc-attribute.html"
768        ),
769        DuplicatesOk, EncodeCrossCrate::Yes
770    ),
771
772    // Debugging
773    ungated!(
774        debugger_visualizer, Normal,
775        template!(
776            List: &[r#"natvis_file = "...", gdb_script_file = "...""#],
777            "https://doc.rust-lang.org/reference/attributes/debugger.html#the-debugger_visualizer-attribute"
778        ),
779        DuplicatesOk, EncodeCrossCrate::No
780    ),
781    ungated!(
782        collapse_debuginfo, Normal,
783        template!(
784            List: &["no", "external", "yes"],
785            "https://doc.rust-lang.org/reference/attributes/debugger.html#the-collapse_debuginfo-attribute"
786        ),
787        ErrorFollowing, EncodeCrossCrate::Yes
788    ),
789
790    // ==========================================================================
791    // Unstable attributes:
792    // ==========================================================================
793
794    // Linking:
795    gated!(
796        export_stable, Normal, template!(Word), WarnFollowing,
797        EncodeCrossCrate::No, experimental!(export_stable)
798    ),
799
800    // Testing:
801    gated!(
802        test_runner, CrateLevel, template!(List: &["path"]), ErrorFollowing,
803        EncodeCrossCrate::Yes, custom_test_frameworks,
804        "custom test frameworks are an unstable feature",
805    ),
806    // RFC #1268
807    gated!(
808        marker, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
809        marker_trait_attr, experimental!(marker)
810    ),
811    gated!(
812        thread_local, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
813        "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
814    ),
815    gated!(
816        no_core, CrateLevel, template!(Word), WarnFollowing,
817        EncodeCrossCrate::No, experimental!(no_core)
818    ),
819    // RFC 2412
820    gated!(
821        optimize, Normal, template!(List: &["none", "size", "speed"]), ErrorPreceding,
822        EncodeCrossCrate::No, optimize_attribute, experimental!(optimize)
823    ),
824
825    gated!(
826        unsafe ffi_pure, Normal, template!(Word), WarnFollowing,
827        EncodeCrossCrate::No, experimental!(ffi_pure)
828    ),
829    gated!(
830        unsafe ffi_const, Normal, template!(Word), WarnFollowing,
831        EncodeCrossCrate::No, experimental!(ffi_const)
832    ),
833    gated!(
834        register_tool, CrateLevel, template!(List: &["tool1, tool2, ..."]), DuplicatesOk,
835        EncodeCrossCrate::No, experimental!(register_tool),
836    ),
837
838    // RFC 2632
839    // FIXME(const_trait_impl) remove this
840    gated!(
841        const_trait, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No, const_trait_impl,
842        "`const_trait` is a temporary placeholder for marking a trait that is suitable for `const` \
843        `impls` and all default bodies as `const`, which may be removed or renamed in the \
844        future."
845    ),
846    // lang-team MCP 147
847    gated!(
848        deprecated_safe, Normal, template!(List: &[r#"since = "version", note = "...""#]), ErrorFollowing,
849        EncodeCrossCrate::Yes, experimental!(deprecated_safe),
850    ),
851
852    // `#[cfi_encoding = ""]`
853    gated!(
854        cfi_encoding, Normal, template!(NameValueStr: "encoding"), ErrorPreceding,
855        EncodeCrossCrate::Yes, experimental!(cfi_encoding)
856    ),
857
858    // `#[coroutine]` attribute to be applied to closures to make them coroutines instead
859    gated!(
860        coroutine, Normal, template!(Word), ErrorFollowing,
861        EncodeCrossCrate::No, coroutines, experimental!(coroutine)
862    ),
863
864    // RFC 3543
865    // `#[patchable_function_entry(prefix_nops = m, entry_nops = n)]`
866    gated!(
867        patchable_function_entry, Normal, template!(List: &["prefix_nops = m, entry_nops = n"]), ErrorPreceding,
868        EncodeCrossCrate::Yes, experimental!(patchable_function_entry)
869    ),
870
871    // Probably temporary component of min_generic_const_args.
872    // `#[type_const] const ASSOC: usize;`
873    gated!(
874        type_const, Normal, template!(Word), ErrorFollowing,
875        EncodeCrossCrate::Yes, min_generic_const_args, experimental!(type_const),
876    ),
877
878    // The `#[loop_match]` and `#[const_continue]` attributes are part of the
879    // lang experiment for RFC 3720 tracked in:
880    //
881    // - https://github.com/rust-lang/rust/issues/132306
882    gated!(
883        const_continue, Normal, template!(Word), ErrorFollowing,
884        EncodeCrossCrate::No, loop_match, experimental!(const_continue)
885    ),
886    gated!(
887        loop_match, Normal, template!(Word), ErrorFollowing,
888        EncodeCrossCrate::No, loop_match, experimental!(loop_match)
889    ),
890
891    // ==========================================================================
892    // Internal attributes: Stability, deprecation, and unsafe:
893    // ==========================================================================
894
895    ungated!(
896        feature, CrateLevel,
897        template!(List: &["name1, name2, ..."]), DuplicatesOk, EncodeCrossCrate::No,
898    ),
899    // DuplicatesOk since it has its own validation
900    ungated!(
901        stable, Normal,
902        template!(List: &[r#"feature = "name", since = "version""#]), DuplicatesOk, EncodeCrossCrate::No,
903    ),
904    ungated!(
905        unstable, Normal,
906        template!(List: &[r#"feature = "name", reason = "...", issue = "N""#]), DuplicatesOk,
907        EncodeCrossCrate::Yes
908    ),
909    ungated!(
910        unstable_feature_bound, Normal, template!(Word, List: &["feat1, feat2, ..."]),
911        DuplicatesOk, EncodeCrossCrate::No,
912    ),
913    ungated!(
914        rustc_const_unstable, Normal, template!(List: &[r#"feature = "name""#]),
915        DuplicatesOk, EncodeCrossCrate::Yes
916    ),
917    ungated!(
918        rustc_const_stable, Normal,
919        template!(List: &[r#"feature = "name""#]), DuplicatesOk, EncodeCrossCrate::No,
920    ),
921    ungated!(
922        rustc_default_body_unstable, Normal,
923        template!(List: &[r#"feature = "name", reason = "...", issue = "N""#]),
924        DuplicatesOk, EncodeCrossCrate::No
925    ),
926    gated!(
927        allow_internal_unstable, Normal, template!(Word, List: &["feat1, feat2, ..."]),
928        DuplicatesOk, EncodeCrossCrate::Yes,
929        "allow_internal_unstable side-steps feature gating and stability checks",
930    ),
931    gated!(
932        allow_internal_unsafe, Normal, template!(Word), WarnFollowing,
933        EncodeCrossCrate::No, "allow_internal_unsafe side-steps the unsafe_code lint",
934    ),
935    rustc_attr!(
936        rustc_allowed_through_unstable_modules, Normal, template!(NameValueStr: "deprecation message"),
937        WarnFollowing, EncodeCrossCrate::No,
938        "rustc_allowed_through_unstable_modules special cases accidental stabilizations of stable items \
939        through unstable paths"
940    ),
941    rustc_attr!(
942        rustc_deprecated_safe_2024, Normal, template!(List: &[r#"audit_that = "...""#]),
943        ErrorFollowing, EncodeCrossCrate::Yes,
944        "`#[rustc_deprecated_safe_2024]` is used to declare functions unsafe across the edition 2024 boundary",
945    ),
946    rustc_attr!(
947        rustc_pub_transparent, Normal, template!(Word),
948        ErrorFollowing, EncodeCrossCrate::Yes,
949        "used internally to mark types with a `transparent` representation when it is guaranteed by the documentation",
950    ),
951
952
953    // ==========================================================================
954    // Internal attributes: Type system related:
955    // ==========================================================================
956
957    gated!(fundamental, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes, experimental!(fundamental)),
958    gated!(
959        may_dangle, Normal, template!(Word), WarnFollowing,
960        EncodeCrossCrate::No, dropck_eyepatch,
961        "`may_dangle` has unstable semantics and may be removed in the future",
962    ),
963
964    rustc_attr!(
965        rustc_never_type_options,
966        Normal,
967        template!(List: &[
968            "",
969            r#"fallback = "unit""#,
970            r#"fallback = "niko""#,
971            r#"fallback = "never""#,
972            r#"fallback = "no""#,
973        ]),
974        ErrorFollowing,
975        EncodeCrossCrate::No,
976        "`rustc_never_type_options` is used to experiment with never type fallback and work on \
977         never type stabilization"
978    ),
979
980    // ==========================================================================
981    // Internal attributes: Runtime related:
982    // ==========================================================================
983
984    rustc_attr!(
985        rustc_allocator, Normal, template!(Word), WarnFollowing,
986        EncodeCrossCrate::No,
987    ),
988    rustc_attr!(
989        rustc_nounwind, Normal, template!(Word), WarnFollowing,
990        EncodeCrossCrate::No,
991    ),
992    rustc_attr!(
993        rustc_reallocator, Normal, template!(Word), WarnFollowing,
994        EncodeCrossCrate::No,
995    ),
996    rustc_attr!(
997        rustc_deallocator, Normal, template!(Word), WarnFollowing,
998        EncodeCrossCrate::No,
999    ),
1000    rustc_attr!(
1001        rustc_allocator_zeroed, Normal, template!(Word), WarnFollowing,
1002        EncodeCrossCrate::No,
1003    ),
1004    rustc_attr!(
1005        rustc_allocator_zeroed_variant, Normal, template!(NameValueStr: "function"), ErrorPreceding,
1006        EncodeCrossCrate::Yes,
1007    ),
1008    gated!(
1009        default_lib_allocator, Normal, template!(Word), WarnFollowing,
1010        EncodeCrossCrate::No, allocator_internals, experimental!(default_lib_allocator),
1011    ),
1012    gated!(
1013        needs_allocator, Normal, template!(Word), WarnFollowing,
1014        EncodeCrossCrate::No, allocator_internals, experimental!(needs_allocator),
1015    ),
1016    gated!(
1017        panic_runtime, CrateLevel, template!(Word), WarnFollowing,
1018        EncodeCrossCrate::No, experimental!(panic_runtime)
1019    ),
1020    gated!(
1021        needs_panic_runtime, CrateLevel, template!(Word), WarnFollowing,
1022        EncodeCrossCrate::No, experimental!(needs_panic_runtime)
1023    ),
1024    gated!(
1025        compiler_builtins, CrateLevel, template!(Word), WarnFollowing,
1026        EncodeCrossCrate::No,
1027        "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
1028        which contains compiler-rt intrinsics and will never be stable",
1029    ),
1030    gated!(
1031        profiler_runtime, CrateLevel, template!(Word), WarnFollowing,
1032        EncodeCrossCrate::No,
1033        "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
1034        which contains the profiler runtime and will never be stable",
1035    ),
1036
1037    // ==========================================================================
1038    // Internal attributes, Linkage:
1039    // ==========================================================================
1040
1041    gated!(
1042        linkage, Normal, template!(NameValueStr: [
1043            "available_externally",
1044            "common",
1045            "extern_weak",
1046            "external",
1047            "internal",
1048            "linkonce",
1049            "linkonce_odr",
1050            "weak",
1051            "weak_odr",
1052        ], "https://doc.rust-lang.org/reference/linkage.html"),
1053        ErrorPreceding, EncodeCrossCrate::No,
1054        "the `linkage` attribute is experimental and not portable across platforms",
1055    ),
1056    rustc_attr!(
1057        rustc_std_internal_symbol, Normal, template!(Word), WarnFollowing,
1058        EncodeCrossCrate::No,
1059    ),
1060
1061    // ==========================================================================
1062    // Internal attributes, Macro related:
1063    // ==========================================================================
1064
1065    rustc_attr!(
1066        rustc_builtin_macro, Normal,
1067        template!(Word, List: &["name", "name, /*opt*/ attributes(name1, name2, ...)"]), ErrorFollowing,
1068        EncodeCrossCrate::Yes,
1069    ),
1070    rustc_attr!(
1071        rustc_proc_macro_decls, Normal, template!(Word), WarnFollowing,
1072        EncodeCrossCrate::No,
1073    ),
1074    rustc_attr!(
1075        rustc_macro_transparency, Normal,
1076        template!(NameValueStr: ["transparent", "semiopaque", "opaque"]), ErrorFollowing,
1077        EncodeCrossCrate::Yes, "used internally for testing macro hygiene",
1078    ),
1079    rustc_attr!(
1080        rustc_autodiff, Normal,
1081        template!(Word, List: &[r#""...""#]), DuplicatesOk,
1082        EncodeCrossCrate::Yes,
1083    ),
1084    // Traces that are left when `cfg` and `cfg_attr` attributes are expanded.
1085    // The attributes are not gated, to avoid stability errors, but they cannot be used in stable
1086    // or unstable code directly because `sym::cfg_(attr_)trace` are not valid identifiers, they
1087    // can only be generated by the compiler.
1088    ungated!(
1089        cfg_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
1090        EncodeCrossCrate::No
1091    ),
1092    ungated!(
1093        cfg_attr_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
1094        EncodeCrossCrate::No
1095    ),
1096
1097    // ==========================================================================
1098    // Internal attributes, Diagnostics related:
1099    // ==========================================================================
1100
1101    rustc_attr!(
1102        rustc_on_unimplemented, Normal,
1103        template!(
1104            List: &[r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#],
1105            NameValueStr: "message"
1106        ),
1107        ErrorFollowing, EncodeCrossCrate::Yes,
1108        "see `#[diagnostic::on_unimplemented]` for the stable equivalent of this attribute"
1109    ),
1110    rustc_attr!(
1111        rustc_confusables, Normal,
1112        template!(List: &[r#""name1", "name2", ..."#]),
1113        ErrorFollowing, EncodeCrossCrate::Yes,
1114    ),
1115    // Enumerates "identity-like" conversion methods to suggest on type mismatch.
1116    rustc_attr!(
1117        rustc_conversion_suggestion, Normal, template!(Word),
1118        WarnFollowing, EncodeCrossCrate::Yes,
1119    ),
1120    // Prevents field reads in the marked trait or method to be considered
1121    // during dead code analysis.
1122    rustc_attr!(
1123        rustc_trivial_field_reads, Normal, template!(Word),
1124        WarnFollowing, EncodeCrossCrate::Yes,
1125    ),
1126    // Used by the `rustc::potential_query_instability` lint to warn methods which
1127    // might not be stable during incremental compilation.
1128    rustc_attr!(
1129        rustc_lint_query_instability, Normal, template!(Word),
1130        WarnFollowing, EncodeCrossCrate::Yes,
1131    ),
1132    // Used by the `rustc::untracked_query_information` lint to warn methods which
1133    // might not be stable during incremental compilation.
1134    rustc_attr!(
1135        rustc_lint_untracked_query_information, Normal, template!(Word),
1136        WarnFollowing, EncodeCrossCrate::Yes,
1137    ),
1138    // Used by the `rustc::diagnostic_outside_of_impl` lints to assist in changes to diagnostic
1139    // APIs. Any function with this attribute will be checked by that lint.
1140    rustc_attr!(
1141        rustc_lint_diagnostics, Normal, template!(Word),
1142        WarnFollowing, EncodeCrossCrate::Yes,
1143    ),
1144    // Used by the `rustc::bad_opt_access` lint to identify `DebuggingOptions` and `CodegenOptions`
1145    // types (as well as any others in future).
1146    rustc_attr!(
1147        rustc_lint_opt_ty, Normal, template!(Word),
1148        WarnFollowing, EncodeCrossCrate::Yes,
1149    ),
1150    // Used by the `rustc::bad_opt_access` lint on fields
1151    // types (as well as any others in future).
1152    rustc_attr!(
1153        rustc_lint_opt_deny_field_access, Normal, template!(List: &["message"]),
1154        WarnFollowing, EncodeCrossCrate::Yes,
1155    ),
1156
1157    // ==========================================================================
1158    // Internal attributes, Const related:
1159    // ==========================================================================
1160
1161    rustc_attr!(
1162        rustc_promotable, Normal, template!(Word), WarnFollowing,
1163        EncodeCrossCrate::No, ),
1164    rustc_attr!(
1165        rustc_legacy_const_generics, Normal, template!(List: &["N"]), ErrorFollowing,
1166        EncodeCrossCrate::Yes,
1167    ),
1168    // Do not const-check this function's body. It will always get replaced during CTFE via `hook_special_const_fn`.
1169    rustc_attr!(
1170        rustc_do_not_const_check, Normal, template!(Word), WarnFollowing,
1171        EncodeCrossCrate::Yes, "`#[rustc_do_not_const_check]` skips const-check for this function's body",
1172    ),
1173    rustc_attr!(
1174        rustc_const_stable_indirect, Normal,
1175        template!(Word),
1176        WarnFollowing,
1177        EncodeCrossCrate::No,
1178        "this is an internal implementation detail",
1179    ),
1180    rustc_attr!(
1181        rustc_intrinsic_const_stable_indirect, Normal,
1182        template!(Word), WarnFollowing, EncodeCrossCrate::No,  "this is an internal implementation detail",
1183    ),
1184    gated!(
1185        rustc_allow_const_fn_unstable, Normal,
1186        template!(Word, List: &["feat1, feat2, ..."]), DuplicatesOk, EncodeCrossCrate::No,
1187        "rustc_allow_const_fn_unstable side-steps feature gating and stability checks"
1188    ),
1189
1190    // ==========================================================================
1191    // Internal attributes, Layout related:
1192    // ==========================================================================
1193
1194    rustc_attr!(
1195        rustc_layout_scalar_valid_range_start, Normal, template!(List: &["value"]), ErrorFollowing,
1196        EncodeCrossCrate::Yes,
1197        "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
1198        niche optimizations in the standard library",
1199    ),
1200    rustc_attr!(
1201        rustc_layout_scalar_valid_range_end, Normal, template!(List: &["value"]), ErrorFollowing,
1202        EncodeCrossCrate::Yes,
1203        "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
1204        niche optimizations in the standard library",
1205    ),
1206    rustc_attr!(
1207        rustc_nonnull_optimization_guaranteed, Normal, template!(Word), WarnFollowing,
1208        EncodeCrossCrate::Yes,
1209        "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document \
1210        guaranteed niche optimizations in the standard library",
1211        "the compiler does not even check whether the type indeed is being non-null-optimized; \
1212        it is your responsibility to ensure that the attribute is only used on types that are optimized",
1213    ),
1214
1215    // ==========================================================================
1216    // Internal attributes, Misc:
1217    // ==========================================================================
1218    gated!(
1219        lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, EncodeCrossCrate::No, lang_items,
1220        "lang items are subject to change",
1221    ),
1222    rustc_attr!(
1223        rustc_as_ptr, Normal, template!(Word), ErrorFollowing,
1224        EncodeCrossCrate::Yes,
1225        "`#[rustc_as_ptr]` is used to mark functions returning pointers to their inner allocations."
1226    ),
1227    rustc_attr!(
1228        rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,
1229        EncodeCrossCrate::Yes,
1230        "`#[rustc_pass_by_value]` is used to mark types that must be passed by value instead of reference."
1231    ),
1232    rustc_attr!(
1233        rustc_never_returns_null_ptr, Normal, template!(Word), ErrorFollowing,
1234        EncodeCrossCrate::Yes,
1235        "`#[rustc_never_returns_null_ptr]` is used to mark functions returning non-null pointers."
1236    ),
1237    rustc_attr!(
1238        rustc_no_implicit_autorefs, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes,
1239        "`#[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."
1240    ),
1241    rustc_attr!(
1242        rustc_coherence_is_core, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1243        "`#![rustc_coherence_is_core]` allows inherent methods on builtin types, only intended to be used in `core`."
1244    ),
1245    rustc_attr!(
1246        rustc_coinductive, AttributeType::Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1247        "`#[rustc_coinductive]` changes a trait to be coinductive, allowing cycles in the trait solver."
1248    ),
1249    rustc_attr!(
1250        rustc_allow_incoherent_impl, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1251        "`#[rustc_allow_incoherent_impl]` has to be added to all impl items of an incoherent inherent impl."
1252    ),
1253    rustc_attr!(
1254        rustc_preserve_ub_checks, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1255        "`#![rustc_preserve_ub_checks]` prevents the designated crate from evaluating whether UB checks are enabled when optimizing MIR",
1256    ),
1257    rustc_attr!(
1258        rustc_deny_explicit_impl,
1259        AttributeType::Normal,
1260        template!(Word),
1261        ErrorFollowing,
1262        EncodeCrossCrate::No,
1263        "`#[rustc_deny_explicit_impl]` enforces that a trait can have no user-provided impls"
1264    ),
1265    rustc_attr!(
1266        rustc_do_not_implement_via_object,
1267        AttributeType::Normal,
1268        template!(Word),
1269        ErrorFollowing,
1270        EncodeCrossCrate::No,
1271        "`#[rustc_do_not_implement_via_object]` opts out of the automatic trait impl for trait objects \
1272        (`impl Trait for dyn Trait`)"
1273    ),
1274    rustc_attr!(
1275        rustc_has_incoherent_inherent_impls, AttributeType::Normal, template!(Word),
1276        ErrorFollowing, EncodeCrossCrate::Yes,
1277        "`#[rustc_has_incoherent_inherent_impls]` allows the addition of incoherent inherent impls for \
1278         the given type by annotating all impl items with `#[rustc_allow_incoherent_impl]`."
1279    ),
1280
1281    BuiltinAttribute {
1282        name: sym::rustc_diagnostic_item,
1283        // FIXME: This can be `true` once we always use `tcx.is_diagnostic_item`.
1284        encode_cross_crate: EncodeCrossCrate::Yes,
1285        type_: Normal,
1286        safety: AttributeSafety::Normal,
1287        template: template!(NameValueStr: "name"),
1288        duplicates: ErrorFollowing,
1289        gate: Gated{
1290            feature: sym::rustc_attrs,
1291            message: "use of an internal attribute",
1292            check: Features::rustc_attrs,
1293            notes: &["the `#[rustc_diagnostic_item]` attribute allows the compiler to reference types \
1294            from the standard library for diagnostic purposes"],
1295        },
1296    },
1297    gated!(
1298        // Used in resolve:
1299        prelude_import, Normal, template!(Word), WarnFollowing,
1300        EncodeCrossCrate::No, "`#[prelude_import]` is for use by rustc only",
1301    ),
1302    gated!(
1303        rustc_paren_sugar, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1304        unboxed_closures, "unboxed_closures are still evolving",
1305    ),
1306    rustc_attr!(
1307        rustc_inherit_overflow_checks, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1308        "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
1309        overflow checking behavior of several functions in the standard library that are inlined \
1310        across crates",
1311    ),
1312    rustc_attr!(
1313        rustc_reservation_impl, Normal,
1314        template!(NameValueStr: "reservation message"), ErrorFollowing, EncodeCrossCrate::Yes,
1315        "the `#[rustc_reservation_impl]` attribute is internally used \
1316        for reserving `impl<T> From<!> for T` as part of the effort to stabilize `!`"
1317    ),
1318    rustc_attr!(
1319        rustc_test_marker, Normal, template!(NameValueStr: "name"), WarnFollowing,
1320        EncodeCrossCrate::No, "the `#[rustc_test_marker]` attribute is used internally to track tests",
1321    ),
1322    rustc_attr!(
1323        rustc_unsafe_specialization_marker, Normal, template!(Word),
1324        WarnFollowing, EncodeCrossCrate::No,
1325        "the `#[rustc_unsafe_specialization_marker]` attribute is used to check specializations"
1326    ),
1327    rustc_attr!(
1328        rustc_specialization_trait, Normal, template!(Word),
1329        WarnFollowing, EncodeCrossCrate::No,
1330        "the `#[rustc_specialization_trait]` attribute is used to check specializations"
1331    ),
1332    rustc_attr!(
1333        rustc_main, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1334        "the `#[rustc_main]` attribute is used internally to specify test entry point function",
1335    ),
1336    rustc_attr!(
1337        rustc_skip_during_method_dispatch, Normal, template!(List: &["array, boxed_slice"]), ErrorFollowing,
1338        EncodeCrossCrate::No,
1339        "the `#[rustc_skip_during_method_dispatch]` attribute is used to exclude a trait \
1340        from method dispatch when the receiver is of the following type, for compatibility in \
1341        editions < 2021 (array) or editions < 2024 (boxed_slice)."
1342    ),
1343    rustc_attr!(
1344        rustc_must_implement_one_of, Normal, template!(List: &["function1, function2, ..."]),
1345        ErrorFollowing, EncodeCrossCrate::No,
1346        "the `#[rustc_must_implement_one_of]` attribute is used to change minimal complete \
1347        definition of a trait. Its syntax and semantics are highly experimental and will be \
1348        subject to change before stabilization",
1349    ),
1350    rustc_attr!(
1351        rustc_doc_primitive, Normal, template!(NameValueStr: "primitive name"), ErrorFollowing,
1352        EncodeCrossCrate::Yes, "the `#[rustc_doc_primitive]` attribute is used by the standard library \
1353        to provide a way to generate documentation for primitive types",
1354    ),
1355    gated!(
1356        rustc_intrinsic, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes, intrinsics,
1357        "the `#[rustc_intrinsic]` attribute is used to declare intrinsics as function items",
1358    ),
1359    rustc_attr!(
1360        rustc_no_mir_inline, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes,
1361        "`#[rustc_no_mir_inline]` prevents the MIR inliner from inlining a function while not affecting codegen"
1362    ),
1363    rustc_attr!(
1364        rustc_force_inline, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing, EncodeCrossCrate::Yes,
1365        "`#[rustc_force_inline]` forces a free function to be inlined"
1366    ),
1367
1368    // ==========================================================================
1369    // Internal attributes, Testing:
1370    // ==========================================================================
1371
1372    rustc_attr!(TEST, rustc_effective_visibility, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
1373    rustc_attr!(
1374        TEST, rustc_outlives, Normal, template!(Word),
1375        WarnFollowing, EncodeCrossCrate::No
1376    ),
1377    rustc_attr!(
1378        TEST, rustc_capture_analysis, Normal, template!(Word),
1379        WarnFollowing, EncodeCrossCrate::No
1380    ),
1381    rustc_attr!(
1382        TEST, rustc_insignificant_dtor, Normal, template!(Word),
1383        WarnFollowing, EncodeCrossCrate::Yes
1384    ),
1385    rustc_attr!(
1386        TEST, rustc_no_implicit_bounds, CrateLevel, template!(Word),
1387        WarnFollowing, EncodeCrossCrate::No
1388    ),
1389    rustc_attr!(
1390        TEST, rustc_strict_coherence, Normal, template!(Word),
1391        WarnFollowing, EncodeCrossCrate::Yes
1392    ),
1393    rustc_attr!(
1394        TEST, rustc_variance, Normal, template!(Word),
1395        WarnFollowing, EncodeCrossCrate::No
1396    ),
1397    rustc_attr!(
1398        TEST, rustc_variance_of_opaques, Normal, template!(Word),
1399        WarnFollowing, EncodeCrossCrate::No
1400    ),
1401    rustc_attr!(
1402        TEST, rustc_hidden_type_of_opaques, Normal, template!(Word),
1403        WarnFollowing, EncodeCrossCrate::No
1404    ),
1405    rustc_attr!(
1406        TEST, rustc_layout, Normal, template!(List: &["field1, field2, ..."]),
1407        WarnFollowing, EncodeCrossCrate::Yes
1408    ),
1409    rustc_attr!(
1410        TEST, rustc_abi, Normal, template!(List: &["field1, field2, ..."]),
1411        WarnFollowing, EncodeCrossCrate::No
1412    ),
1413    rustc_attr!(
1414        TEST, rustc_regions, Normal, template!(Word),
1415        WarnFollowing, EncodeCrossCrate::No
1416    ),
1417    rustc_attr!(
1418        TEST, rustc_delayed_bug_from_inside_query, Normal,
1419        template!(Word),
1420        WarnFollowing, EncodeCrossCrate::No
1421    ),
1422    rustc_attr!(
1423        TEST, rustc_dump_user_args, Normal, template!(Word),
1424        WarnFollowing, EncodeCrossCrate::No
1425    ),
1426    rustc_attr!(
1427        TEST, rustc_evaluate_where_clauses, Normal, template!(Word), WarnFollowing,
1428        EncodeCrossCrate::Yes
1429    ),
1430    rustc_attr!(
1431        TEST, rustc_if_this_changed, Normal, template!(Word, List: &["DepNode"]), DuplicatesOk,
1432        EncodeCrossCrate::No
1433    ),
1434    rustc_attr!(
1435        TEST, rustc_then_this_would_need, Normal, template!(List: &["DepNode"]), DuplicatesOk,
1436        EncodeCrossCrate::No
1437    ),
1438    rustc_attr!(
1439        TEST, rustc_clean, Normal,
1440        template!(List: &[r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#]),
1441        DuplicatesOk, EncodeCrossCrate::No
1442    ),
1443    rustc_attr!(
1444        TEST, rustc_partition_reused, Normal,
1445        template!(List: &[r#"cfg = "...", module = "...""#]), DuplicatesOk, EncodeCrossCrate::No
1446    ),
1447    rustc_attr!(
1448        TEST, rustc_partition_codegened, Normal,
1449        template!(List: &[r#"cfg = "...", module = "...""#]), DuplicatesOk, EncodeCrossCrate::No
1450    ),
1451    rustc_attr!(
1452        TEST, rustc_expected_cgu_reuse, Normal,
1453        template!(List: &[r#"cfg = "...", module = "...", kind = "...""#]), DuplicatesOk,
1454        EncodeCrossCrate::No
1455    ),
1456    rustc_attr!(
1457        TEST, rustc_symbol_name, Normal, template!(Word),
1458        WarnFollowing, EncodeCrossCrate::No
1459    ),
1460    rustc_attr!(
1461        TEST, rustc_def_path, Normal, template!(Word),
1462        WarnFollowing, EncodeCrossCrate::No
1463    ),
1464    rustc_attr!(
1465        TEST, rustc_mir, Normal, template!(List: &["arg1, arg2, ..."]),
1466        DuplicatesOk, EncodeCrossCrate::Yes
1467    ),
1468    gated!(
1469        custom_mir, Normal, template!(List: &[r#"dialect = "...", phase = "...""#]),
1470        ErrorFollowing, EncodeCrossCrate::No,
1471        "the `#[custom_mir]` attribute is just used for the Rust test suite",
1472    ),
1473    rustc_attr!(
1474        TEST, rustc_dump_item_bounds, Normal, template!(Word),
1475        WarnFollowing, EncodeCrossCrate::No
1476    ),
1477    rustc_attr!(
1478        TEST, rustc_dump_predicates, Normal, template!(Word),
1479        WarnFollowing, EncodeCrossCrate::No
1480    ),
1481    rustc_attr!(
1482        TEST, rustc_dump_def_parents, Normal, template!(Word),
1483        WarnFollowing, EncodeCrossCrate::No
1484    ),
1485    rustc_attr!(
1486        TEST, rustc_object_lifetime_default, Normal, template!(Word),
1487        WarnFollowing, EncodeCrossCrate::No
1488    ),
1489    rustc_attr!(
1490        TEST, rustc_dump_vtable, Normal, template!(Word),
1491        WarnFollowing, EncodeCrossCrate::No
1492    ),
1493    rustc_attr!(
1494        TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/),
1495        DuplicatesOk, EncodeCrossCrate::No
1496    ),
1497    rustc_attr!(
1498        TEST, pattern_complexity_limit, CrateLevel, template!(NameValueStr: "N"),
1499        ErrorFollowing, EncodeCrossCrate::No,
1500    ),
1501];
1502
1503pub fn is_builtin_attr_name(name: Symbol) -> bool {
1504    BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
1505}
1506
1507/// Whether this builtin attribute is encoded cross crate.
1508/// This means it can be used cross crate.
1509pub fn encode_cross_crate(name: Symbol) -> bool {
1510    if let Some(attr) = BUILTIN_ATTRIBUTE_MAP.get(&name) {
1511        attr.encode_cross_crate == EncodeCrossCrate::Yes
1512    } else {
1513        true
1514    }
1515}
1516
1517pub fn is_valid_for_get_attr(name: Symbol) -> bool {
1518    BUILTIN_ATTRIBUTE_MAP.get(&name).is_some_and(|attr| match attr.duplicates {
1519        WarnFollowing | ErrorFollowing | ErrorPreceding | FutureWarnFollowing
1520        | FutureWarnPreceding => true,
1521        DuplicatesOk | WarnFollowingWordOnly => false,
1522    })
1523}
1524
1525pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>> =
1526    LazyLock::new(|| {
1527        let mut map = FxHashMap::default();
1528        for attr in BUILTIN_ATTRIBUTES.iter() {
1529            if map.insert(attr.name, attr).is_some() {
1530                panic!("duplicate builtin attribute `{}`", attr.name);
1531            }
1532        }
1533        map
1534    });
1535
1536pub fn is_stable_diagnostic_attribute(sym: Symbol, _features: &Features) -> bool {
1537    match sym {
1538        sym::on_unimplemented | sym::do_not_recommend => true,
1539        _ => false,
1540    }
1541}
rustc_feature/builtin_attrs.rs

rustc_feature/
builtin_attrs.rs
