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    ungated!(
625        unsafe(Edition2024) export_name, Normal,
626        template!(NameValueStr: "name", "https://doc.rust-lang.org/reference/abi.html#the-export_name-attribute"),
627        FutureWarnPreceding, EncodeCrossCrate::No
628    ),
629    ungated!(
630        unsafe(Edition2024) link_section, Normal,
631        template!(NameValueStr: "name", "https://doc.rust-lang.org/reference/abi.html#the-link_section-attribute"),
632        FutureWarnPreceding, EncodeCrossCrate::No
633    ),
634    ungated!(
635        unsafe(Edition2024) no_mangle, Normal,
636        template!(Word, "https://doc.rust-lang.org/reference/abi.html#the-no_mangle-attribute"),
637        WarnFollowing, EncodeCrossCrate::No
638    ),
639    ungated!(
640        used, Normal,
641        template!(Word, List: &["compiler", "linker"], "https://doc.rust-lang.org/reference/abi.html#the-used-attribute"),
642        WarnFollowing, EncodeCrossCrate::No
643    ),
644    ungated!(
645        link_ordinal, Normal,
646        template!(List: &["ordinal"], "https://doc.rust-lang.org/reference/items/external-blocks.html#the-link_ordinal-attribute"),
647        ErrorPreceding, EncodeCrossCrate::Yes
648    ),
649    ungated!(
650        unsafe naked, Normal,
651        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-naked-attribute"),
652        WarnFollowing, EncodeCrossCrate::No
653    ),
654
655    // Limits:
656    ungated!(
657        recursion_limit, CrateLevel,
658        template!(NameValueStr: "N", "https://doc.rust-lang.org/reference/attributes/limits.html#the-recursion_limit-attribute"),
659        FutureWarnFollowing, EncodeCrossCrate::No
660    ),
661    ungated!(
662        type_length_limit, CrateLevel,
663        template!(NameValueStr: "N", "https://doc.rust-lang.org/reference/attributes/limits.html#the-type_length_limit-attribute"),
664        FutureWarnFollowing, EncodeCrossCrate::No
665    ),
666    gated!(
667        move_size_limit, CrateLevel, template!(NameValueStr: "N"), ErrorFollowing,
668        EncodeCrossCrate::No, large_assignments, experimental!(move_size_limit)
669    ),
670
671    // Entry point:
672    ungated!(
673        no_main, CrateLevel,
674        template!(Word, "https://doc.rust-lang.org/reference/crates-and-source-files.html#the-no_main-attribute"),
675        WarnFollowing, EncodeCrossCrate::No
676    ),
677
678    // Modules, prelude, and resolution:
679    ungated!(
680        path, Normal,
681        template!(NameValueStr: "file", "https://doc.rust-lang.org/reference/items/modules.html#the-path-attribute"),
682        FutureWarnFollowing, EncodeCrossCrate::No
683    ),
684    ungated!(
685        no_std, CrateLevel,
686        template!(Word, "https://doc.rust-lang.org/reference/names/preludes.html#the-no_std-attribute"),
687        WarnFollowing, EncodeCrossCrate::No
688    ),
689    ungated!(
690        no_implicit_prelude, Normal,
691        template!(Word, "https://doc.rust-lang.org/reference/names/preludes.html#the-no_implicit_prelude-attribute"),
692        WarnFollowing, EncodeCrossCrate::No
693    ),
694    ungated!(
695        non_exhaustive, Normal,
696        template!(Word, "https://doc.rust-lang.org/reference/attributes/type_system.html#the-non_exhaustive-attribute"),
697        WarnFollowing, EncodeCrossCrate::Yes
698    ),
699
700    // Runtime
701    ungated!(
702        windows_subsystem, CrateLevel,
703        template!(NameValueStr: ["windows", "console"], "https://doc.rust-lang.org/reference/runtime.html#the-windows_subsystem-attribute"),
704        FutureWarnFollowing, EncodeCrossCrate::No
705    ),
706    ungated!( // RFC 2070
707        panic_handler, Normal,
708        template!(Word, "https://doc.rust-lang.org/reference/panic.html#the-panic_handler-attribute"),
709        WarnFollowing, EncodeCrossCrate::Yes
710    ),
711
712    // Code generation:
713    ungated!(
714        inline, Normal,
715        template!(
716            Word,
717            List: &["always", "never"],
718            "https://doc.rust-lang.org/reference/attributes/codegen.html#the-inline-attribute"
719        ),
720        FutureWarnFollowing, EncodeCrossCrate::No
721    ),
722    ungated!(
723        cold, Normal,
724        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-cold-attribute"),
725        WarnFollowing, EncodeCrossCrate::No
726    ),
727    ungated!(
728        no_builtins, CrateLevel,
729        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-no_builtins-attribute"),
730        WarnFollowing, EncodeCrossCrate::Yes
731    ),
732    ungated!(
733        target_feature, Normal,
734        template!(List: &[r#"enable = "name""#], "https://doc.rust-lang.org/reference/attributes/codegen.html#the-target_feature-attribute"),
735        DuplicatesOk, EncodeCrossCrate::No,
736    ),
737    ungated!(
738        track_caller, Normal,
739        template!(Word, "https://doc.rust-lang.org/reference/attributes/codegen.html#the-track_caller-attribute"),
740        WarnFollowing, EncodeCrossCrate::Yes
741    ),
742    ungated!(
743        instruction_set, Normal,
744        template!(List: &["set"], "https://doc.rust-lang.org/reference/attributes/codegen.html#the-instruction_set-attribute"),
745        ErrorPreceding, EncodeCrossCrate::No
746    ),
747    gated!(
748        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,
749        EncodeCrossCrate::No, sanitize, experimental!(sanitize),
750    ),
751    gated!(
752        coverage, Normal, template!(OneOf: &[sym::off, sym::on]),
753        ErrorPreceding, EncodeCrossCrate::No,
754        coverage_attribute, experimental!(coverage)
755    ),
756
757    ungated!(
758        doc, Normal,
759        template!(
760            List: &["hidden", "inline"],
761            NameValueStr: "string",
762            "https://doc.rust-lang.org/rustdoc/write-documentation/the-doc-attribute.html"
763        ),
764        DuplicatesOk, EncodeCrossCrate::Yes
765    ),
766
767    // Debugging
768    ungated!(
769        debugger_visualizer, Normal,
770        template!(
771            List: &[r#"natvis_file = "...", gdb_script_file = "...""#],
772            "https://doc.rust-lang.org/reference/attributes/debugger.html#the-debugger_visualizer-attribute"
773        ),
774        DuplicatesOk, EncodeCrossCrate::No
775    ),
776    ungated!(
777        collapse_debuginfo, Normal,
778        template!(
779            List: &["no", "external", "yes"],
780            "https://doc.rust-lang.org/reference/attributes/debugger.html#the-collapse_debuginfo-attribute"
781        ),
782        ErrorFollowing, EncodeCrossCrate::Yes
783    ),
784
785    // ==========================================================================
786    // Unstable attributes:
787    // ==========================================================================
788
789    // Linking:
790    gated!(
791        export_stable, Normal, template!(Word), WarnFollowing,
792        EncodeCrossCrate::No, experimental!(export_stable)
793    ),
794
795    // Testing:
796    gated!(
797        test_runner, CrateLevel, template!(List: &["path"]), ErrorFollowing,
798        EncodeCrossCrate::Yes, custom_test_frameworks,
799        "custom test frameworks are an unstable feature",
800    ),
801    // RFC #1268
802    gated!(
803        marker, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
804        marker_trait_attr, experimental!(marker)
805    ),
806    gated!(
807        thread_local, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
808        "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
809    ),
810    gated!(
811        no_core, CrateLevel, template!(Word), WarnFollowing,
812        EncodeCrossCrate::No, experimental!(no_core)
813    ),
814    // RFC 2412
815    gated!(
816        optimize, Normal, template!(List: &["none", "size", "speed"]), ErrorPreceding,
817        EncodeCrossCrate::No, optimize_attribute, experimental!(optimize)
818    ),
819
820    gated!(
821        unsafe ffi_pure, Normal, template!(Word), WarnFollowing,
822        EncodeCrossCrate::No, experimental!(ffi_pure)
823    ),
824    gated!(
825        unsafe ffi_const, Normal, template!(Word), WarnFollowing,
826        EncodeCrossCrate::No, experimental!(ffi_const)
827    ),
828    gated!(
829        register_tool, CrateLevel, template!(List: &["tool1, tool2, ..."]), DuplicatesOk,
830        EncodeCrossCrate::No, experimental!(register_tool),
831    ),
832
833    // RFC 2632
834    // FIXME(const_trait_impl) remove this
835    gated!(
836        const_trait, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No, const_trait_impl,
837        "`const_trait` is a temporary placeholder for marking a trait that is suitable for `const` \
838        `impls` and all default bodies as `const`, which may be removed or renamed in the \
839        future."
840    ),
841    // lang-team MCP 147
842    gated!(
843        deprecated_safe, Normal, template!(List: &[r#"since = "version", note = "...""#]), ErrorFollowing,
844        EncodeCrossCrate::Yes, experimental!(deprecated_safe),
845    ),
846
847    // `#[cfi_encoding = ""]`
848    gated!(
849        cfi_encoding, Normal, template!(NameValueStr: "encoding"), ErrorPreceding,
850        EncodeCrossCrate::Yes, experimental!(cfi_encoding)
851    ),
852
853    // `#[coroutine]` attribute to be applied to closures to make them coroutines instead
854    gated!(
855        coroutine, Normal, template!(Word), ErrorFollowing,
856        EncodeCrossCrate::No, coroutines, experimental!(coroutine)
857    ),
858
859    // RFC 3543
860    // `#[patchable_function_entry(prefix_nops = m, entry_nops = n)]`
861    gated!(
862        patchable_function_entry, Normal, template!(List: &["prefix_nops = m, entry_nops = n"]), ErrorPreceding,
863        EncodeCrossCrate::Yes, experimental!(patchable_function_entry)
864    ),
865
866    // Probably temporary component of min_generic_const_args.
867    // `#[type_const] const ASSOC: usize;`
868    gated!(
869        type_const, Normal, template!(Word), ErrorFollowing,
870        EncodeCrossCrate::Yes, min_generic_const_args, experimental!(type_const),
871    ),
872
873    // The `#[loop_match]` and `#[const_continue]` attributes are part of the
874    // lang experiment for RFC 3720 tracked in:
875    //
876    // - https://github.com/rust-lang/rust/issues/132306
877    gated!(
878        const_continue, Normal, template!(Word), ErrorFollowing,
879        EncodeCrossCrate::No, loop_match, experimental!(const_continue)
880    ),
881    gated!(
882        loop_match, Normal, template!(Word), ErrorFollowing,
883        EncodeCrossCrate::No, loop_match, experimental!(loop_match)
884    ),
885
886    // ==========================================================================
887    // Internal attributes: Stability, deprecation, and unsafe:
888    // ==========================================================================
889
890    ungated!(
891        feature, CrateLevel,
892        template!(List: &["name1, name2, ..."]), DuplicatesOk, EncodeCrossCrate::No,
893    ),
894    // DuplicatesOk since it has its own validation
895    ungated!(
896        stable, Normal,
897        template!(List: &[r#"feature = "name", since = "version""#]), DuplicatesOk, EncodeCrossCrate::No,
898    ),
899    ungated!(
900        unstable, Normal,
901        template!(List: &[r#"feature = "name", reason = "...", issue = "N""#]), DuplicatesOk,
902        EncodeCrossCrate::Yes
903    ),
904    ungated!(
905        unstable_feature_bound, Normal, template!(Word, List: &["feat1, feat2, ..."]),
906        DuplicatesOk, EncodeCrossCrate::No,
907    ),
908    ungated!(
909        rustc_const_unstable, Normal, template!(List: &[r#"feature = "name""#]),
910        DuplicatesOk, EncodeCrossCrate::Yes
911    ),
912    ungated!(
913        rustc_const_stable, Normal,
914        template!(List: &[r#"feature = "name""#]), DuplicatesOk, EncodeCrossCrate::No,
915    ),
916    ungated!(
917        rustc_default_body_unstable, Normal,
918        template!(List: &[r#"feature = "name", reason = "...", issue = "N""#]),
919        DuplicatesOk, EncodeCrossCrate::No
920    ),
921    gated!(
922        allow_internal_unstable, Normal, template!(Word, List: &["feat1, feat2, ..."]),
923        DuplicatesOk, EncodeCrossCrate::Yes,
924        "allow_internal_unstable side-steps feature gating and stability checks",
925    ),
926    gated!(
927        allow_internal_unsafe, Normal, template!(Word), WarnFollowing,
928        EncodeCrossCrate::No, "allow_internal_unsafe side-steps the unsafe_code lint",
929    ),
930    rustc_attr!(
931        rustc_allowed_through_unstable_modules, Normal, template!(NameValueStr: "deprecation message"),
932        WarnFollowing, EncodeCrossCrate::No,
933        "rustc_allowed_through_unstable_modules special cases accidental stabilizations of stable items \
934        through unstable paths"
935    ),
936    rustc_attr!(
937        rustc_deprecated_safe_2024, Normal, template!(List: &[r#"audit_that = "...""#]),
938        ErrorFollowing, EncodeCrossCrate::Yes,
939        "`#[rustc_deprecated_safe_2024]` is used to declare functions unsafe across the edition 2024 boundary",
940    ),
941    rustc_attr!(
942        rustc_pub_transparent, Normal, template!(Word),
943        ErrorFollowing, EncodeCrossCrate::Yes,
944        "used internally to mark types with a `transparent` representation when it is guaranteed by the documentation",
945    ),
946
947
948    // ==========================================================================
949    // Internal attributes: Type system related:
950    // ==========================================================================
951
952    gated!(fundamental, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes, experimental!(fundamental)),
953    gated!(
954        may_dangle, Normal, template!(Word), WarnFollowing,
955        EncodeCrossCrate::No, dropck_eyepatch,
956        "`may_dangle` has unstable semantics and may be removed in the future",
957    ),
958
959    rustc_attr!(
960        rustc_never_type_options,
961        Normal,
962        template!(List: &[
963            "",
964            r#"fallback = "unit""#,
965            r#"fallback = "niko""#,
966            r#"fallback = "never""#,
967            r#"fallback = "no""#,
968        ]),
969        ErrorFollowing,
970        EncodeCrossCrate::No,
971        "`rustc_never_type_options` is used to experiment with never type fallback and work on \
972         never type stabilization"
973    ),
974
975    // ==========================================================================
976    // Internal attributes: Runtime related:
977    // ==========================================================================
978
979    rustc_attr!(
980        rustc_allocator, Normal, template!(Word), WarnFollowing,
981        EncodeCrossCrate::No,
982    ),
983    rustc_attr!(
984        rustc_nounwind, Normal, template!(Word), WarnFollowing,
985        EncodeCrossCrate::No,
986    ),
987    rustc_attr!(
988        rustc_reallocator, Normal, template!(Word), WarnFollowing,
989        EncodeCrossCrate::No,
990    ),
991    rustc_attr!(
992        rustc_deallocator, Normal, template!(Word), WarnFollowing,
993        EncodeCrossCrate::No,
994    ),
995    rustc_attr!(
996        rustc_allocator_zeroed, Normal, template!(Word), WarnFollowing,
997        EncodeCrossCrate::No,
998    ),
999    gated!(
1000        default_lib_allocator, Normal, template!(Word), WarnFollowing,
1001        EncodeCrossCrate::No, allocator_internals, experimental!(default_lib_allocator),
1002    ),
1003    gated!(
1004        needs_allocator, Normal, template!(Word), WarnFollowing,
1005        EncodeCrossCrate::No, allocator_internals, experimental!(needs_allocator),
1006    ),
1007    gated!(
1008        panic_runtime, CrateLevel, template!(Word), WarnFollowing,
1009        EncodeCrossCrate::No, experimental!(panic_runtime)
1010    ),
1011    gated!(
1012        needs_panic_runtime, CrateLevel, template!(Word), WarnFollowing,
1013        EncodeCrossCrate::No, experimental!(needs_panic_runtime)
1014    ),
1015    gated!(
1016        compiler_builtins, CrateLevel, template!(Word), WarnFollowing,
1017        EncodeCrossCrate::No,
1018        "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
1019        which contains compiler-rt intrinsics and will never be stable",
1020    ),
1021    gated!(
1022        profiler_runtime, CrateLevel, template!(Word), WarnFollowing,
1023        EncodeCrossCrate::No,
1024        "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
1025        which contains the profiler runtime and will never be stable",
1026    ),
1027
1028    // ==========================================================================
1029    // Internal attributes, Linkage:
1030    // ==========================================================================
1031
1032    gated!(
1033        linkage, Normal, template!(NameValueStr: [
1034            "available_externally",
1035            "common",
1036            "extern_weak",
1037            "external",
1038            "internal",
1039            "linkonce",
1040            "linkonce_odr",
1041            "weak",
1042            "weak_odr",
1043        ], "https://doc.rust-lang.org/reference/linkage.html"),
1044        ErrorPreceding, EncodeCrossCrate::No,
1045        "the `linkage` attribute is experimental and not portable across platforms",
1046    ),
1047    rustc_attr!(
1048        rustc_std_internal_symbol, Normal, template!(Word), WarnFollowing,
1049        EncodeCrossCrate::No,
1050    ),
1051
1052    // ==========================================================================
1053    // Internal attributes, Macro related:
1054    // ==========================================================================
1055
1056    rustc_attr!(
1057        rustc_builtin_macro, Normal,
1058        template!(Word, List: &["name", "name, /*opt*/ attributes(name1, name2, ...)"]), ErrorFollowing,
1059        EncodeCrossCrate::Yes,
1060    ),
1061    rustc_attr!(
1062        rustc_proc_macro_decls, Normal, template!(Word), WarnFollowing,
1063        EncodeCrossCrate::No,
1064    ),
1065    rustc_attr!(
1066        rustc_macro_transparency, Normal,
1067        template!(NameValueStr: ["transparent", "semiopaque", "opaque"]), ErrorFollowing,
1068        EncodeCrossCrate::Yes, "used internally for testing macro hygiene",
1069    ),
1070    rustc_attr!(
1071        rustc_autodiff, Normal,
1072        template!(Word, List: &[r#""...""#]), DuplicatesOk,
1073        EncodeCrossCrate::Yes,
1074    ),
1075    // Traces that are left when `cfg` and `cfg_attr` attributes are expanded.
1076    // The attributes are not gated, to avoid stability errors, but they cannot be used in stable
1077    // or unstable code directly because `sym::cfg_(attr_)trace` are not valid identifiers, they
1078    // can only be generated by the compiler.
1079    ungated!(
1080        cfg_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
1081        EncodeCrossCrate::No
1082    ),
1083    ungated!(
1084        cfg_attr_trace, Normal, template!(Word /* irrelevant */), DuplicatesOk,
1085        EncodeCrossCrate::No
1086    ),
1087
1088    // ==========================================================================
1089    // Internal attributes, Diagnostics related:
1090    // ==========================================================================
1091
1092    rustc_attr!(
1093        rustc_on_unimplemented, Normal,
1094        template!(
1095            List: &[r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#],
1096            NameValueStr: "message"
1097        ),
1098        ErrorFollowing, EncodeCrossCrate::Yes,
1099        "see `#[diagnostic::on_unimplemented]` for the stable equivalent of this attribute"
1100    ),
1101    rustc_attr!(
1102        rustc_confusables, Normal,
1103        template!(List: &[r#""name1", "name2", ..."#]),
1104        ErrorFollowing, EncodeCrossCrate::Yes,
1105    ),
1106    // Enumerates "identity-like" conversion methods to suggest on type mismatch.
1107    rustc_attr!(
1108        rustc_conversion_suggestion, Normal, template!(Word),
1109        WarnFollowing, EncodeCrossCrate::Yes,
1110    ),
1111    // Prevents field reads in the marked trait or method to be considered
1112    // during dead code analysis.
1113    rustc_attr!(
1114        rustc_trivial_field_reads, Normal, template!(Word),
1115        WarnFollowing, EncodeCrossCrate::Yes,
1116    ),
1117    // Used by the `rustc::potential_query_instability` lint to warn methods which
1118    // might not be stable during incremental compilation.
1119    rustc_attr!(
1120        rustc_lint_query_instability, Normal, template!(Word),
1121        WarnFollowing, EncodeCrossCrate::Yes,
1122    ),
1123    // Used by the `rustc::untracked_query_information` lint to warn methods which
1124    // might not be stable during incremental compilation.
1125    rustc_attr!(
1126        rustc_lint_untracked_query_information, Normal, template!(Word),
1127        WarnFollowing, EncodeCrossCrate::Yes,
1128    ),
1129    // Used by the `rustc::diagnostic_outside_of_impl` lints to assist in changes to diagnostic
1130    // APIs. Any function with this attribute will be checked by that lint.
1131    rustc_attr!(
1132        rustc_lint_diagnostics, Normal, template!(Word),
1133        WarnFollowing, EncodeCrossCrate::Yes,
1134    ),
1135    // Used by the `rustc::bad_opt_access` lint to identify `DebuggingOptions` and `CodegenOptions`
1136    // types (as well as any others in future).
1137    rustc_attr!(
1138        rustc_lint_opt_ty, Normal, template!(Word),
1139        WarnFollowing, EncodeCrossCrate::Yes,
1140    ),
1141    // Used by the `rustc::bad_opt_access` lint on fields
1142    // types (as well as any others in future).
1143    rustc_attr!(
1144        rustc_lint_opt_deny_field_access, Normal, template!(List: &["message"]),
1145        WarnFollowing, EncodeCrossCrate::Yes,
1146    ),
1147
1148    // ==========================================================================
1149    // Internal attributes, Const related:
1150    // ==========================================================================
1151
1152    rustc_attr!(
1153        rustc_promotable, Normal, template!(Word), WarnFollowing,
1154        EncodeCrossCrate::No, ),
1155    rustc_attr!(
1156        rustc_legacy_const_generics, Normal, template!(List: &["N"]), ErrorFollowing,
1157        EncodeCrossCrate::Yes,
1158    ),
1159    // Do not const-check this function's body. It will always get replaced during CTFE via `hook_special_const_fn`.
1160    rustc_attr!(
1161        rustc_do_not_const_check, Normal, template!(Word), WarnFollowing,
1162        EncodeCrossCrate::Yes, "`#[rustc_do_not_const_check]` skips const-check for this function's body",
1163    ),
1164    rustc_attr!(
1165        rustc_const_stable_indirect, Normal,
1166        template!(Word),
1167        WarnFollowing,
1168        EncodeCrossCrate::No,
1169        "this is an internal implementation detail",
1170    ),
1171    rustc_attr!(
1172        rustc_intrinsic_const_stable_indirect, Normal,
1173        template!(Word), WarnFollowing, EncodeCrossCrate::No,  "this is an internal implementation detail",
1174    ),
1175    gated!(
1176        rustc_allow_const_fn_unstable, Normal,
1177        template!(Word, List: &["feat1, feat2, ..."]), DuplicatesOk, EncodeCrossCrate::No,
1178        "rustc_allow_const_fn_unstable side-steps feature gating and stability checks"
1179    ),
1180
1181    // ==========================================================================
1182    // Internal attributes, Layout related:
1183    // ==========================================================================
1184
1185    rustc_attr!(
1186        rustc_layout_scalar_valid_range_start, Normal, template!(List: &["value"]), ErrorFollowing,
1187        EncodeCrossCrate::Yes,
1188        "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
1189        niche optimizations in the standard library",
1190    ),
1191    rustc_attr!(
1192        rustc_layout_scalar_valid_range_end, Normal, template!(List: &["value"]), ErrorFollowing,
1193        EncodeCrossCrate::Yes,
1194        "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
1195        niche optimizations in the standard library",
1196    ),
1197    rustc_attr!(
1198        rustc_nonnull_optimization_guaranteed, Normal, template!(Word), WarnFollowing,
1199        EncodeCrossCrate::Yes,
1200        "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to document \
1201        guaranteed niche optimizations in the standard library",
1202        "the compiler does not even check whether the type indeed is being non-null-optimized; \
1203        it is your responsibility to ensure that the attribute is only used on types that are optimized",
1204    ),
1205
1206    // ==========================================================================
1207    // Internal attributes, Misc:
1208    // ==========================================================================
1209    gated!(
1210        lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, EncodeCrossCrate::No, lang_items,
1211        "lang items are subject to change",
1212    ),
1213    rustc_attr!(
1214        rustc_as_ptr, Normal, template!(Word), ErrorFollowing,
1215        EncodeCrossCrate::Yes,
1216        "`#[rustc_as_ptr]` is used to mark functions returning pointers to their inner allocations."
1217    ),
1218    rustc_attr!(
1219        rustc_pass_by_value, Normal, template!(Word), ErrorFollowing,
1220        EncodeCrossCrate::Yes,
1221        "`#[rustc_pass_by_value]` is used to mark types that must be passed by value instead of reference."
1222    ),
1223    rustc_attr!(
1224        rustc_never_returns_null_ptr, Normal, template!(Word), ErrorFollowing,
1225        EncodeCrossCrate::Yes,
1226        "`#[rustc_never_returns_null_ptr]` is used to mark functions returning non-null pointers."
1227    ),
1228    rustc_attr!(
1229        rustc_no_implicit_autorefs, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes,
1230        "`#[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."
1231    ),
1232    rustc_attr!(
1233        rustc_coherence_is_core, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1234        "`#![rustc_coherence_is_core]` allows inherent methods on builtin types, only intended to be used in `core`."
1235    ),
1236    rustc_attr!(
1237        rustc_coinductive, AttributeType::Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1238        "`#[rustc_coinductive]` changes a trait to be coinductive, allowing cycles in the trait solver."
1239    ),
1240    rustc_attr!(
1241        rustc_allow_incoherent_impl, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1242        "`#[rustc_allow_incoherent_impl]` has to be added to all impl items of an incoherent inherent impl."
1243    ),
1244    rustc_attr!(
1245        rustc_preserve_ub_checks, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
1246        "`#![rustc_preserve_ub_checks]` prevents the designated crate from evaluating whether UB checks are enabled when optimizing MIR",
1247    ),
1248    rustc_attr!(
1249        rustc_deny_explicit_impl,
1250        AttributeType::Normal,
1251        template!(Word),
1252        ErrorFollowing,
1253        EncodeCrossCrate::No,
1254        "`#[rustc_deny_explicit_impl]` enforces that a trait can have no user-provided impls"
1255    ),
1256    rustc_attr!(
1257        rustc_do_not_implement_via_object,
1258        AttributeType::Normal,
1259        template!(Word),
1260        ErrorFollowing,
1261        EncodeCrossCrate::No,
1262        "`#[rustc_do_not_implement_via_object]` opts out of the automatic trait impl for trait objects \
1263        (`impl Trait for dyn Trait`)"
1264    ),
1265    rustc_attr!(
1266        rustc_has_incoherent_inherent_impls, AttributeType::Normal, template!(Word),
1267        ErrorFollowing, EncodeCrossCrate::Yes,
1268        "`#[rustc_has_incoherent_inherent_impls]` allows the addition of incoherent inherent impls for \
1269         the given type by annotating all impl items with `#[rustc_allow_incoherent_impl]`."
1270    ),
1271
1272    BuiltinAttribute {
1273        name: sym::rustc_diagnostic_item,
1274        // FIXME: This can be `true` once we always use `tcx.is_diagnostic_item`.
1275        encode_cross_crate: EncodeCrossCrate::Yes,
1276        type_: Normal,
1277        safety: AttributeSafety::Normal,
1278        template: template!(NameValueStr: "name"),
1279        duplicates: ErrorFollowing,
1280        gate: Gated{
1281            feature: sym::rustc_attrs,
1282            message: "use of an internal attribute",
1283            check: Features::rustc_attrs,
1284            notes: &["the `#[rustc_diagnostic_item]` attribute allows the compiler to reference types \
1285            from the standard library for diagnostic purposes"],
1286        },
1287    },
1288    gated!(
1289        // Used in resolve:
1290        prelude_import, Normal, template!(Word), WarnFollowing,
1291        EncodeCrossCrate::No, "`#[prelude_import]` is for use by rustc only",
1292    ),
1293    gated!(
1294        rustc_paren_sugar, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1295        unboxed_closures, "unboxed_closures are still evolving",
1296    ),
1297    rustc_attr!(
1298        rustc_inherit_overflow_checks, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1299        "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
1300        overflow checking behavior of several functions in the standard library that are inlined \
1301        across crates",
1302    ),
1303    rustc_attr!(
1304        rustc_reservation_impl, Normal,
1305        template!(NameValueStr: "reservation message"), ErrorFollowing, EncodeCrossCrate::Yes,
1306        "the `#[rustc_reservation_impl]` attribute is internally used \
1307        for reserving `impl<T> From<!> for T` as part of the effort to stabilize `!`"
1308    ),
1309    rustc_attr!(
1310        rustc_test_marker, Normal, template!(NameValueStr: "name"), WarnFollowing,
1311        EncodeCrossCrate::No, "the `#[rustc_test_marker]` attribute is used internally to track tests",
1312    ),
1313    rustc_attr!(
1314        rustc_unsafe_specialization_marker, Normal, template!(Word),
1315        WarnFollowing, EncodeCrossCrate::No,
1316        "the `#[rustc_unsafe_specialization_marker]` attribute is used to check specializations"
1317    ),
1318    rustc_attr!(
1319        rustc_specialization_trait, Normal, template!(Word),
1320        WarnFollowing, EncodeCrossCrate::No,
1321        "the `#[rustc_specialization_trait]` attribute is used to check specializations"
1322    ),
1323    rustc_attr!(
1324        rustc_main, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No,
1325        "the `#[rustc_main]` attribute is used internally to specify test entry point function",
1326    ),
1327    rustc_attr!(
1328        rustc_skip_during_method_dispatch, Normal, template!(List: &["array, boxed_slice"]), ErrorFollowing,
1329        EncodeCrossCrate::No,
1330        "the `#[rustc_skip_during_method_dispatch]` attribute is used to exclude a trait \
1331        from method dispatch when the receiver is of the following type, for compatibility in \
1332        editions < 2021 (array) or editions < 2024 (boxed_slice)."
1333    ),
1334    rustc_attr!(
1335        rustc_must_implement_one_of, Normal, template!(List: &["function1, function2, ..."]),
1336        ErrorFollowing, EncodeCrossCrate::No,
1337        "the `#[rustc_must_implement_one_of]` attribute is used to change minimal complete \
1338        definition of a trait. Its syntax and semantics are highly experimental and will be \
1339        subject to change before stabilization",
1340    ),
1341    rustc_attr!(
1342        rustc_doc_primitive, Normal, template!(NameValueStr: "primitive name"), ErrorFollowing,
1343        EncodeCrossCrate::Yes, "the `#[rustc_doc_primitive]` attribute is used by the standard library \
1344        to provide a way to generate documentation for primitive types",
1345    ),
1346    gated!(
1347        rustc_intrinsic, Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes, intrinsics,
1348        "the `#[rustc_intrinsic]` attribute is used to declare intrinsics as function items",
1349    ),
1350    rustc_attr!(
1351        rustc_no_mir_inline, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes,
1352        "`#[rustc_no_mir_inline]` prevents the MIR inliner from inlining a function while not affecting codegen"
1353    ),
1354    rustc_attr!(
1355        rustc_force_inline, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing, EncodeCrossCrate::Yes,
1356        "`#[rustc_force_inline]` forces a free function to be inlined"
1357    ),
1358
1359    // ==========================================================================
1360    // Internal attributes, Testing:
1361    // ==========================================================================
1362
1363    rustc_attr!(TEST, rustc_effective_visibility, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::Yes),
1364    rustc_attr!(
1365        TEST, rustc_outlives, Normal, template!(Word),
1366        WarnFollowing, EncodeCrossCrate::No
1367    ),
1368    rustc_attr!(
1369        TEST, rustc_capture_analysis, Normal, template!(Word),
1370        WarnFollowing, EncodeCrossCrate::No
1371    ),
1372    rustc_attr!(
1373        TEST, rustc_insignificant_dtor, Normal, template!(Word),
1374        WarnFollowing, EncodeCrossCrate::Yes
1375    ),
1376    rustc_attr!(
1377        TEST, rustc_no_implicit_bounds, CrateLevel, template!(Word),
1378        WarnFollowing, EncodeCrossCrate::No
1379    ),
1380    rustc_attr!(
1381        TEST, rustc_strict_coherence, Normal, template!(Word),
1382        WarnFollowing, EncodeCrossCrate::Yes
1383    ),
1384    rustc_attr!(
1385        TEST, rustc_variance, Normal, template!(Word),
1386        WarnFollowing, EncodeCrossCrate::No
1387    ),
1388    rustc_attr!(
1389        TEST, rustc_variance_of_opaques, Normal, template!(Word),
1390        WarnFollowing, EncodeCrossCrate::No
1391    ),
1392    rustc_attr!(
1393        TEST, rustc_hidden_type_of_opaques, Normal, template!(Word),
1394        WarnFollowing, EncodeCrossCrate::No
1395    ),
1396    rustc_attr!(
1397        TEST, rustc_layout, Normal, template!(List: &["field1, field2, ..."]),
1398        WarnFollowing, EncodeCrossCrate::Yes
1399    ),
1400    rustc_attr!(
1401        TEST, rustc_abi, Normal, template!(List: &["field1, field2, ..."]),
1402        WarnFollowing, EncodeCrossCrate::No
1403    ),
1404    rustc_attr!(
1405        TEST, rustc_regions, Normal, template!(Word),
1406        WarnFollowing, EncodeCrossCrate::No
1407    ),
1408    rustc_attr!(
1409        TEST, rustc_delayed_bug_from_inside_query, Normal,
1410        template!(Word),
1411        WarnFollowing, EncodeCrossCrate::No
1412    ),
1413    rustc_attr!(
1414        TEST, rustc_dump_user_args, Normal, template!(Word),
1415        WarnFollowing, EncodeCrossCrate::No
1416    ),
1417    rustc_attr!(
1418        TEST, rustc_evaluate_where_clauses, Normal, template!(Word), WarnFollowing,
1419        EncodeCrossCrate::Yes
1420    ),
1421    rustc_attr!(
1422        TEST, rustc_if_this_changed, Normal, template!(Word, List: &["DepNode"]), DuplicatesOk,
1423        EncodeCrossCrate::No
1424    ),
1425    rustc_attr!(
1426        TEST, rustc_then_this_would_need, Normal, template!(List: &["DepNode"]), DuplicatesOk,
1427        EncodeCrossCrate::No
1428    ),
1429    rustc_attr!(
1430        TEST, rustc_clean, Normal,
1431        template!(List: &[r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#]),
1432        DuplicatesOk, EncodeCrossCrate::No
1433    ),
1434    rustc_attr!(
1435        TEST, rustc_partition_reused, Normal,
1436        template!(List: &[r#"cfg = "...", module = "...""#]), DuplicatesOk, EncodeCrossCrate::No
1437    ),
1438    rustc_attr!(
1439        TEST, rustc_partition_codegened, Normal,
1440        template!(List: &[r#"cfg = "...", module = "...""#]), DuplicatesOk, EncodeCrossCrate::No
1441    ),
1442    rustc_attr!(
1443        TEST, rustc_expected_cgu_reuse, Normal,
1444        template!(List: &[r#"cfg = "...", module = "...", kind = "...""#]), DuplicatesOk,
1445        EncodeCrossCrate::No
1446    ),
1447    rustc_attr!(
1448        TEST, rustc_symbol_name, Normal, template!(Word),
1449        WarnFollowing, EncodeCrossCrate::No
1450    ),
1451    rustc_attr!(
1452        TEST, rustc_def_path, Normal, template!(Word),
1453        WarnFollowing, EncodeCrossCrate::No
1454    ),
1455    rustc_attr!(
1456        TEST, rustc_mir, Normal, template!(List: &["arg1, arg2, ..."]),
1457        DuplicatesOk, EncodeCrossCrate::Yes
1458    ),
1459    gated!(
1460        custom_mir, Normal, template!(List: &[r#"dialect = "...", phase = "...""#]),
1461        ErrorFollowing, EncodeCrossCrate::No,
1462        "the `#[custom_mir]` attribute is just used for the Rust test suite",
1463    ),
1464    rustc_attr!(
1465        TEST, rustc_dump_item_bounds, Normal, template!(Word),
1466        WarnFollowing, EncodeCrossCrate::No
1467    ),
1468    rustc_attr!(
1469        TEST, rustc_dump_predicates, Normal, template!(Word),
1470        WarnFollowing, EncodeCrossCrate::No
1471    ),
1472    rustc_attr!(
1473        TEST, rustc_dump_def_parents, Normal, template!(Word),
1474        WarnFollowing, EncodeCrossCrate::No
1475    ),
1476    rustc_attr!(
1477        TEST, rustc_object_lifetime_default, Normal, template!(Word),
1478        WarnFollowing, EncodeCrossCrate::No
1479    ),
1480    rustc_attr!(
1481        TEST, rustc_dump_vtable, Normal, template!(Word),
1482        WarnFollowing, EncodeCrossCrate::No
1483    ),
1484    rustc_attr!(
1485        TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/),
1486        DuplicatesOk, EncodeCrossCrate::No
1487    ),
1488    rustc_attr!(
1489        TEST, pattern_complexity_limit, CrateLevel, template!(NameValueStr: "N"),
1490        ErrorFollowing, EncodeCrossCrate::No,
1491    ),
1492];
1493
1494pub fn is_builtin_attr_name(name: Symbol) -> bool {
1495    BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
1496}
1497
1498/// Whether this builtin attribute is encoded cross crate.
1499/// This means it can be used cross crate.
1500pub fn encode_cross_crate(name: Symbol) -> bool {
1501    if let Some(attr) = BUILTIN_ATTRIBUTE_MAP.get(&name) {
1502        attr.encode_cross_crate == EncodeCrossCrate::Yes
1503    } else {
1504        true
1505    }
1506}
1507
1508pub fn is_valid_for_get_attr(name: Symbol) -> bool {
1509    BUILTIN_ATTRIBUTE_MAP.get(&name).is_some_and(|attr| match attr.duplicates {
1510        WarnFollowing | ErrorFollowing | ErrorPreceding | FutureWarnFollowing
1511        | FutureWarnPreceding => true,
1512        DuplicatesOk | WarnFollowingWordOnly => false,
1513    })
1514}
1515
1516pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>> =
1517    LazyLock::new(|| {
1518        let mut map = FxHashMap::default();
1519        for attr in BUILTIN_ATTRIBUTES.iter() {
1520            if map.insert(attr.name, attr).is_some() {
1521                panic!("duplicate builtin attribute `{}`", attr.name);
1522            }
1523        }
1524        map
1525    });
1526
1527pub fn is_stable_diagnostic_attribute(sym: Symbol, _features: &Features) -> bool {
1528    match sym {
1529        sym::on_unimplemented | sym::do_not_recommend => true,
1530        _ => false,
1531    }
1532}
rustc_feature/builtin_attrs.rs

rustc_feature/
builtin_attrs.rs
