1 //! Built-in attributes and `cfg` flag gating.
3 use AttributeDuplicates::*;
7 use crate::{Features, Stability};
9 use rustc_data_structures::fx::FxHashMap;
10 use rustc_span::symbol::{sym, Symbol};
12 use std::sync::LazyLock;
14 type GateFn = fn(&Features) -> bool;
18 (|features| features.$field) as GateFn
22 pub type GatedCfg = (Symbol, Symbol, GateFn);
24 /// `cfg(...)`'s that are feature gated.
25 const GATED_CFGS: &[GatedCfg] = &[
26 // (name in cfg, feature, function to check if the feature is enabled)
27 (sym::target_abi, sym::cfg_target_abi, cfg_fn!(cfg_target_abi)),
28 (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
30 sym::target_has_atomic_equal_alignment,
31 sym::cfg_target_has_atomic_equal_alignment,
32 cfg_fn!(cfg_target_has_atomic_equal_alignment),
34 (sym::target_has_atomic_load_store, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
35 (sym::sanitize, sym::cfg_sanitize, cfg_fn!(cfg_sanitize)),
36 (sym::version, sym::cfg_version, cfg_fn!(cfg_version)),
39 /// Find a gated cfg determined by the `pred`icate which is given the cfg's name.
40 pub fn find_gated_cfg(pred: impl Fn(Symbol) -> bool) -> Option<&'static GatedCfg> {
41 GATED_CFGS.iter().find(|(cfg_sym, ..)| pred(*cfg_sym))
44 // If you change this, please modify `src/doc/unstable-book` as well. You must
45 // move that documentation into the relevant place in the other docs, and
46 // remove the chapter on the flag.
48 #[derive(Copy, Clone, PartialEq, Debug)]
49 pub enum AttributeType {
50 /// Normal, builtin attribute that is consumed
51 /// by the compiler before the unused_attribute check
54 /// Builtin attribute that is only allowed at the crate level
58 #[derive(Clone, Copy)]
59 pub enum AttributeGate {
60 /// Is gated by a given feature gate, reason
61 /// and function to check if enabled
62 Gated(Stability, Symbol, &'static str, fn(&Features) -> bool),
64 /// Ungated attribute, can be used on all release channels
69 impl std::fmt::Debug for AttributeGate {
70 fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
72 Self::Gated(ref stab, name, expl, _) => {
73 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl)
75 Self::Ungated => write!(fmt, "Ungated"),
81 fn is_deprecated(&self) -> bool {
82 matches!(*self, Self::Gated(Stability::Deprecated(_, _), ..))
86 /// A template that the attribute input must match.
87 /// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
88 #[derive(Clone, Copy, Default)]
89 pub struct AttributeTemplate {
90 /// If `true`, the attribute is allowed to be a bare word like `#[test]`.
92 /// If `Some`, the attribute is allowed to take a list of items like `#[allow(..)]`.
93 pub list: Option<&'static str>,
94 /// If `Some`, the attribute is allowed to be a name/value pair where the
95 /// value is a string, like `#[must_use = "reason"]`.
96 pub name_value_str: Option<&'static str>,
99 /// How to handle multiple duplicate attributes on the same item.
100 #[derive(Clone, Copy, Default)]
101 pub enum AttributeDuplicates {
102 /// Duplicates of this attribute are allowed.
104 /// This should only be used with attributes where duplicates have semantic
105 /// meaning, or some kind of "additive" behavior. For example, `#[warn(..)]`
106 /// can be specified multiple times, and it combines all the entries. Or use
107 /// this if there is validation done elsewhere.
110 /// Duplicates after the first attribute will be an unused_attribute warning.
112 /// This is usually used for "word" attributes, where they are used as a
113 /// boolean marker, like `#[used]`. It is not necessarily wrong that there
114 /// are duplicates, but the others should probably be removed.
116 /// Same as `WarnFollowing`, but only issues warnings for word-style attributes.
118 /// This is only for special cases, for example multiple `#[macro_use]` can
119 /// be warned, but multiple `#[macro_use(...)]` should not because the list
120 /// form has different meaning from the word form.
121 WarnFollowingWordOnly,
122 /// Duplicates after the first attribute will be an error.
124 /// This should be used where duplicates would be ignored, but carry extra
125 /// meaning that could cause confusion. For example, `#[stable(since="1.0")]
126 /// #[stable(since="2.0")]`, which version should be used for `stable`?
128 /// Duplicates preceding the last instance of the attribute will be an error.
130 /// This is the same as `ErrorFollowing`, except the last attribute is the
131 /// one that is "used". This is typically used in cases like codegen
132 /// attributes which usually only honor the last attribute.
134 /// Duplicates after the first attribute will be an unused_attribute warning
135 /// with a note that this will be an error in the future.
137 /// This should be used for attributes that should be `ErrorFollowing`, but
138 /// because older versions of rustc silently accepted (and ignored) the
139 /// attributes, this is used to transition.
141 /// Duplicates preceding the last instance of the attribute will be a
142 /// warning, with a note that this will be an error in the future.
144 /// This is the same as `FutureWarnFollowing`, except the last attribute is
145 /// the one that is "used". Ideally these can eventually migrate to
146 /// `ErrorPreceding`.
150 /// A convenience macro to deal with `$($expr)?`.
151 macro_rules! or_default {
152 ($default:expr,) => {
155 ($default:expr, $next:expr) => {
160 /// A convenience macro for constructing attribute templates.
161 /// E.g., `template!(Word, List: "description")` means that the attribute
162 /// supports forms `#[attr]` and `#[attr(description)]`.
163 macro_rules! template {
164 (Word) => { template!(@ true, None, None) };
165 (List: $descr: expr) => { template!(@ false, Some($descr), None) };
166 (NameValueStr: $descr: expr) => { template!(@ false, None, Some($descr)) };
167 (Word, List: $descr: expr) => { template!(@ true, Some($descr), None) };
168 (Word, NameValueStr: $descr: expr) => { template!(@ true, None, Some($descr)) };
169 (List: $descr1: expr, NameValueStr: $descr2: expr) => {
170 template!(@ false, Some($descr1), Some($descr2))
172 (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
173 template!(@ true, Some($descr1), Some($descr2))
175 (@ $word: expr, $list: expr, $name_value_str: expr) => { AttributeTemplate {
176 word: $word, list: $list, name_value_str: $name_value_str
180 macro_rules! ungated {
181 ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr $(, @only_local: $only_local:expr)? $(,)?) => {
184 only_local: or_default!(false, $($only_local)?),
188 duplicates: $duplicates,
194 ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr $(, @only_local: $only_local:expr)?, $gate:ident, $msg:expr $(,)?) => {
197 only_local: or_default!(false, $($only_local)?),
200 duplicates: $duplicates,
201 gate: Gated(Stability::Unstable, sym::$gate, $msg, cfg_fn!($gate)),
204 ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr $(, @only_local: $only_local:expr)?, $msg:expr $(,)?) => {
207 only_local: or_default!(false, $($only_local)?),
210 duplicates: $duplicates,
211 gate: Gated(Stability::Unstable, sym::$attr, $msg, cfg_fn!($attr)),
216 macro_rules! rustc_attr {
217 (TEST, $attr:ident, $typ:expr, $tpl:expr, $duplicate:expr $(, @only_local: $only_local:expr)? $(,)?) => {
223 $(@only_local: $only_local,)?
227 "]` attribute is just used for rustc unit tests \
228 and will never be stable",
232 ($attr:ident, $typ:expr, $tpl:expr, $duplicates:expr $(, @only_local: $only_local:expr)?, $msg:expr $(,)?) => {
235 only_local: or_default!(false, $($only_local)?),
238 duplicates: $duplicates,
239 gate: Gated(Stability::Unstable, sym::rustc_attrs, $msg, cfg_fn!(rustc_attrs)),
244 macro_rules! experimental {
246 concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
250 const IMPL_DETAIL: &str = "internal implementation detail";
251 const INTERNAL_UNSTABLE: &str = "this is an internal attribute that will never be stable";
253 pub struct BuiltinAttribute {
255 /// Whether this attribute is only used in the local crate.
257 /// If so, it is not encoded in the crate metadata.
258 pub only_local: bool,
259 pub type_: AttributeType,
260 pub template: AttributeTemplate,
261 pub duplicates: AttributeDuplicates,
262 pub gate: AttributeGate,
265 /// Attributes that have a special meaning to rustc or rustdoc.
267 pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
268 // ==========================================================================
269 // Stable attributes:
270 // ==========================================================================
272 // Conditional compilation:
273 ungated!(cfg, Normal, template!(List: "predicate"), DuplicatesOk),
274 ungated!(cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ..."), DuplicatesOk),
277 ungated!(ignore, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing),
279 should_panic, Normal,
280 template!(Word, List: r#"expected = "reason""#, NameValueStr: "reason"), FutureWarnFollowing,
282 // FIXME(Centril): This can be used on stable but shouldn't.
283 ungated!(reexport_test_harness_main, CrateLevel, template!(NameValueStr: "name"), ErrorFollowing),
286 ungated!(automatically_derived, Normal, template!(Word), WarnFollowing),
287 ungated!(macro_use, Normal, template!(Word, List: "name1, name2, ..."), WarnFollowingWordOnly),
288 ungated!(macro_escape, Normal, template!(Word), WarnFollowing), // Deprecated synonym for `macro_use`.
289 ungated!(macro_export, Normal, template!(Word, List: "local_inner_macros"), WarnFollowing),
290 ungated!(proc_macro, Normal, template!(Word), ErrorFollowing),
292 proc_macro_derive, Normal,
293 template!(List: "TraitName, /*opt*/ attributes(name1, name2, ...)"), ErrorFollowing,
295 ungated!(proc_macro_attribute, Normal, template!(Word), ErrorFollowing),
299 warn, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
300 DuplicatesOk, @only_local: true,
303 allow, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
304 DuplicatesOk, @only_local: true,
307 expect, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#), DuplicatesOk,
308 lint_reasons, experimental!(expect)
311 forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
312 DuplicatesOk, @only_local: true,
315 deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#),
316 DuplicatesOk, @only_local: true,
318 ungated!(must_use, Normal, template!(Word, NameValueStr: "reason"), FutureWarnFollowing),
320 must_not_suspend, Normal, template!(Word, NameValueStr: "reason"), WarnFollowing,
321 experimental!(must_not_suspend)
327 List: r#"/*opt*/ since = "version", /*opt*/ note = "reason""#,
328 NameValueStr: "reason"
334 ungated!(crate_name, CrateLevel, template!(NameValueStr: "name"), FutureWarnFollowing),
335 ungated!(crate_type, CrateLevel, template!(NameValueStr: "bin|lib|..."), DuplicatesOk),
336 // crate_id is deprecated
337 ungated!(crate_id, CrateLevel, template!(NameValueStr: "ignored"), FutureWarnFollowing),
339 // ABI, linking, symbols, and FFI
342 template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...", /*opt*/ wasm_import_module = "...", /*opt*/ import_name_type = "decorated|noprefix|undecorated""#),
345 ungated!(link_name, Normal, template!(NameValueStr: "name"), FutureWarnPreceding),
346 ungated!(no_link, Normal, template!(Word), WarnFollowing),
347 ungated!(repr, Normal, template!(List: "C"), DuplicatesOk, @only_local: true),
348 ungated!(export_name, Normal, template!(NameValueStr: "name"), FutureWarnPreceding),
349 ungated!(link_section, Normal, template!(NameValueStr: "name"), FutureWarnPreceding),
350 ungated!(no_mangle, Normal, template!(Word), WarnFollowing, @only_local: true),
351 ungated!(used, Normal, template!(Word, List: "compiler|linker"), WarnFollowing, @only_local: true),
352 ungated!(link_ordinal, Normal, template!(List: "ordinal"), ErrorPreceding),
355 ungated!(recursion_limit, CrateLevel, template!(NameValueStr: "N"), FutureWarnFollowing),
356 ungated!(type_length_limit, CrateLevel, template!(NameValueStr: "N"), FutureWarnFollowing),
358 const_eval_limit, CrateLevel, template!(NameValueStr: "N"), ErrorFollowing,
359 const_eval_limit, experimental!(const_eval_limit)
362 move_size_limit, CrateLevel, template!(NameValueStr: "N"), ErrorFollowing,
363 large_assignments, experimental!(move_size_limit)
367 gated!(unix_sigpipe, Normal, template!(Word, NameValueStr: "inherit|sig_ign|sig_dfl"), ErrorFollowing, experimental!(unix_sigpipe)),
368 ungated!(start, Normal, template!(Word), WarnFollowing),
369 ungated!(no_start, CrateLevel, template!(Word), WarnFollowing),
370 ungated!(no_main, CrateLevel, template!(Word), WarnFollowing),
372 // Modules, prelude, and resolution:
373 ungated!(path, Normal, template!(NameValueStr: "file"), FutureWarnFollowing),
374 ungated!(no_std, CrateLevel, template!(Word), WarnFollowing),
375 ungated!(no_implicit_prelude, Normal, template!(Word), WarnFollowing),
376 ungated!(non_exhaustive, Normal, template!(Word), WarnFollowing),
380 windows_subsystem, CrateLevel,
381 template!(NameValueStr: "windows|console"), FutureWarnFollowing
383 ungated!(panic_handler, Normal, template!(Word), WarnFollowing), // RFC 2070
386 ungated!(inline, Normal, template!(Word, List: "always|never"), FutureWarnFollowing, @only_local: true),
387 ungated!(cold, Normal, template!(Word), WarnFollowing, @only_local: true),
388 ungated!(no_builtins, CrateLevel, template!(Word), WarnFollowing),
390 target_feature, Normal, template!(List: r#"enable = "name""#),
391 DuplicatesOk, @only_local: true,
393 ungated!(track_caller, Normal, template!(Word), WarnFollowing),
394 ungated!(instruction_set, Normal, template!(List: "set"), ErrorPreceding),
397 template!(List: "address, memory, thread"), DuplicatesOk,
398 experimental!(no_sanitize)
400 gated!(no_coverage, Normal, template!(Word), WarnFollowing, experimental!(no_coverage)),
403 doc, Normal, template!(List: "hidden|inline|...", NameValueStr: "string"), DuplicatesOk
406 // ==========================================================================
407 // Unstable attributes:
408 // ==========================================================================
410 // RFC #3191: #[debugger_visualizer] support
412 debugger_visualizer, Normal, template!(List: r#"natvis_file = "...", gdb_script_file = "...""#),
413 DuplicatesOk, experimental!(debugger_visualizer)
417 gated!(naked, Normal, template!(Word), WarnFollowing, @only_local: true, naked_functions, experimental!(naked)),
424 template: template!(List: "name"),
425 duplicates: DuplicatesOk,
427 Stability::Deprecated(
428 "https://github.com/rust-lang/rust/pull/64675",
429 Some("may be removed in a future compiler version"),
432 "compiler plugins are deprecated",
439 test_runner, CrateLevel, template!(List: "path"), ErrorFollowing, custom_test_frameworks,
440 "custom test frameworks are an unstable feature",
444 marker, Normal, template!(Word), WarnFollowing, marker_trait_attr, experimental!(marker)
447 thread_local, Normal, template!(Word), WarnFollowing,
448 "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
450 gated!(no_core, CrateLevel, template!(Word), WarnFollowing, experimental!(no_core)),
453 optimize, Normal, template!(List: "size|speed"), ErrorPreceding, optimize_attribute,
454 experimental!(optimize),
458 ffi_returns_twice, Normal, template!(Word), WarnFollowing, experimental!(ffi_returns_twice)
460 gated!(ffi_pure, Normal, template!(Word), WarnFollowing, experimental!(ffi_pure)),
461 gated!(ffi_const, Normal, template!(Word), WarnFollowing, experimental!(ffi_const)),
463 register_tool, CrateLevel, template!(List: "tool1, tool2, ..."), DuplicatesOk,
464 experimental!(register_tool),
468 cmse_nonsecure_entry, Normal, template!(Word), WarnFollowing,
469 experimental!(cmse_nonsecure_entry)
473 const_trait, Normal, template!(Word), WarnFollowing, const_trait_impl,
474 "`const_trait` is a temporary placeholder for marking a trait that is suitable for `const` \
475 `impls` and all default bodies as `const`, which may be removed or renamed in the \
480 deprecated_safe, Normal, template!(List: r#"since = "version", note = "...""#), ErrorFollowing,
481 experimental!(deprecated_safe),
484 // `#[collapse_debuginfo]`
486 collapse_debuginfo, Normal, template!(Word), WarnFollowing,
487 experimental!(collapse_debuginfo)
490 // ==========================================================================
491 // Internal attributes: Stability, deprecation, and unsafe:
492 // ==========================================================================
496 template!(List: "name1, name2, ..."), DuplicatesOk, @only_local: true,
498 // DuplicatesOk since it has its own validation
501 template!(List: r#"feature = "name", since = "version""#), DuplicatesOk, @only_local: true,
505 template!(List: r#"feature = "name", reason = "...", issue = "N""#), DuplicatesOk,
507 ungated!(rustc_const_unstable, Normal, template!(List: r#"feature = "name""#), DuplicatesOk),
509 rustc_const_stable, Normal,
510 template!(List: r#"feature = "name""#), DuplicatesOk, @only_local: true,
513 rustc_default_body_unstable, Normal,
514 template!(List: r#"feature = "name", reason = "...", issue = "N""#), DuplicatesOk
517 allow_internal_unstable, Normal, template!(Word, List: "feat1, feat2, ..."), DuplicatesOk,
518 "allow_internal_unstable side-steps feature gating and stability checks",
521 rustc_allow_const_fn_unstable, Normal,
522 template!(Word, List: "feat1, feat2, ..."), DuplicatesOk,
523 "rustc_allow_const_fn_unstable side-steps feature gating and stability checks"
526 allow_internal_unsafe, Normal, template!(Word), WarnFollowing,
527 "allow_internal_unsafe side-steps the unsafe_code lint",
529 ungated!(rustc_safe_intrinsic, Normal, template!(Word), DuplicatesOk),
530 rustc_attr!(rustc_allowed_through_unstable_modules, Normal, template!(Word), WarnFollowing,
531 "rustc_allowed_through_unstable_modules special cases accidental stabilizations of stable items \
532 through unstable paths"),
534 // ==========================================================================
535 // Internal attributes: Type system related:
536 // ==========================================================================
538 gated!(fundamental, Normal, template!(Word), WarnFollowing, experimental!(fundamental)),
540 may_dangle, Normal, template!(Word), WarnFollowing, dropck_eyepatch,
541 "`may_dangle` has unstable semantics and may be removed in the future",
544 // ==========================================================================
545 // Internal attributes: Runtime related:
546 // ==========================================================================
548 rustc_attr!(rustc_allocator, Normal, template!(Word), WarnFollowing, IMPL_DETAIL),
549 rustc_attr!(rustc_nounwind, Normal, template!(Word), WarnFollowing, IMPL_DETAIL),
550 rustc_attr!(rustc_reallocator, Normal, template!(Word), WarnFollowing, IMPL_DETAIL),
551 rustc_attr!(rustc_deallocator, Normal, template!(Word), WarnFollowing, IMPL_DETAIL),
552 rustc_attr!(rustc_allocator_zeroed, Normal, template!(Word), WarnFollowing, IMPL_DETAIL),
554 default_lib_allocator, Normal, template!(Word), WarnFollowing, allocator_internals,
555 experimental!(default_lib_allocator),
558 needs_allocator, Normal, template!(Word), WarnFollowing, allocator_internals,
559 experimental!(needs_allocator),
561 gated!(panic_runtime, Normal, template!(Word), WarnFollowing, experimental!(panic_runtime)),
563 needs_panic_runtime, Normal, template!(Word), WarnFollowing,
564 experimental!(needs_panic_runtime)
567 compiler_builtins, Normal, template!(Word), WarnFollowing,
568 "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
569 which contains compiler-rt intrinsics and will never be stable",
572 profiler_runtime, Normal, template!(Word), WarnFollowing,
573 "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
574 which contains the profiler runtime and will never be stable",
577 // ==========================================================================
578 // Internal attributes, Linkage:
579 // ==========================================================================
582 linkage, Normal, template!(NameValueStr: "external|internal|..."), ErrorPreceding, @only_local: true,
583 "the `linkage` attribute is experimental and not portable across platforms",
586 rustc_std_internal_symbol, Normal, template!(Word), WarnFollowing, @only_local: true, INTERNAL_UNSTABLE
589 // ==========================================================================
590 // Internal attributes, Macro related:
591 // ==========================================================================
594 rustc_builtin_macro, Normal,
595 template!(Word, List: "name, /*opt*/ attributes(name1, name2, ...)"), ErrorFollowing,
598 rustc_attr!(rustc_proc_macro_decls, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE),
600 rustc_macro_transparency, Normal,
601 template!(NameValueStr: "transparent|semitransparent|opaque"), ErrorFollowing,
602 "used internally for testing macro hygiene",
605 // ==========================================================================
606 // Internal attributes, Diagnostics related:
607 // ==========================================================================
610 rustc_on_unimplemented, Normal,
612 List: r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
613 NameValueStr: "message"
618 // Enumerates "identity-like" conversion methods to suggest on type mismatch.
620 rustc_conversion_suggestion, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE
622 // Prevents field reads in the marked trait or method to be considered
623 // during dead code analysis.
625 rustc_trivial_field_reads, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE
627 // Used by the `rustc::potential_query_instability` lint to warn methods which
628 // might not be stable during incremental compilation.
629 rustc_attr!(rustc_lint_query_instability, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE),
630 // Used by the `rustc::untranslatable_diagnostic` and `rustc::diagnostic_outside_of_impl` lints
631 // to assist in changes to diagnostic APIs.
632 rustc_attr!(rustc_lint_diagnostics, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE),
633 // Used by the `rustc::bad_opt_access` lint to identify `DebuggingOptions` and `CodegenOptions`
634 // types (as well as any others in future).
635 rustc_attr!(rustc_lint_opt_ty, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE),
636 // Used by the `rustc::bad_opt_access` lint on fields
637 // types (as well as any others in future).
638 rustc_attr!(rustc_lint_opt_deny_field_access, Normal, template!(List: "message"), WarnFollowing, INTERNAL_UNSTABLE),
640 // ==========================================================================
641 // Internal attributes, Const related:
642 // ==========================================================================
644 rustc_attr!(rustc_promotable, Normal, template!(Word), WarnFollowing, IMPL_DETAIL),
646 rustc_legacy_const_generics, Normal, template!(List: "N"), ErrorFollowing,
649 // Do not const-check this function's body. It will always get replaced during CTFE.
651 rustc_do_not_const_check, Normal, template!(Word), WarnFollowing, INTERNAL_UNSTABLE
654 // ==========================================================================
655 // Internal attributes, Layout related:
656 // ==========================================================================
659 rustc_layout_scalar_valid_range_start, Normal, template!(List: "value"), ErrorFollowing,
660 "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
661 niche optimizations in libcore and libstd and will never be stable",
664 rustc_layout_scalar_valid_range_end, Normal, template!(List: "value"), ErrorFollowing,
665 "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
666 niche optimizations in libcore and libstd and will never be stable",
669 rustc_nonnull_optimization_guaranteed, Normal, template!(Word), WarnFollowing,
670 "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
671 niche optimizations in libcore and libstd and will never be stable",
674 // ==========================================================================
675 // Internal attributes, Misc:
676 // ==========================================================================
678 lang, Normal, template!(NameValueStr: "name"), DuplicatesOk, @only_local: true, lang_items,
679 "language items are subject to change",
682 rustc_pass_by_value, Normal,
683 template!(Word), ErrorFollowing,
684 "#[rustc_pass_by_value] is used to mark types that must be passed by value instead of reference."
687 rustc_coherence_is_core, AttributeType::CrateLevel, template!(Word), ErrorFollowing, @only_local: true,
688 "#![rustc_coherence_is_core] allows inherent methods on builtin types, only intended to be used in `core`."
691 rustc_allow_incoherent_impl, AttributeType::Normal, template!(Word), ErrorFollowing, @only_local: true,
692 "#[rustc_allow_incoherent_impl] has to be added to all impl items of an incoherent inherent impl."
695 rustc_deny_explicit_impl, AttributeType::Normal, template!(Word), ErrorFollowing, @only_local: false,
696 "#[rustc_deny_explicit_impl] enforces that a trait can have no user-provided impls"
699 rustc_has_incoherent_inherent_impls, AttributeType::Normal, template!(Word), ErrorFollowing,
700 "#[rustc_has_incoherent_inherent_impls] allows the addition of incoherent inherent impls for \
701 the given type by annotating all impl items with #[rustc_allow_incoherent_impl]."
704 rustc_box, AttributeType::Normal, template!(Word), ErrorFollowing,
705 "#[rustc_box] allows creating boxes \
706 and it is only intended to be used in `alloc`."
710 name: sym::rustc_diagnostic_item,
711 // FIXME: This can be `true` once we always use `tcx.is_diagnostic_item`.
714 template: template!(NameValueStr: "name"),
715 duplicates: ErrorFollowing,
719 "diagnostic items compiler internal support for linting",
720 cfg_fn!(rustc_attrs),
725 prelude_import, Normal, template!(Word), WarnFollowing,
726 "`#[prelude_import]` is for use by rustc only",
729 rustc_paren_sugar, Normal, template!(Word), WarnFollowing, unboxed_closures,
730 "unboxed_closures are still evolving",
733 rustc_inherit_overflow_checks, Normal, template!(Word), WarnFollowing, @only_local: true,
734 "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
735 overflow checking behavior of several libcore functions that are inlined \
736 across crates and will never be stable",
739 rustc_reservation_impl, Normal,
740 template!(NameValueStr: "reservation message"), ErrorFollowing,
741 "the `#[rustc_reservation_impl]` attribute is internally used \
742 for reserving for `for<T> From<!> for T` impl"
745 rustc_test_marker, Normal, template!(NameValueStr: "name"), WarnFollowing,
746 "the `#[rustc_test_marker]` attribute is used internally to track tests",
749 rustc_unsafe_specialization_marker, Normal, template!(Word), WarnFollowing,
750 "the `#[rustc_unsafe_specialization_marker]` attribute is used to check specializations"
753 rustc_specialization_trait, Normal, template!(Word), WarnFollowing,
754 "the `#[rustc_specialization_trait]` attribute is used to check specializations"
757 rustc_main, Normal, template!(Word), WarnFollowing,
758 "the `#[rustc_main]` attribute is used internally to specify test entry point function",
761 rustc_skip_array_during_method_dispatch, Normal, template!(Word), WarnFollowing,
762 "the `#[rustc_skip_array_during_method_dispatch]` attribute is used to exclude a trait \
763 from method dispatch when the receiver is an array, for compatibility in editions < 2021."
766 rustc_must_implement_one_of, Normal, template!(List: "function1, function2, ..."), ErrorFollowing,
767 "the `#[rustc_must_implement_one_of]` attribute is used to change minimal complete \
768 definition of a trait, it's currently in experimental form and should be changed before \
769 being exposed outside of the std"
772 // ==========================================================================
773 // Internal attributes, Testing:
774 // ==========================================================================
776 rustc_attr!(TEST, rustc_effective_visibility, Normal, template!(Word), WarnFollowing),
777 rustc_attr!(TEST, rustc_outlives, Normal, template!(Word), WarnFollowing),
778 rustc_attr!(TEST, rustc_capture_analysis, Normal, template!(Word), WarnFollowing),
779 rustc_attr!(TEST, rustc_insignificant_dtor, Normal, template!(Word), WarnFollowing),
780 rustc_attr!(TEST, rustc_strict_coherence, Normal, template!(Word), WarnFollowing),
781 rustc_attr!(TEST, rustc_variance, Normal, template!(Word), WarnFollowing),
782 rustc_attr!(TEST, rustc_layout, Normal, template!(List: "field1, field2, ..."), WarnFollowing),
783 rustc_attr!(TEST, rustc_regions, Normal, template!(Word), WarnFollowing),
785 TEST, rustc_error, Normal,
786 template!(Word, List: "delay_span_bug_from_inside_query"), WarnFollowingWordOnly
788 rustc_attr!(TEST, rustc_dump_user_substs, Normal, template!(Word), WarnFollowing),
789 rustc_attr!(TEST, rustc_evaluate_where_clauses, Normal, template!(Word), WarnFollowing),
791 TEST, rustc_if_this_changed, Normal, template!(Word, List: "DepNode"), DuplicatesOk
794 TEST, rustc_then_this_would_need, Normal, template!(List: "DepNode"), DuplicatesOk
797 TEST, rustc_clean, Normal,
798 template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
802 TEST, rustc_partition_reused, Normal,
803 template!(List: r#"cfg = "...", module = "...""#), DuplicatesOk,
806 TEST, rustc_partition_codegened, Normal,
807 template!(List: r#"cfg = "...", module = "...""#), DuplicatesOk,
810 TEST, rustc_expected_cgu_reuse, Normal,
811 template!(List: r#"cfg = "...", module = "...", kind = "...""#), DuplicatesOk,
813 rustc_attr!(TEST, rustc_symbol_name, Normal, template!(Word), WarnFollowing),
814 rustc_attr!(TEST, rustc_polymorphize_error, Normal, template!(Word), WarnFollowing),
815 rustc_attr!(TEST, rustc_def_path, Normal, template!(Word), WarnFollowing),
816 rustc_attr!(TEST, rustc_mir, Normal, template!(List: "arg1, arg2, ..."), DuplicatesOk),
818 custom_mir, Normal, template!(List: r#"dialect = "...", phase = "...""#),
819 ErrorFollowing, "the `#[custom_mir]` attribute is just used for the Rust test suite",
821 rustc_attr!(TEST, rustc_dump_program_clauses, Normal, template!(Word), WarnFollowing),
822 rustc_attr!(TEST, rustc_dump_env_program_clauses, Normal, template!(Word), WarnFollowing),
823 rustc_attr!(TEST, rustc_object_lifetime_default, Normal, template!(Word), WarnFollowing),
824 rustc_attr!(TEST, rustc_dump_vtable, Normal, template!(Word), WarnFollowing),
825 rustc_attr!(TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/), DuplicatesOk),
827 omit_gdb_pretty_printer_section, Normal, template!(Word), WarnFollowing,
828 "the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
832 pub fn deprecated_attributes() -> Vec<&'static BuiltinAttribute> {
833 BUILTIN_ATTRIBUTES.iter().filter(|attr| attr.gate.is_deprecated()).collect()
836 pub fn is_builtin_attr_name(name: Symbol) -> bool {
837 BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
840 /// Whether this builtin attribute is only used in the local crate.
841 /// If so, it is not encoded in the crate metadata.
842 pub fn is_builtin_only_local(name: Symbol) -> bool {
843 BUILTIN_ATTRIBUTE_MAP.get(&name).map_or(false, |attr| attr.only_local)
846 pub fn is_valid_for_get_attr(name: Symbol) -> bool {
847 BUILTIN_ATTRIBUTE_MAP.get(&name).map_or(false, |attr| match attr.duplicates {
848 WarnFollowing | ErrorFollowing | ErrorPreceding | FutureWarnFollowing
849 | FutureWarnPreceding => true,
850 DuplicatesOk | WarnFollowingWordOnly => false,
854 pub static BUILTIN_ATTRIBUTE_MAP: LazyLock<FxHashMap<Symbol, &BuiltinAttribute>> =
856 let mut map = FxHashMap::default();
857 for attr in BUILTIN_ATTRIBUTES.iter() {
858 if map.insert(attr.name, attr).is_some() {
859 panic!("duplicate builtin attribute `{}`", attr.name);