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, Default)]
89 pub struct AttributeTemplate {
91 pub list: Option<&'static str>,
92 pub name_value_str: Option<&'static str>,
95 /// A convenience macro for constructing attribute templates.
96 /// E.g., `template!(Word, List: "description")` means that the attribute
97 /// supports forms `#[attr]` and `#[attr(description)]`.
98 macro_rules! template {
99 (Word) => { template!(@ true, None, None) };
100 (List: $descr: expr) => { template!(@ false, Some($descr), None) };
101 (NameValueStr: $descr: expr) => { template!(@ false, None, Some($descr)) };
102 (Word, List: $descr: expr) => { template!(@ true, Some($descr), None) };
103 (Word, NameValueStr: $descr: expr) => { template!(@ true, None, Some($descr)) };
104 (List: $descr1: expr, NameValueStr: $descr2: expr) => {
105 template!(@ false, Some($descr1), Some($descr2))
107 (Word, List: $descr1: expr, NameValueStr: $descr2: expr) => {
108 template!(@ true, Some($descr1), Some($descr2))
110 (@ $word: expr, $list: expr, $name_value_str: expr) => { AttributeTemplate {
111 word: $word, list: $list, name_value_str: $name_value_str
115 macro_rules! ungated {
116 ($attr:ident, $typ:expr, $tpl:expr $(,)?) => {
117 (sym::$attr, $typ, $tpl, Ungated)
122 ($attr:ident, $typ:expr, $tpl:expr, $gate:ident, $msg:expr $(,)?) => {
123 (sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$gate, $msg, cfg_fn!($gate)))
125 ($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
126 (sym::$attr, $typ, $tpl, Gated(Stability::Unstable, sym::$attr, $msg, cfg_fn!($attr)))
130 macro_rules! rustc_attr {
131 (TEST, $attr:ident, $typ:expr, $tpl:expr $(,)?) => {
139 "]` attribute is just used for rustc unit tests \
140 and will never be stable",
144 ($attr:ident, $typ:expr, $tpl:expr, $msg:expr $(,)?) => {
149 Gated(Stability::Unstable, sym::rustc_attrs, $msg, cfg_fn!(rustc_attrs)),
154 macro_rules! experimental {
156 concat!("the `#[", stringify!($attr), "]` attribute is an experimental feature")
160 const IMPL_DETAIL: &str = "internal implementation detail";
161 const INTERNAL_UNSTABLE: &str = "this is an internal attribute that will never be stable";
163 pub type BuiltinAttribute = (Symbol, AttributeType, AttributeTemplate, AttributeGate);
165 /// Attributes that have a special meaning to rustc or rustdoc.
167 pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
168 // ==========================================================================
169 // Stable attributes:
170 // ==========================================================================
172 // Conditional compilation:
173 ungated!(cfg, Normal, template!(List: "predicate")),
174 ungated!(cfg_attr, Normal, template!(List: "predicate, attr1, attr2, ...")),
177 ungated!(ignore, Normal, template!(Word, NameValueStr: "reason")),
179 should_panic, Normal,
180 template!(Word, List: r#"expected = "reason"#, NameValueStr: "reason"),
182 // FIXME(Centril): This can be used on stable but shouldn't.
183 ungated!(reexport_test_harness_main, Normal, template!(NameValueStr: "name")),
186 ungated!(derive, Normal, template!(List: "Trait1, Trait2, ...")),
187 ungated!(automatically_derived, Normal, template!(Word)),
189 ungated!(macro_use, Normal, template!(Word, List: "name1, name2, ...")),
190 ungated!(macro_escape, Normal, template!(Word)), // Deprecated synonym for `macro_use`.
191 ungated!(macro_export, Normal, template!(Word, List: "local_inner_macros")),
192 ungated!(proc_macro, Normal, template!(Word)),
194 proc_macro_derive, Normal,
195 template!(List: "TraitName, /*opt*/ attributes(name1, name2, ...)"),
197 ungated!(proc_macro_attribute, Normal, template!(Word)),
200 ungated!(warn, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
201 ungated!(allow, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
202 ungated!(forbid, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
203 ungated!(deny, Normal, template!(List: r#"lint1, lint2, ..., /*opt*/ reason = "...""#)),
204 ungated!(must_use, Whitelisted, template!(Word, NameValueStr: "reason")),
210 List: r#"/*opt*/ since = "version", /*opt*/ note = "reason""#,
211 NameValueStr: "reason"
216 ungated!(crate_name, CrateLevel, template!(NameValueStr: "name")),
217 ungated!(crate_type, CrateLevel, template!(NameValueStr: "bin|lib|...")),
218 ungated!(crate_id, CrateLevel, template!(NameValueStr: "ignored")),
220 // ABI, linking, symbols, and FFI
223 template!(List: r#"name = "...", /*opt*/ kind = "dylib|static|...", /*opt*/ wasm_import_module = "...""#),
225 ungated!(link_name, Whitelisted, template!(NameValueStr: "name")),
226 ungated!(no_link, Normal, template!(Word)),
227 ungated!(repr, Normal, template!(List: "C")),
228 ungated!(export_name, Whitelisted, template!(NameValueStr: "name")),
229 ungated!(link_section, Whitelisted, template!(NameValueStr: "name")),
230 ungated!(no_mangle, Whitelisted, template!(Word)),
231 ungated!(used, Whitelisted, template!(Word)),
234 ungated!(recursion_limit, CrateLevel, template!(NameValueStr: "N")),
235 ungated!(type_length_limit, CrateLevel, template!(NameValueStr: "N")),
237 const_eval_limit, CrateLevel, template!(NameValueStr: "N"), const_eval_limit,
238 experimental!(const_eval_limit)
242 ungated!(main, Normal, template!(Word)),
243 ungated!(start, Normal, template!(Word)),
244 ungated!(no_start, CrateLevel, template!(Word)),
245 ungated!(no_main, CrateLevel, template!(Word)),
247 // Modules, prelude, and resolution:
248 ungated!(path, Normal, template!(NameValueStr: "file")),
249 ungated!(no_std, CrateLevel, template!(Word)),
250 ungated!(no_implicit_prelude, Normal, template!(Word)),
251 ungated!(non_exhaustive, Whitelisted, template!(Word)),
254 ungated!(windows_subsystem, Whitelisted, template!(NameValueStr: "windows|console")),
255 ungated!(panic_handler, Normal, template!(Word)), // RFC 2070
258 ungated!(inline, Whitelisted, template!(Word, List: "always|never")),
259 ungated!(cold, Whitelisted, template!(Word)),
260 ungated!(no_builtins, Whitelisted, template!(Word)),
261 ungated!(target_feature, Whitelisted, template!(List: r#"enable = "name""#)),
263 no_sanitize, Whitelisted,
264 template!(List: "address, memory, thread"),
265 experimental!(no_sanitize)
268 // FIXME: #14408 whitelist docs since rustdoc looks at them
269 ungated!(doc, Whitelisted, template!(List: "hidden|inline|...", NameValueStr: "string")),
271 // ==========================================================================
272 // Unstable attributes:
273 // ==========================================================================
276 gated!(naked, Whitelisted, template!(Word), naked_functions, experimental!(naked)),
278 link_args, Normal, template!(NameValueStr: "args"),
279 "the `link_args` attribute is experimental and not portable across platforms, \
280 it is recommended to use `#[link(name = \"foo\")] instead",
283 link_ordinal, Whitelisted, template!(List: "ordinal"), raw_dylib,
284 experimental!(link_ordinal)
289 sym::plugin_registrar, Normal, template!(Word),
291 Stability::Deprecated(
292 "https://github.com/rust-lang/rust/pull/64675",
293 Some("may be removed in a future compiler version"),
295 sym::plugin_registrar,
296 "compiler plugins are deprecated",
297 cfg_fn!(plugin_registrar)
301 sym::plugin, CrateLevel, template!(List: "name"),
303 Stability::Deprecated(
304 "https://github.com/rust-lang/rust/pull/64675",
305 Some("may be removed in a future compiler version"),
308 "compiler plugins are deprecated",
314 gated!(allow_fail, Normal, template!(Word), experimental!(allow_fail)),
316 test_runner, CrateLevel, template!(List: "path"), custom_test_frameworks,
317 "custom test frameworks are an unstable feature",
320 gated!(marker, Normal, template!(Word), marker_trait_attr, experimental!(marker)),
322 thread_local, Whitelisted, template!(Word),
323 "`#[thread_local]` is an experimental feature, and does not currently handle destructors",
325 gated!(no_core, CrateLevel, template!(Word), experimental!(no_core)),
328 optimize, Whitelisted, template!(List: "size|speed"), optimize_attribute,
329 experimental!(optimize),
332 gated!(ffi_returns_twice, Whitelisted, template!(Word), experimental!(ffi_returns_twice)),
333 gated!(track_caller, Whitelisted, template!(Word), experimental!(track_caller)),
335 register_attr, CrateLevel, template!(List: "attr1, attr2, ..."),
336 experimental!(register_attr),
339 register_tool, CrateLevel, template!(List: "tool1, tool2, ..."),
340 experimental!(register_tool),
343 // ==========================================================================
344 // Internal attributes: Stability, deprecation, and unsafe:
345 // ==========================================================================
347 ungated!(feature, CrateLevel, template!(List: "name1, name1, ...")),
348 // FIXME(#14407) -- only looked at on-demand so we can't
349 // guarantee they'll have already been checked.
351 rustc_deprecated, Whitelisted,
352 template!(List: r#"since = "version", reason = "...""#)
355 ungated!(stable, Whitelisted, template!(List: r#"feature = "name", since = "version""#)),
358 unstable, Whitelisted,
359 template!(List: r#"feature = "name", reason = "...", issue = "N""#),
362 ungated!(rustc_const_unstable, Whitelisted, template!(List: r#"feature = "name""#)),
364 ungated!(rustc_const_stable, Whitelisted, template!(List: r#"feature = "name""#)),
366 allow_internal_unstable, Normal, template!(Word, List: "feat1, feat2, ..."),
367 "allow_internal_unstable side-steps feature gating and stability checks",
370 allow_internal_unsafe, Normal, template!(Word),
371 "allow_internal_unsafe side-steps the unsafe_code lint",
374 // ==========================================================================
375 // Internal attributes: Type system related:
376 // ==========================================================================
378 gated!(fundamental, Whitelisted, template!(Word), experimental!(fundamental)),
380 may_dangle, Normal, template!(Word), dropck_eyepatch,
381 "`may_dangle` has unstable semantics and may be removed in the future",
384 // ==========================================================================
385 // Internal attributes: Runtime related:
386 // ==========================================================================
388 rustc_attr!(rustc_allocator, Whitelisted, template!(Word), IMPL_DETAIL),
389 rustc_attr!(rustc_allocator_nounwind, Whitelisted, template!(Word), IMPL_DETAIL),
390 gated!(alloc_error_handler, Normal, template!(Word), experimental!(alloc_error_handler)),
392 default_lib_allocator, Whitelisted, template!(Word), allocator_internals,
393 experimental!(default_lib_allocator),
396 needs_allocator, Normal, template!(Word), allocator_internals,
397 experimental!(needs_allocator),
399 gated!(panic_runtime, Whitelisted, template!(Word), experimental!(panic_runtime)),
400 gated!(needs_panic_runtime, Whitelisted, template!(Word), experimental!(needs_panic_runtime)),
402 unwind, Whitelisted, template!(List: "allowed|aborts"), unwind_attributes,
403 experimental!(unwind),
406 compiler_builtins, Whitelisted, template!(Word),
407 "the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate \
408 which contains compiler-rt intrinsics and will never be stable",
411 profiler_runtime, Whitelisted, template!(Word),
412 "the `#[profiler_runtime]` attribute is used to identify the `profiler_builtins` crate \
413 which contains the profiler runtime and will never be stable",
416 // ==========================================================================
417 // Internal attributes, Linkage:
418 // ==========================================================================
421 linkage, Whitelisted, template!(NameValueStr: "external|internal|..."),
422 "the `linkage` attribute is experimental and not portable across platforms",
424 rustc_attr!(rustc_std_internal_symbol, Whitelisted, template!(Word), INTERNAL_UNSTABLE),
426 // ==========================================================================
427 // Internal attributes, Macro related:
428 // ==========================================================================
430 rustc_attr!(rustc_builtin_macro, Whitelisted, template!(Word), IMPL_DETAIL),
431 rustc_attr!(rustc_proc_macro_decls, Normal, template!(Word), INTERNAL_UNSTABLE),
433 rustc_macro_transparency, Whitelisted,
434 template!(NameValueStr: "transparent|semitransparent|opaque"),
435 "used internally for testing macro hygiene",
438 // ==========================================================================
439 // Internal attributes, Diagnostics related:
440 // ==========================================================================
443 rustc_on_unimplemented, Whitelisted,
445 List: r#"/*opt*/ message = "...", /*opt*/ label = "...", /*opt*/ note = "...""#,
446 NameValueStr: "message"
450 // Whitelists "identity-like" conversion methods to suggest on type mismatch.
451 rustc_attr!(rustc_conversion_suggestion, Whitelisted, template!(Word), INTERNAL_UNSTABLE),
453 // ==========================================================================
454 // Internal attributes, Const related:
455 // ==========================================================================
457 rustc_attr!(rustc_promotable, Whitelisted, template!(Word), IMPL_DETAIL),
458 rustc_attr!(rustc_allow_const_fn_ptr, Whitelisted, template!(Word), IMPL_DETAIL),
459 rustc_attr!(rustc_args_required_const, Whitelisted, template!(List: "N"), INTERNAL_UNSTABLE),
461 // ==========================================================================
462 // Internal attributes, Layout related:
463 // ==========================================================================
466 rustc_layout_scalar_valid_range_start, Whitelisted, template!(List: "value"),
467 "the `#[rustc_layout_scalar_valid_range_start]` attribute is just used to enable \
468 niche optimizations in libcore and will never be stable",
471 rustc_layout_scalar_valid_range_end, Whitelisted, template!(List: "value"),
472 "the `#[rustc_layout_scalar_valid_range_end]` attribute is just used to enable \
473 niche optimizations in libcore and will never be stable",
476 rustc_nonnull_optimization_guaranteed, Whitelisted, template!(Word),
477 "the `#[rustc_nonnull_optimization_guaranteed]` attribute is just used to enable \
478 niche optimizations in libcore and will never be stable",
481 // ==========================================================================
482 // Internal attributes, Misc:
483 // ==========================================================================
485 lang, Normal, template!(NameValueStr: "name"), lang_items,
486 "language items are subject to change",
489 sym::rustc_diagnostic_item,
491 template!(NameValueStr: "name"),
495 "diagnostic items compiler internal support for linting",
496 cfg_fn!(rustc_attrs),
501 prelude_import, Whitelisted, template!(Word),
502 "`#[prelude_import]` is for use by rustc only",
505 rustc_paren_sugar, Normal, template!(Word), unboxed_closures,
506 "unboxed_closures are still evolving",
509 rustc_inherit_overflow_checks, Whitelisted, template!(Word),
510 "the `#[rustc_inherit_overflow_checks]` attribute is just used to control \
511 overflow checking behavior of several libcore functions that are inlined \
512 across crates and will never be stable",
514 rustc_attr!(rustc_reservation_impl, Normal, template!(NameValueStr: "reservation message"),
515 "the `#[rustc_reservation_impl]` attribute is internally used \
516 for reserving for `for<T> From<!> for T` impl"
519 rustc_test_marker, Normal, template!(Word),
520 "the `#[rustc_test_marker]` attribute is used internally to track tests",
523 rustc_unsafe_specialization_marker, Normal, template!(Word),
524 "the `#[rustc_unsafe_specialization_marker]` attribute is used to check specializations"
527 rustc_specialization_trait, Normal, template!(Word),
528 "the `#[rustc_specialization_trait]` attribute is used to check specializations"
531 // ==========================================================================
532 // Internal attributes, Testing:
533 // ==========================================================================
535 rustc_attr!(TEST, rustc_outlives, Normal, template!(Word)),
536 rustc_attr!(TEST, rustc_variance, Normal, template!(Word)),
537 rustc_attr!(TEST, rustc_layout, Normal, template!(List: "field1, field2, ...")),
538 rustc_attr!(TEST, rustc_regions, Normal, template!(Word)),
540 TEST, rustc_error, Whitelisted,
541 template!(Word, List: "delay_span_bug_from_inside_query")
543 rustc_attr!(TEST, rustc_dump_user_substs, Whitelisted, template!(Word)),
544 rustc_attr!(TEST, rustc_if_this_changed, Whitelisted, template!(Word, List: "DepNode")),
545 rustc_attr!(TEST, rustc_then_this_would_need, Whitelisted, template!(List: "DepNode")),
547 TEST, rustc_dirty, Whitelisted,
548 template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
551 TEST, rustc_clean, Whitelisted,
552 template!(List: r#"cfg = "...", /*opt*/ label = "...", /*opt*/ except = "...""#),
555 TEST, rustc_partition_reused, Whitelisted,
556 template!(List: r#"cfg = "...", module = "...""#),
559 TEST, rustc_partition_codegened, Whitelisted,
560 template!(List: r#"cfg = "...", module = "...""#),
563 TEST, rustc_expected_cgu_reuse, Whitelisted,
564 template!(List: r#"cfg = "...", module = "...", kind = "...""#),
566 rustc_attr!(TEST, rustc_synthetic, Whitelisted, template!(Word)),
567 rustc_attr!(TEST, rustc_symbol_name, Whitelisted, template!(Word)),
568 rustc_attr!(TEST, rustc_def_path, Whitelisted, template!(Word)),
569 rustc_attr!(TEST, rustc_mir, Whitelisted, template!(List: "arg1, arg2, ...")),
570 rustc_attr!(TEST, rustc_dump_program_clauses, Whitelisted, template!(Word)),
571 rustc_attr!(TEST, rustc_dump_env_program_clauses, Whitelisted, template!(Word)),
572 rustc_attr!(TEST, rustc_object_lifetime_default, Whitelisted, template!(Word)),
573 rustc_attr!(TEST, rustc_dummy, Normal, template!(Word /* doesn't matter*/)),
575 omit_gdb_pretty_printer_section, Whitelisted, template!(Word),
576 "the `#[omit_gdb_pretty_printer_section]` attribute is just used for the Rust test suite",
580 pub fn deprecated_attributes() -> Vec<&'static BuiltinAttribute> {
581 BUILTIN_ATTRIBUTES.iter().filter(|(.., gate)| gate.is_deprecated()).collect()
584 pub fn is_builtin_attr_name(name: Symbol) -> bool {
585 BUILTIN_ATTRIBUTE_MAP.get(&name).is_some()
589 pub static ref BUILTIN_ATTRIBUTE_MAP: FxHashMap<Symbol, &'static BuiltinAttribute> = {
590 let mut map = FxHashMap::default();
591 for attr in BUILTIN_ATTRIBUTES.iter() {
592 if map.insert(attr.0, attr).is_some() {
593 panic!("duplicate builtin attribute `{}`", attr.0);