1 //! Built-in attributes and `cfg` flag gating.
6 use crate::{Features, Stability};
8 use lazy_static::lazy_static;
9 use rustc_data_structures::fx::FxHashMap;
10 use rustc_span::symbol::{sym, Symbol};
12 type GateFn = fn(&Features) -> bool;
16 (|features| features.$field) as GateFn
20 pub type GatedCfg = (Symbol, Symbol, GateFn);
22 /// `cfg(...)`'s that are feature gated.
23 const GATED_CFGS: &[GatedCfg] = &[
24 // (name in cfg, feature, function to check if the feature is enabled)
25 (sym::target_thread_local, sym::cfg_target_thread_local, cfg_fn!(cfg_target_thread_local)),
26 (sym::target_has_atomic, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
27 (sym::target_has_atomic_load_store, sym::cfg_target_has_atomic, cfg_fn!(cfg_target_has_atomic)),
28 (sym::sanitize, sym::cfg_sanitize, cfg_fn!(cfg_sanitize)),
31 /// Find a gated cfg determined by the `pred`icate which is given the cfg's name.
32 pub fn find_gated_cfg(pred: impl Fn(Symbol) -> bool) -> Option<&'static GatedCfg> {
33 GATED_CFGS.iter().find(|(cfg_sym, ..)| pred(*cfg_sym))
36 // If you change this, please modify `src/doc/unstable-book` as well. You must
37 // move that documentation into the relevant place in the other docs, and
38 // remove the chapter on the flag.
40 #[derive(Copy, Clone, PartialEq, Debug)]
41 pub enum AttributeType {
42 /// Normal, builtin attribute that is consumed
43 /// by the compiler before the unused_attribute check
46 /// Builtin attribute that may not be consumed by the compiler
47 /// before the unused_attribute check. These attributes
48 /// will be ignored by the unused_attribute lint
51 /// Builtin attribute that is only allowed at the crate level
55 #[derive(Clone, Copy)]
56 pub enum AttributeGate {
57 /// Is gated by a given feature gate, reason
58 /// and function to check if enabled
59 Gated(Stability, Symbol, &'static str, fn(&Features) -> bool),
61 /// Ungated attribute, can be used on all release channels
66 impl std::fmt::Debug for AttributeGate {
67 fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
69 Self::Gated(ref stab, name, expl, _) => {
70 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl)
72 Self::Ungated => write!(fmt, "Ungated"),
78 fn is_deprecated(&self) -> bool {
80 Self::Gated(Stability::Deprecated(_, _), ..) => true,
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)]
89 pub struct AttributeTemplate {
91 pub list: Option<&'static str>,
92 pub name_value_str: Option<&'static str>,
95 impl AttributeTemplate {
96 pub fn only_word() -> Self {
97 Self { word: true, list: None, name_value_str: None }
101 /// A convenience macro for constructing attribute templates.
102 /// E.g., `template!(Word, List: "description")` means that the attribute
103 /// supports forms `#[attr]` and `#[attr(description)]`.
104 macro_rules! template {
105 (Word) => { template!(@ true, None, None) };
106 (List: $descr: expr) => { template!(@ false, Some($descr), None) };
107 (NameValueStr: $descr: expr) => { template!(@ false, None, Some($descr)) };
108 (Word, List: $descr: expr) => { template!(@ true, Some($descr), None) };
109 (Word, NameValueStr: $descr: expr) => { template!(@ true, None, Some($descr)) };
110 (List: $descr1: expr, NameValueStr: $descr2: expr) => {
111 template!(@ false, Some($descr1), Some($descr2))
113 (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
114 template!(@ true, Some($descr1), Some($descr2))
116 (@ $word: expr, $list: expr, $name_value_str: expr) => { AttributeTemplate {
117 word: $word, list: $list, name_value_str: $name_value_str
121 macro_rules! ungated {
122 ($attr:ident, $typ:expr, $tpl:expr $(,)?) => {
123 (sym::$attr, $typ, $tpl, Ungated)
128 ($attr:ident, $typ:expr, $tpl:expr, $gate:ident, $msg:expr $(,)?) => {
129 (sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$gate, $msg, cfg_fn!($gate)))
131 ($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
132 (sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$attr, $msg, cfg_fn!($attr)))
136 macro_rules! rustc_attr {
137 (TEST, $attr:ident, $typ:expr, $tpl:expr $(,)?) => {
145 "]` attribute is just used for rustc unit tests \
146 and will never be stable",
150 ($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
155 Gated(Stability::Unstable, sym::rustc_attrs, $msg, cfg_fn!(rustc_attrs)),
160 macro_rules! experimental {
162 concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
166 const IMPL_DETAIL: &str = "internal implementation detail";
167 const INTERNAL_UNSTABLE: &str = "this is an internal attribute that will never be stable";
169 pub type BuiltinAttribute = (Symbol, AttributeType, AttributeTemplate, AttributeGate);
171 /// Attributes that have a special meaning to rustc or rustdoc.
173 pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
174 // ==========================================================================
175 // Stable attributes:
176 // ==========================================================================
178 // Condtional compilation:
179 ungated!(cfg, Normal, template!(List: "predicate")),
180 ungated!(cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ...")),
183 ungated!(ignore, Normal, template!(Word, NameValueStr: "reason")),
185 should_panic, Normal,
186 template!(Word, List: r#"expected = "reason"#, NameValueStr: "reason"),
188 // FIXME(Centril): This can be used on stable but shouldn't.
189 ungated!(reexport_test_harness_main, Normal, template!(NameValueStr: "name")),
192 ungated!(derive, Normal, template!(List: "Trait1, Trait2, ...")),
193 ungated!(automatically_derived, Normal, template!(Word)),
195 ungated!(macro_use, Normal, template!(Word, List: "name1, name2, ...")),
196 ungated!(macro_escape, Normal, template!(Word)), // Deprecated synonym for `macro_use`.
197 ungated!(macro_export, Normal, template!(Word, List: "local_inner_macros")),
198 ungated!(proc_macro, Normal, template!(Word)),
200 proc_macro_derive, Normal,
201 template!(List: "TraitName, /*opt*/ attributes(name1, name2, ...)"),
203 ungated!(proc_macro_attribute, Normal, template!(Word)),
206 ungated!(warn, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
207 ungated!(allow, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
208 ungated!(forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
209 ungated!(deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
210 ungated!(must_use, Whitelisted, template!(Word, NameValueStr: "reason")),
216 List: r#"/*opt*/ since = "version", /*opt*/ note = "reason""#,
217 NameValueStr: "reason"
222 ungated!(crate_name, CrateLevel, template!(NameValueStr: "name")),
223 ungated!(crate_type, CrateLevel, template!(NameValueStr: "bin|lib|...")),
224 ungated!(crate_id, CrateLevel, template!(NameValueStr: "ignored")),
226 // ABI, linking, symbols, and FFI
229 template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...", /*opt*/ cfg = "...""#),
231 ungated!(link_name, Whitelisted, template!(NameValueStr: "name")),
232 ungated!(no_link, Normal, template!(Word)),
233 ungated!(repr, Normal, template!(List: "C")),
234 ungated!(export_name, Whitelisted, template!(NameValueStr: "name")),
235 ungated!(link_section, Whitelisted, template!(NameValueStr: "name")),
236 ungated!(no_mangle, Whitelisted, template!(Word)),
237 ungated!(used, Whitelisted, template!(Word)),
240 ungated!(recursion_limit, CrateLevel, template!(NameValueStr: "N")),
241 ungated!(type_length_limit, CrateLevel, template!(NameValueStr: "N")),
243 const_eval_limit, CrateLevel, template!(NameValueStr: "N"), const_eval_limit,
244 experimental!(const_eval_limit)
248 ungated!(main, Normal, template!(Word)),
249 ungated!(start, Normal, template!(Word)),
250 ungated!(no_start, CrateLevel, template!(Word)),
251 ungated!(no_main, CrateLevel, template!(Word)),
253 // Modules, prelude, and resolution:
254 ungated!(path, Normal, template!(NameValueStr: "file")),
255 ungated!(no_std, CrateLevel, template!(Word)),
256 ungated!(no_implicit_prelude, Normal, template!(Word)),
257 ungated!(non_exhaustive, Whitelisted, template!(Word)),
260 ungated!(windows_subsystem, Whitelisted, template!(NameValueStr: "windows|console")),
261 ungated!(panic_handler, Normal, template!(Word)), // RFC 2070
264 ungated!(inline, Whitelisted, template!(Word, List: "always|never")),
265 ungated!(cold, Whitelisted, template!(Word)),
266 ungated!(no_builtins, Whitelisted, template!(Word)),
267 ungated!(target_feature, Whitelisted, template!(List: r#"enable = "name""#)),
269 no_sanitize, Whitelisted,
270 template!(List: "address, memory, thread"),
271 experimental!(no_sanitize)
274 // FIXME: #14408 whitelist docs since rustdoc looks at them
275 ungated!(doc, Whitelisted, template!(List: "hidden|inline|...", NameValueStr: "string")),
277 // ==========================================================================
278 // Unstable attributes:
279 // ==========================================================================
282 gated!(naked, Whitelisted, template!(Word), naked_functions, experimental!(naked)),
284 link_args, Normal, template!(NameValueStr: "args"),
285 "the `link_args` attribute is experimental and not portable across platforms, \
286 it is recommended to use `#[link(name = \"foo\")] instead",
289 link_ordinal, Whitelisted, template!(List: "ordinal"), raw_dylib,
290 experimental!(link_ordinal)
295 sym::plugin_registrar, Normal, template!(Word),
297 Stability::Deprecated(
298 "https://github.com/rust-lang/rust/pull/64675",
299 Some("may be removed in a future compiler version"),
301 sym::plugin_registrar,
302 "compiler plugins are deprecated",
303 cfg_fn!(plugin_registrar)
307 sym::plugin, CrateLevel, template!(List: "name"),
309 Stability::Deprecated(
310 "https://github.com/rust-lang/rust/pull/64675",
311 Some("may be removed in a future compiler version"),
314 "compiler plugins are deprecated",
320 gated!(allow_fail, Normal, template!(Word), experimental!(allow_fail)),
322 test_runner, CrateLevel, template!(List: "path"), custom_test_frameworks,
323 "custom test frameworks are an unstable feature",
326 gated!(marker, Normal, template!(Word), marker_trait_attr, experimental!(marker)),
328 thread_local, Whitelisted, template!(Word),
329 "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
331 gated!(no_core, CrateLevel, template!(Word), experimental!(no_core)),
334 optimize, Whitelisted, template!(List: "size|speed"), optimize_attribute,
335 experimental!(optimize),
338 gated!(ffi_returns_twice, Whitelisted, template!(Word), experimental!(ffi_returns_twice)),
339 gated!(track_caller, Whitelisted, template!(Word), experimental!(track_caller)),
341 register_attr, CrateLevel, template!(List: "attr1, attr2, ..."),
342 experimental!(register_attr),
345 register_tool, CrateLevel, template!(List: "tool1, tool2, ..."),
346 experimental!(register_tool),
349 // ==========================================================================
350 // Internal attributes: Stability, deprecation, and unsafe:
351 // ==========================================================================
353 ungated!(feature, CrateLevel, template!(List: "name1, name1, ...")),
354 // FIXME(#14407) -- only looked at on-demand so we can't
355 // guarantee they'll have already been checked.
357 rustc_deprecated, Whitelisted,
358 template!(List: r#"since = "version", reason = "...""#)
361 ungated!(stable, Whitelisted, template!(List: r#"feature = "name", since = "version""#)),
364 unstable, Whitelisted,
365 template!(List: r#"feature = "name", reason = "...", issue = "N""#),
368 ungated!(rustc_const_unstable, Whitelisted, template!(List: r#"feature = "name""#)),
370 ungated!(rustc_const_stable, Whitelisted, template!(List: r#"feature = "name""#)),
372 allow_internal_unstable, Normal, template!(Word, List: "feat1, feat2, ..."),
373 "allow_internal_unstable side-steps feature gating and stability checks",
376 allow_internal_unsafe, Normal, template!(Word),
377 "allow_internal_unsafe side-steps the unsafe_code lint",
380 // ==========================================================================
381 // Internal attributes: Type system related:
382 // ==========================================================================
384 gated!(fundamental, Whitelisted, template!(Word), experimental!(fundamental)),
387 structural_match, Whitelisted, template!(Word),
388 "the semantics of constant patterns is not yet settled",
391 may_dangle, Normal, template!(Word), dropck_eyepatch,
392 "`may_dangle` has unstable semantics and may be removed in the future",
395 // ==========================================================================
396 // Internal attributes: Runtime related:
397 // ==========================================================================
399 rustc_attr!(rustc_allocator, Whitelisted, template!(Word), IMPL_DETAIL),
400 rustc_attr!(rustc_allocator_nounwind, Whitelisted, template!(Word), IMPL_DETAIL),
401 gated!(alloc_error_handler, Normal, template!(Word), experimental!(alloc_error_handler)),
403 default_lib_allocator, Whitelisted, template!(Word), allocator_internals,
404 experimental!(default_lib_allocator),
407 needs_allocator, Normal, template!(Word), allocator_internals,
408 experimental!(needs_allocator),
410 gated!(panic_runtime, Whitelisted, template!(Word), experimental!(panic_runtime)),
411 gated!(needs_panic_runtime, Whitelisted, template!(Word), experimental!(needs_panic_runtime)),
413 unwind, Whitelisted, template!(List: "allowed|aborts"), unwind_attributes,
414 experimental!(unwind),
417 compiler_builtins, Whitelisted, template!(Word),
418 "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
419 which contains compiler-rt intrinsics and will never be stable",
422 profiler_runtime, Whitelisted, template!(Word),
423 "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
424 which contains the profiler runtime and will never be stable",
427 // ==========================================================================
428 // Internal attributes, Linkage:
429 // ==========================================================================
432 linkage, Whitelisted, template!(NameValueStr: "external|internal|..."),
433 "the `linkage` attribute is experimental and not portable across platforms",
435 rustc_attr!(rustc_std_internal_symbol, Whitelisted, template!(Word), INTERNAL_UNSTABLE),
437 // ==========================================================================
438 // Internal attributes, Macro related:
439 // ==========================================================================
441 rustc_attr!(rustc_builtin_macro, Whitelisted, template!(Word), IMPL_DETAIL),
442 rustc_attr!(rustc_proc_macro_decls, Normal, template!(Word), INTERNAL_UNSTABLE),
444 rustc_macro_transparency, Whitelisted,
445 template!(NameValueStr: "transparent|semitransparent|opaque"),
446 "used internally for testing macro hygiene",
449 // ==========================================================================
450 // Internal attributes, Diagnostics related:
451 // ==========================================================================
454 rustc_on_unimplemented, Whitelisted,
456 List: r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
457 NameValueStr: "message"
461 // Whitelists "identity-like" conversion methods to suggest on type mismatch.
462 rustc_attr!(rustc_conversion_suggestion, Whitelisted, template!(Word), INTERNAL_UNSTABLE),
464 // ==========================================================================
465 // Internal attributes, Const related:
466 // ==========================================================================
468 rustc_attr!(rustc_promotable, Whitelisted, template!(Word), IMPL_DETAIL),
469 rustc_attr!(rustc_allow_const_fn_ptr, Whitelisted, template!(Word), IMPL_DETAIL),
470 rustc_attr!(rustc_args_required_const, Whitelisted, template!(List: "N"), INTERNAL_UNSTABLE),
472 // ==========================================================================
473 // Internal attributes, Layout related:
474 // ==========================================================================
477 rustc_layout_scalar_valid_range_start, Whitelisted, template!(List: "value"),
478 "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
479 niche optimizations in libcore and will never be stable",
482 rustc_layout_scalar_valid_range_end, Whitelisted, template!(List: "value"),
483 "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
484 niche optimizations in libcore and will never be stable",
487 rustc_nonnull_optimization_guaranteed, Whitelisted, template!(Word),
488 "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
489 niche optimizations in libcore and will never be stable",
492 // ==========================================================================
493 // Internal attributes, Misc:
494 // ==========================================================================
496 lang, Normal, template!(NameValueStr: "name"), lang_items,
497 "language items are subject to change",
500 sym::rustc_diagnostic_item,
502 template!(NameValueStr: "name"),
506 "diagnostic items compiler internal support for linting",
507 cfg_fn!(rustc_attrs),
511 sym::no_debug, Whitelisted, template!(Word),
513 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
515 "the `#[no_debug]` attribute was an experimental feature that has been \
516 deprecated due to lack of demand",
522 prelude_import, Whitelisted, template!(Word),
523 "`#[prelude_import]` is for use by rustc only",
526 rustc_paren_sugar, Normal, template!(Word), unboxed_closures,
527 "unboxed_closures are still evolving",
530 rustc_inherit_overflow_checks, Whitelisted, template!(Word),
531 "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
532 overflow checking behavior of several libcore functions that are inlined \
533 across crates and will never be stable",
535 rustc_attr!(rustc_reservation_impl, Normal, template!(NameValueStr: "reservation message"),
536 "the `#[rustc_reservation_impl]` attribute is internally used \
537 for reserving for `for<T> From<!> for T` impl"
540 rustc_test_marker, Normal, template!(Word),
541 "the `#[rustc_test_marker]` attribute is used internally to track tests",
544 // ==========================================================================
545 // Internal attributes, Testing:
546 // ==========================================================================
548 rustc_attr!(TEST, rustc_outlives, Normal, template!(Word)),
549 rustc_attr!(TEST, rustc_variance, Normal, template!(Word)),
550 rustc_attr!(TEST, rustc_layout, Normal, template!(List: "field1, field2, ...")),
551 rustc_attr!(TEST, rustc_regions, Normal, template!(Word)),
553 TEST, rustc_error, Whitelisted,
554 template!(Word, List: "delay_span_bug_from_inside_query")
556 rustc_attr!(TEST, rustc_dump_user_substs, Whitelisted, template!(Word)),
557 rustc_attr!(TEST, rustc_if_this_changed, Whitelisted, template!(Word, List: "DepNode")),
558 rustc_attr!(TEST, rustc_then_this_would_need, Whitelisted, template!(List: "DepNode")),
560 TEST, rustc_dirty, Whitelisted,
561 template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
564 TEST, rustc_clean, Whitelisted,
565 template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
568 TEST, rustc_partition_reused, Whitelisted,
569 template!(List: r#"cfg = "...", module = "...""#),
572 TEST, rustc_partition_codegened, Whitelisted,
573 template!(List: r#"cfg = "...", module = "...""#),
576 TEST, rustc_expected_cgu_reuse, Whitelisted,
577 template!(List: r#"cfg = "...", module = "...", kind = "...""#),
579 rustc_attr!(TEST, rustc_synthetic, Whitelisted, template!(Word)),
580 rustc_attr!(TEST, rustc_symbol_name, Whitelisted, template!(Word)),
581 rustc_attr!(TEST, rustc_def_path, Whitelisted, template!(Word)),
582 rustc_attr!(TEST, rustc_mir, Whitelisted, template!(List: "arg1, arg2, ...")),
583 rustc_attr!(TEST, rustc_dump_program_clauses, Whitelisted, template!(Word)),
584 rustc_attr!(TEST, rustc_dump_env_program_clauses, Whitelisted, template!(Word)),
585 rustc_attr!(TEST, rustc_object_lifetime_default, Whitelisted, template!(Word)),
586 rustc_attr!(TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/)),
588 omit_gdb_pretty_printer_section, Whitelisted, template!(Word),
589 "the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
593 pub fn deprecated_attributes() -> Vec<&'static BuiltinAttribute> {
594 BUILTIN_ATTRIBUTES.iter().filter(|(.., gate)| gate.is_deprecated()).collect()
597 pub fn is_builtin_attr_name(name: Symbol) -> bool {
598 BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
602 pub static ref BUILTIN_ATTRIBUTE_MAP: FxHashMap<Symbol, &'static BuiltinAttribute> = {
603 let mut map = FxHashMap::default();
604 for attr in BUILTIN_ATTRIBUTES.iter() {
605 if map.insert(attr.0, attr).is_some() {
606 panic!("duplicate builtin attribute `{}`", attr.0);