rustc_feature/unstable.rs
1//! List of the unstable feature gates.
2
3use std::path::PathBuf;
4use std::time::{SystemTime, UNIX_EPOCH};
5
6use rustc_data_structures::fx::FxHashSet;
7use rustc_span::{Span, Symbol, sym};
8
9use super::{Feature, to_nonzero};
10
11#[derive(PartialEq)]
12enum FeatureStatus {
13 Default,
14 Incomplete,
15 Internal,
16}
17
18macro_rules! status_to_enum {
19 (unstable) => {
20 FeatureStatus::Default
21 };
22 (incomplete) => {
23 FeatureStatus::Incomplete
24 };
25 (internal) => {
26 FeatureStatus::Internal
27 };
28}
29
30/// A set of features to be used by later passes.
31///
32/// There are two ways to check if a language feature `foo` is enabled:
33/// - Directly with the `foo` method, e.g. `if tcx.features().foo() { ... }`.
34/// - With the `enabled` method, e.g. `if tcx.features.enabled(sym::foo) { ... }`.
35///
36/// The former is preferred. `enabled` should only be used when the feature symbol is not a
37/// constant, e.g. a parameter, or when the feature is a library feature.
38#[derive(Clone, Default, Debug)]
39pub struct Features {
40 /// `#![feature]` attrs for language features, for error reporting.
41 enabled_lang_features: Vec<EnabledLangFeature>,
42 /// `#![feature]` attrs for non-language (library) features.
43 enabled_lib_features: Vec<EnabledLibFeature>,
44 /// `enabled_lang_features` + `enabled_lib_features`.
45 enabled_features: FxHashSet<Symbol>,
46}
47
48/// Information about an enabled language feature.
49#[derive(Debug, Copy, Clone)]
50pub struct EnabledLangFeature {
51 /// Name of the feature gate guarding the language feature.
52 pub gate_name: Symbol,
53 /// Span of the `#[feature(...)]` attribute.
54 pub attr_sp: Span,
55 /// If the lang feature is stable, the version number when it was stabilized.
56 pub stable_since: Option<Symbol>,
57}
58
59/// Information about an enabled library feature.
60#[derive(Debug, Copy, Clone)]
61pub struct EnabledLibFeature {
62 pub gate_name: Symbol,
63 pub attr_sp: Span,
64}
65
66impl Features {
67 /// `since` should be set for stable features that are nevertheless enabled with a `#[feature]`
68 /// attribute, indicating since when they are stable.
69 pub fn set_enabled_lang_feature(&mut self, lang_feat: EnabledLangFeature) {
70 self.enabled_lang_features.push(lang_feat);
71 self.enabled_features.insert(lang_feat.gate_name);
72 }
73
74 pub fn set_enabled_lib_feature(&mut self, lib_feat: EnabledLibFeature) {
75 self.enabled_lib_features.push(lib_feat);
76 self.enabled_features.insert(lib_feat.gate_name);
77 }
78
79 /// Returns a list of [`EnabledLangFeature`] with info about:
80 ///
81 /// - Feature gate name.
82 /// - The span of the `#[feature]` attribute.
83 /// - For stable language features, version info for when it was stabilized.
84 pub fn enabled_lang_features(&self) -> &Vec<EnabledLangFeature> {
85 &self.enabled_lang_features
86 }
87
88 pub fn enabled_lib_features(&self) -> &Vec<EnabledLibFeature> {
89 &self.enabled_lib_features
90 }
91
92 pub fn enabled_features(&self) -> &FxHashSet<Symbol> {
93 &self.enabled_features
94 }
95
96 /// Is the given feature enabled (via `#[feature(...)]`)?
97 pub fn enabled(&self, feature: Symbol) -> bool {
98 self.enabled_features.contains(&feature)
99 }
100}
101
102macro_rules! declare_features {
103 ($(
104 $(#[doc = $doc:tt])* ($status:ident, $feature:ident, $ver:expr, $issue:expr),
105 )+) => {
106 /// Unstable language features that are being implemented or being
107 /// considered for acceptance (stabilization) or removal.
108 pub static UNSTABLE_LANG_FEATURES: &[Feature] = &[
109 $(Feature {
110 name: sym::$feature,
111 since: $ver,
112 issue: to_nonzero($issue),
113 }),+
114 ];
115
116 impl Features {
117 $(
118 pub fn $feature(&self) -> bool {
119 self.enabled_features.contains(&sym::$feature)
120 }
121 )*
122
123 /// Some features are known to be incomplete and using them is likely to have
124 /// unanticipated results, such as compiler crashes. We warn the user about these
125 /// to alert them.
126 pub fn incomplete(&self, feature: Symbol) -> bool {
127 match feature {
128 $(
129 sym::$feature => status_to_enum!($status) == FeatureStatus::Incomplete,
130 )*
131 _ if self.enabled_features.contains(&feature) => {
132 // Accepted/removed features and library features aren't in this file but
133 // are never incomplete.
134 false
135 }
136 _ => panic!("`{}` was not listed in `declare_features`", feature),
137 }
138 }
139
140 /// Some features are internal to the compiler and standard library and should not
141 /// be used in normal projects. We warn the user about these to alert them.
142 pub fn internal(&self, feature: Symbol) -> bool {
143 match feature {
144 $(
145 sym::$feature => status_to_enum!($status) == FeatureStatus::Internal,
146 )*
147 _ if self.enabled_features.contains(&feature) => {
148 // This could be accepted/removed, or a libs feature.
149 // Accepted/removed features aren't in this file but are never internal
150 // (a removed feature might have been internal, but that's now irrelevant).
151 // Libs features are internal if they end in `_internal` or `_internals`.
152 // As a special exception we also consider `core_intrinsics` internal;
153 // renaming that age-old feature is just not worth the hassle.
154 // We just always test the name; it's not a big deal if we accidentally hit
155 // an accepted/removed lang feature that way.
156 let name = feature.as_str();
157 name == "core_intrinsics" || name.ends_with("_internal") || name.ends_with("_internals")
158 }
159 _ => panic!("`{}` was not listed in `declare_features`", feature),
160 }
161 }
162 }
163 };
164}
165
166// See https://rustc-dev-guide.rust-lang.org/feature-gates.html#feature-gates for more
167// documentation about handling feature gates.
168//
169// If you change this, please modify `src/doc/unstable-book` as well.
170//
171// Don't ever remove anything from this list; move them to `accepted.rs` if
172// accepted or `removed.rs` if removed.
173//
174// The version numbers here correspond to the version in which the current status
175// was set.
176//
177// Note that the features are grouped into internal/user-facing and then
178// sorted alphabetically inside those groups. This is enforced with tidy.
179//
180// N.B., `tools/tidy/src/features.rs` parses this information directly out of the
181// source, so take care when modifying it.
182
183#[rustfmt::skip]
184declare_features! (
185 // -------------------------------------------------------------------------
186 // feature-group-start: internal feature gates (no tracking issue)
187 // -------------------------------------------------------------------------
188 // no-tracking-issue-start
189
190 /// Allows using the `unadjusted` ABI; perma-unstable.
191 (internal, abi_unadjusted, "1.16.0", None),
192 /// Allows using `#![needs_allocator]`, an implementation detail of `#[global_allocator]`.
193 (internal, allocator_internals, "1.20.0", None),
194 /// Allows using `#[allow_internal_unsafe]`. This is an
195 /// attribute on `macro_rules!` and can't use the attribute handling
196 /// below (it has to be checked before expansion possibly makes
197 /// macros disappear).
198 (internal, allow_internal_unsafe, "1.0.0", None),
199 /// Allows using `#[allow_internal_unstable]`. This is an
200 /// attribute on `macro_rules!` and can't use the attribute handling
201 /// below (it has to be checked before expansion possibly makes
202 /// macros disappear).
203 (internal, allow_internal_unstable, "1.0.0", None),
204 /// Allows using anonymous lifetimes in argument-position impl-trait.
205 (unstable, anonymous_lifetime_in_impl_trait, "1.63.0", None),
206 /// Allows access to the emscripten_wasm_eh config, used by panic_unwind and unwind
207 (internal, cfg_emscripten_wasm_eh, "1.86.0", None),
208 /// Allows checking whether or not the backend correctly supports unstable float types.
209 (internal, cfg_target_has_reliable_f16_f128, "1.88.0", None),
210 /// Allows identifying the `compiler_builtins` crate.
211 (internal, compiler_builtins, "1.13.0", None),
212 /// Allows writing custom MIR
213 (internal, custom_mir, "1.65.0", None),
214 /// Outputs useful `assert!` messages
215 (unstable, generic_assert, "1.63.0", None),
216 /// Allows using the #[rustc_intrinsic] attribute.
217 (internal, intrinsics, "1.0.0", None),
218 /// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic.
219 (internal, lang_items, "1.0.0", None),
220 /// Allows `#[link(..., cfg(..))]`; perma-unstable per #37406
221 (internal, link_cfg, "1.14.0", None),
222 /// Allows using `?Trait` trait bounds in more contexts.
223 (internal, more_maybe_bounds, "1.82.0", None),
224 /// Allows the `multiple_supertrait_upcastable` lint.
225 (unstable, multiple_supertrait_upcastable, "1.69.0", None),
226 /// Allow negative trait bounds. This is an internal-only feature for testing the trait solver!
227 (internal, negative_bounds, "1.71.0", None),
228 /// Allows using `#[omit_gdb_pretty_printer_section]`.
229 (internal, omit_gdb_pretty_printer_section, "1.5.0", None),
230 /// Set the maximum pattern complexity allowed (not limited by default).
231 (internal, pattern_complexity_limit, "1.78.0", None),
232 /// Allows using pattern types.
233 (internal, pattern_types, "1.79.0", Some(123646)),
234 /// Allows using `#[prelude_import]` on glob `use` items.
235 (internal, prelude_import, "1.2.0", None),
236 /// Used to identify crates that contain the profiler runtime.
237 (internal, profiler_runtime, "1.18.0", None),
238 /// Allows using `rustc_*` attributes (RFC 572).
239 (internal, rustc_attrs, "1.0.0", None),
240 /// Allows using the `#[stable]` and `#[unstable]` attributes.
241 (internal, staged_api, "1.0.0", None),
242 /// Added for testing unstable lints; perma-unstable.
243 (internal, test_unstable_lint, "1.60.0", None),
244 /// Helps with formatting for `group_imports = "StdExternalCrate"`.
245 (unstable, unqualified_local_imports, "1.83.0", Some(138299)),
246 /// Use for stable + negative coherence and strict coherence depending on trait's
247 /// rustc_strict_coherence value.
248 (unstable, with_negative_coherence, "1.60.0", None),
249 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
250 // Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
251 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
252
253 // no-tracking-issue-end
254 // -------------------------------------------------------------------------
255 // feature-group-end: internal feature gates (no tracking issue)
256 // -------------------------------------------------------------------------
257
258 // -------------------------------------------------------------------------
259 // feature-group-start: internal feature gates
260 // -------------------------------------------------------------------------
261
262 /// Allows using the `vectorcall` ABI.
263 (unstable, abi_vectorcall, "1.7.0", Some(124485)),
264 /// Allows features specific to auto traits.
265 /// Renamed from `optin_builtin_traits`.
266 (unstable, auto_traits, "1.50.0", Some(13231)),
267 /// Allows using `box` in patterns (RFC 469).
268 (unstable, box_patterns, "1.0.0", Some(29641)),
269 /// Allows builtin # foo() syntax
270 (internal, builtin_syntax, "1.71.0", Some(110680)),
271 /// Allows `#[doc(notable_trait)]`.
272 /// Renamed from `doc_spotlight`.
273 (unstable, doc_notable_trait, "1.52.0", Some(45040)),
274 /// Allows using the `may_dangle` attribute (RFC 1327).
275 (unstable, dropck_eyepatch, "1.10.0", Some(34761)),
276 /// Allows using the `#[fundamental]` attribute.
277 (unstable, fundamental, "1.0.0", Some(29635)),
278 /// Allows using `#[link_name="llvm.*"]`.
279 (internal, link_llvm_intrinsics, "1.0.0", Some(29602)),
280 /// Allows using the `#[linkage = ".."]` attribute.
281 (unstable, linkage, "1.0.0", Some(29603)),
282 /// Allows declaring with `#![needs_panic_runtime]` that a panic runtime is needed.
283 (internal, needs_panic_runtime, "1.10.0", Some(32837)),
284 /// Allows using the `#![panic_runtime]` attribute.
285 (internal, panic_runtime, "1.10.0", Some(32837)),
286 /// Allows using `#[rustc_allow_const_fn_unstable]`.
287 /// This is an attribute on `const fn` for the same
288 /// purpose as `#[allow_internal_unstable]`.
289 (internal, rustc_allow_const_fn_unstable, "1.49.0", Some(69399)),
290 /// Allows using compiler's own crates.
291 (unstable, rustc_private, "1.0.0", Some(27812)),
292 /// Allows using internal rustdoc features like `doc(keyword)`.
293 (internal, rustdoc_internals, "1.58.0", Some(90418)),
294 /// Allows using the `rustdoc::missing_doc_code_examples` lint
295 (unstable, rustdoc_missing_doc_code_examples, "1.31.0", Some(101730)),
296 /// Allows using `#[structural_match]` which indicates that a type is structurally matchable.
297 /// FIXME: Subsumed by trait `StructuralPartialEq`, cannot move to removed until a library
298 /// feature with the same name exists.
299 (unstable, structural_match, "1.8.0", Some(31434)),
300 /// Allows using the `rust-call` ABI.
301 (unstable, unboxed_closures, "1.0.0", Some(29625)),
302 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
303 // Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
304 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
305
306 // -------------------------------------------------------------------------
307 // feature-group-end: internal feature gates
308 // -------------------------------------------------------------------------
309
310 // -------------------------------------------------------------------------
311 // feature-group-start: actual feature gates (target features)
312 // -------------------------------------------------------------------------
313
314 // FIXME: Document these and merge with the list below.
315
316 // Unstable `#[target_feature]` directives.
317 (unstable, aarch64_unstable_target_feature, "1.82.0", Some(44839)),
318 (unstable, aarch64_ver_target_feature, "1.27.0", Some(44839)),
319 (unstable, apx_target_feature, "1.88.0", Some(139284)),
320 (unstable, arm_target_feature, "1.27.0", Some(44839)),
321 (unstable, bpf_target_feature, "1.54.0", Some(44839)),
322 (unstable, csky_target_feature, "1.73.0", Some(44839)),
323 (unstable, ermsb_target_feature, "1.49.0", Some(44839)),
324 (unstable, hexagon_target_feature, "1.27.0", Some(44839)),
325 (unstable, lahfsahf_target_feature, "1.78.0", Some(44839)),
326 (unstable, loongarch_target_feature, "1.73.0", Some(44839)),
327 (unstable, m68k_target_feature, "1.85.0", Some(134328)),
328 (unstable, mips_target_feature, "1.27.0", Some(44839)),
329 (unstable, movrs_target_feature, "1.88.0", Some(137976)),
330 (unstable, powerpc_target_feature, "1.27.0", Some(44839)),
331 (unstable, prfchw_target_feature, "1.78.0", Some(44839)),
332 (unstable, riscv_target_feature, "1.45.0", Some(44839)),
333 (unstable, rtm_target_feature, "1.35.0", Some(44839)),
334 (unstable, s390x_target_feature, "1.82.0", Some(44839)),
335 (unstable, sparc_target_feature, "1.84.0", Some(132783)),
336 (unstable, sse4a_target_feature, "1.27.0", Some(44839)),
337 (unstable, tbm_target_feature, "1.27.0", Some(44839)),
338 (unstable, wasm_target_feature, "1.30.0", Some(44839)),
339 (unstable, x87_target_feature, "1.85.0", Some(44839)),
340 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
341 // Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
342 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
343
344 // -------------------------------------------------------------------------
345 // feature-group-end: actual feature gates (target features)
346 // -------------------------------------------------------------------------
347
348 // -------------------------------------------------------------------------
349 // feature-group-start: actual feature gates
350 // -------------------------------------------------------------------------
351
352 /// Allows `extern "avr-interrupt" fn()` and `extern "avr-non-blocking-interrupt" fn()`.
353 (unstable, abi_avr_interrupt, "1.45.0", Some(69664)),
354 /// Allows `extern "C-cmse-nonsecure-call" fn()`.
355 (unstable, abi_c_cmse_nonsecure_call, "1.51.0", Some(81391)),
356 /// Allows `extern "gpu-kernel" fn()`.
357 (unstable, abi_gpu_kernel, "1.86.0", Some(135467)),
358 /// Allows `extern "msp430-interrupt" fn()`.
359 (unstable, abi_msp430_interrupt, "1.16.0", Some(38487)),
360 /// Allows `extern "ptx-*" fn()`.
361 (unstable, abi_ptx, "1.15.0", Some(38788)),
362 /// Allows `extern "riscv-interrupt-m" fn()` and `extern "riscv-interrupt-s" fn()`.
363 (unstable, abi_riscv_interrupt, "1.73.0", Some(111889)),
364 /// Allows `extern "x86-interrupt" fn()`.
365 (unstable, abi_x86_interrupt, "1.17.0", Some(40180)),
366 /// Allows additional const parameter types, such as `[u8; 10]` or user defined types
367 (unstable, adt_const_params, "1.56.0", Some(95174)),
368 /// Allows defining an `#[alloc_error_handler]`.
369 (unstable, alloc_error_handler, "1.29.0", Some(51540)),
370 /// Allows inherent and trait methods with arbitrary self types.
371 (unstable, arbitrary_self_types, "1.23.0", Some(44874)),
372 /// Allows inherent and trait methods with arbitrary self types that are raw pointers.
373 (unstable, arbitrary_self_types_pointers, "1.83.0", Some(44874)),
374 /// Enables experimental inline assembly support for additional architectures.
375 (unstable, asm_experimental_arch, "1.58.0", Some(93335)),
376 /// Enables experimental register support in inline assembly.
377 (unstable, asm_experimental_reg, "1.85.0", Some(133416)),
378 /// Allows using `label` operands in inline assembly together with output operands.
379 (unstable, asm_goto_with_outputs, "1.85.0", Some(119364)),
380 /// Allows the `may_unwind` option in inline assembly.
381 (unstable, asm_unwind, "1.58.0", Some(93334)),
382 /// Allows users to enforce equality of associated constants `TraitImpl<AssocConst=3>`.
383 (unstable, associated_const_equality, "1.58.0", Some(92827)),
384 /// Allows associated type defaults.
385 (unstable, associated_type_defaults, "1.2.0", Some(29661)),
386 /// Allows implementing `AsyncDrop`.
387 (incomplete, async_drop, "1.88.0", Some(126482)),
388 /// Allows async functions to be called from `dyn Trait`.
389 (incomplete, async_fn_in_dyn_trait, "1.85.0", Some(133119)),
390 /// Allows `#[track_caller]` on async functions.
391 (unstable, async_fn_track_caller, "1.73.0", Some(110011)),
392 /// Allows `for await` loops.
393 (unstable, async_for_loop, "1.77.0", Some(118898)),
394 /// Allows `async` trait bound modifier.
395 (unstable, async_trait_bounds, "1.85.0", Some(62290)),
396 /// Allows using Intel AVX10 target features and intrinsics
397 (unstable, avx10_target_feature, "1.88.0", Some(138843)),
398 /// Allows using C-variadics.
399 (unstable, c_variadic, "1.34.0", Some(44930)),
400 /// Allows the use of `#[cfg(contract_checks)` to check if contract checks are enabled.
401 (unstable, cfg_contract_checks, "1.86.0", Some(128044)),
402 /// Allows the use of `#[cfg(overflow_checks)` to check if integer overflow behaviour.
403 (unstable, cfg_overflow_checks, "1.71.0", Some(111466)),
404 /// Provides the relocation model information as cfg entry
405 (unstable, cfg_relocation_model, "1.73.0", Some(114929)),
406 /// Allows the use of `#[cfg(sanitize = "option")]`; set when -Zsanitizer is used.
407 (unstable, cfg_sanitize, "1.41.0", Some(39699)),
408 /// Allows `cfg(sanitizer_cfi_generalize_pointers)` and `cfg(sanitizer_cfi_normalize_integers)`.
409 (unstable, cfg_sanitizer_cfi, "1.77.0", Some(89653)),
410 /// Allows `cfg(target(abi = "..."))`.
411 (unstable, cfg_target_compact, "1.63.0", Some(96901)),
412 /// Allows `cfg(target_has_atomic_load_store = "...")`.
413 (unstable, cfg_target_has_atomic, "1.60.0", Some(94039)),
414 /// Allows `cfg(target_has_atomic_equal_alignment = "...")`.
415 (unstable, cfg_target_has_atomic_equal_alignment, "1.60.0", Some(93822)),
416 /// Allows `cfg(target_thread_local)`.
417 (unstable, cfg_target_thread_local, "1.7.0", Some(29594)),
418 /// Allows the use of `#[cfg(ub_checks)` to check if UB checks are enabled.
419 (unstable, cfg_ub_checks, "1.79.0", Some(123499)),
420 /// Allow conditional compilation depending on rust version
421 (unstable, cfg_version, "1.45.0", Some(64796)),
422 /// Allows to use the `#[cfi_encoding = ""]` attribute.
423 (unstable, cfi_encoding, "1.71.0", Some(89653)),
424 /// Allows `for<...>` on closures and coroutines.
425 (unstable, closure_lifetime_binder, "1.64.0", Some(97362)),
426 /// Allows `#[track_caller]` on closures and coroutines.
427 (unstable, closure_track_caller, "1.57.0", Some(87417)),
428 /// Allows `extern "C-cmse-nonsecure-entry" fn()`.
429 (unstable, cmse_nonsecure_entry, "1.48.0", Some(75835)),
430 /// Allows `async {}` expressions in const contexts.
431 (unstable, const_async_blocks, "1.53.0", Some(85368)),
432 /// Allows `const || {}` closures in const contexts.
433 (incomplete, const_closures, "1.68.0", Some(106003)),
434 /// Allows using `~const Destruct` bounds and calling drop impls in const contexts.
435 (unstable, const_destruct, "1.85.0", Some(133214)),
436 /// Allows `for _ in _` loops in const contexts.
437 (unstable, const_for, "1.56.0", Some(87575)),
438 /// Be more precise when looking for live drops in a const context.
439 (unstable, const_precise_live_drops, "1.46.0", Some(73255)),
440 /// Allows `impl const Trait for T` syntax.
441 (unstable, const_trait_impl, "1.42.0", Some(67792)),
442 /// Allows the `?` operator in const contexts.
443 (unstable, const_try, "1.56.0", Some(74935)),
444 /// Allows use of contracts attributes.
445 (incomplete, contracts, "1.86.0", Some(128044)),
446 /// Allows access to internal machinery used to implement contracts.
447 (internal, contracts_internals, "1.86.0", Some(128044)),
448 /// Allows coroutines to be cloned.
449 (unstable, coroutine_clone, "1.65.0", Some(95360)),
450 /// Allows defining coroutines.
451 (unstable, coroutines, "1.21.0", Some(43122)),
452 /// Allows function attribute `#[coverage(on/off)]`, to control coverage
453 /// instrumentation of that function.
454 (unstable, coverage_attribute, "1.74.0", Some(84605)),
455 /// Allows non-builtin attributes in inner attribute position.
456 (unstable, custom_inner_attributes, "1.30.0", Some(54726)),
457 /// Allows custom test frameworks with `#![test_runner]` and `#[test_case]`.
458 (unstable, custom_test_frameworks, "1.30.0", Some(50297)),
459 /// Allows declarative macros 2.0 (`macro`).
460 (unstable, decl_macro, "1.17.0", Some(39412)),
461 /// Allows the use of default values on struct definitions and the construction of struct
462 /// literals with the functional update syntax without a base.
463 (unstable, default_field_values, "1.85.0", Some(132162)),
464 /// Allows using `#[deprecated_safe]` to deprecate the safeness of a function or trait
465 (unstable, deprecated_safe, "1.61.0", Some(94978)),
466 /// Allows having using `suggestion` in the `#[deprecated]` attribute.
467 (unstable, deprecated_suggestion, "1.61.0", Some(94785)),
468 /// Allows deref patterns.
469 (incomplete, deref_patterns, "1.79.0", Some(87121)),
470 /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
471 (unstable, doc_auto_cfg, "1.58.0", Some(43781)),
472 /// Allows `#[doc(cfg(...))]`.
473 (unstable, doc_cfg, "1.21.0", Some(43781)),
474 /// Allows `#[doc(cfg_hide(...))]`.
475 (unstable, doc_cfg_hide, "1.57.0", Some(43781)),
476 /// Allows `#[doc(masked)]`.
477 (unstable, doc_masked, "1.21.0", Some(44027)),
478 /// Allows `dyn* Trait` objects.
479 (incomplete, dyn_star, "1.65.0", Some(102425)),
480 /// Allows the .use postfix syntax `x.use` and use closures `use |x| { ... }`
481 (incomplete, ergonomic_clones, "1.87.0", Some(132290)),
482 /// Allows exhaustive pattern matching on types that contain uninhabited types.
483 (unstable, exhaustive_patterns, "1.13.0", Some(51085)),
484 /// Disallows `extern` without an explicit ABI.
485 (unstable, explicit_extern_abis, "1.88.0", Some(134986)),
486 /// Allows explicit tail calls via `become` expression.
487 (incomplete, explicit_tail_calls, "1.72.0", Some(112788)),
488 /// Allows using `#[export_stable]` which indicates that an item is exportable.
489 (incomplete, export_stable, "1.88.0", Some(139939)),
490 /// Allows using `aapcs`, `efiapi`, `sysv64` and `win64` as calling conventions
491 /// for functions with varargs.
492 (unstable, extended_varargs_abi_support, "1.65.0", Some(100189)),
493 /// Allows using `system` as a calling convention with varargs.
494 (unstable, extern_system_varargs, "1.86.0", Some(136946)),
495 /// Allows defining `extern type`s.
496 (unstable, extern_types, "1.23.0", Some(43467)),
497 /// Allow using 128-bit (quad precision) floating point numbers.
498 (unstable, f128, "1.78.0", Some(116909)),
499 /// Allow using 16-bit (half precision) floating point numbers.
500 (unstable, f16, "1.78.0", Some(116909)),
501 /// Allows the use of `#[ffi_const]` on foreign functions.
502 (unstable, ffi_const, "1.45.0", Some(58328)),
503 /// Allows the use of `#[ffi_pure]` on foreign functions.
504 (unstable, ffi_pure, "1.45.0", Some(58329)),
505 /// Controlling the behavior of fmt::Debug
506 (unstable, fmt_debug, "1.82.0", Some(129709)),
507 /// Allows using `#[repr(align(...))]` on function items
508 (unstable, fn_align, "1.53.0", Some(82232)),
509 /// Support delegating implementation of functions to other already implemented functions.
510 (incomplete, fn_delegation, "1.76.0", Some(118212)),
511 /// Allows impls for the Freeze trait.
512 (internal, freeze_impls, "1.78.0", Some(121675)),
513 /// Frontmatter `---` blocks for use by external tools.
514 (unstable, frontmatter, "1.88.0", Some(136889)),
515 /// Allows defining gen blocks and `gen fn`.
516 (unstable, gen_blocks, "1.75.0", Some(117078)),
517 /// Infer generic args for both consts and types.
518 (unstable, generic_arg_infer, "1.55.0", Some(85077)),
519 /// Allows non-trivial generic constants which have to have wfness manually propagated to callers
520 (incomplete, generic_const_exprs, "1.56.0", Some(76560)),
521 /// Allows generic parameters and where-clauses on free & associated const items.
522 (incomplete, generic_const_items, "1.73.0", Some(113521)),
523 /// Allows the type of const generics to depend on generic parameters
524 (incomplete, generic_const_parameter_types, "1.87.0", Some(137626)),
525 /// Allows any generic constants being used as pattern type range ends
526 (incomplete, generic_pattern_types, "1.86.0", Some(136574)),
527 /// Allows registering static items globally, possibly across crates, to iterate over at runtime.
528 (unstable, global_registration, "1.80.0", Some(125119)),
529 /// Allows using guards in patterns.
530 (incomplete, guard_patterns, "1.85.0", Some(129967)),
531 /// Allows using `..=X` as a patterns in slices.
532 (unstable, half_open_range_patterns_in_slices, "1.66.0", Some(67264)),
533 /// Allows `if let` guard in match arms.
534 (unstable, if_let_guard, "1.47.0", Some(51114)),
535 /// Allows `impl Trait` to be used inside associated types (RFC 2515).
536 (unstable, impl_trait_in_assoc_type, "1.70.0", Some(63063)),
537 /// Allows `impl Trait` in bindings (`let`).
538 (unstable, impl_trait_in_bindings, "1.64.0", Some(63065)),
539 /// Allows `impl Trait` as output type in `Fn` traits in return position of functions.
540 (unstable, impl_trait_in_fn_trait_return, "1.64.0", Some(99697)),
541 /// Allows `use` associated functions from traits.
542 (unstable, import_trait_associated_functions, "1.86.0", Some(134691)),
543 /// Allows associated types in inherent impls.
544 (incomplete, inherent_associated_types, "1.52.0", Some(8995)),
545 /// Allows using `pointer` and `reference` in intra-doc links
546 (unstable, intra_doc_pointers, "1.51.0", Some(80896)),
547 // Allows using the `kl` and `widekl` target features and the associated intrinsics
548 (unstable, keylocker_x86, "1.86.0", Some(134813)),
549 // Allows setting the threshold for the `large_assignments` lint.
550 (unstable, large_assignments, "1.52.0", Some(83518)),
551 /// Allow to have type alias types for inter-crate use.
552 (incomplete, lazy_type_alias, "1.72.0", Some(112792)),
553 /// Allows `if/while p && let q = r && ...` chains.
554 (unstable, let_chains, "1.37.0", Some(53667)),
555 /// Allows using `#[link(kind = "link-arg", name = "...")]`
556 /// to pass custom arguments to the linker.
557 (unstable, link_arg_attribute, "1.76.0", Some(99427)),
558 /// Give access to additional metadata about declarative macro meta-variables.
559 (unstable, macro_metavar_expr, "1.61.0", Some(83527)),
560 /// Provides a way to concatenate identifiers using metavariable expressions.
561 (unstable, macro_metavar_expr_concat, "1.81.0", Some(124225)),
562 /// Allows `#[marker]` on certain traits allowing overlapping implementations.
563 (unstable, marker_trait_attr, "1.30.0", Some(29864)),
564 /// Enables the generic const args MVP (only bare paths, not arbitrary computation).
565 (incomplete, min_generic_const_args, "1.84.0", Some(132980)),
566 /// A minimal, sound subset of specialization intended to be used by the
567 /// standard library until the soundness issues with specialization
568 /// are fixed.
569 (unstable, min_specialization, "1.7.0", Some(31844)),
570 /// Allows qualified paths in struct expressions, struct patterns and tuple struct patterns.
571 (unstable, more_qualified_paths, "1.54.0", Some(86935)),
572 /// Allows the `#[must_not_suspend]` attribute.
573 (unstable, must_not_suspend, "1.57.0", Some(83310)),
574 /// Allows `mut ref` and `mut ref mut` identifier patterns.
575 (incomplete, mut_ref, "1.79.0", Some(123076)),
576 /// Allows using `#[naked]` on `extern "Rust"` functions.
577 (unstable, naked_functions_rustic_abi, "1.88.0", Some(138997)),
578 /// Allows using `#[target_feature(enable = "...")]` on `#[naked]` on functions.
579 (unstable, naked_functions_target_feature, "1.86.0", Some(138568)),
580 /// Allows specifying the as-needed link modifier
581 (unstable, native_link_modifiers_as_needed, "1.53.0", Some(81490)),
582 /// Allow negative trait implementations.
583 (unstable, negative_impls, "1.44.0", Some(68318)),
584 /// Allows the `!` pattern.
585 (incomplete, never_patterns, "1.76.0", Some(118155)),
586 /// Allows the `!` type. Does not imply 'exhaustive_patterns' (below) any more.
587 (unstable, never_type, "1.13.0", Some(35121)),
588 /// Allows diverging expressions to fall back to `!` rather than `()`.
589 (unstable, never_type_fallback, "1.41.0", Some(65992)),
590 /// Switch `..` syntax to use the new (`Copy + IntoIterator`) range types.
591 (unstable, new_range, "1.86.0", Some(123741)),
592 /// Allows `#![no_core]`.
593 (unstable, no_core, "1.3.0", Some(29639)),
594 /// Allows the use of `no_sanitize` attribute.
595 (unstable, no_sanitize, "1.42.0", Some(39699)),
596 /// Allows using the `non_exhaustive_omitted_patterns` lint.
597 (unstable, non_exhaustive_omitted_patterns_lint, "1.57.0", Some(89554)),
598 /// Allows `for<T>` binders in where-clauses
599 (incomplete, non_lifetime_binders, "1.69.0", Some(108185)),
600 /// Allows using enums in offset_of!
601 (unstable, offset_of_enum, "1.75.0", Some(120141)),
602 /// Allows using fields with slice type in offset_of!
603 (unstable, offset_of_slice, "1.81.0", Some(126151)),
604 /// Allows using `#[optimize(X)]`.
605 (unstable, optimize_attribute, "1.34.0", Some(54882)),
606 /// Allows specifying nop padding on functions for dynamic patching.
607 (unstable, patchable_function_entry, "1.81.0", Some(123115)),
608 /// Experimental features that make `Pin` more ergonomic.
609 (incomplete, pin_ergonomics, "1.83.0", Some(130494)),
610 /// Allows postfix match `expr.match { ... }`
611 (unstable, postfix_match, "1.79.0", Some(121618)),
612 /// Allows macro attributes on expressions, statements and non-inline modules.
613 (unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
614 /// Allows the use of raw-dylibs on ELF platforms
615 (incomplete, raw_dylib_elf, "1.87.0", Some(135694)),
616 /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
617 (incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),
618 /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024—structural variant
619 (incomplete, ref_pat_eat_one_layer_2024_structural, "1.81.0", Some(123076)),
620 /// Allows using the `#[register_tool]` attribute.
621 (unstable, register_tool, "1.41.0", Some(66079)),
622 /// Allows the `#[repr(i128)]` attribute for enums.
623 (incomplete, repr128, "1.16.0", Some(56071)),
624 /// Allows `repr(simd)` and importing the various simd intrinsics.
625 (unstable, repr_simd, "1.4.0", Some(27731)),
626 /// Allows bounding the return type of AFIT/RPITIT.
627 (unstable, return_type_notation, "1.70.0", Some(109417)),
628 /// Allows `extern "rust-cold"`.
629 (unstable, rust_cold_cc, "1.63.0", Some(97544)),
630 /// Allows use of x86 SHA512, SM3 and SM4 target-features and intrinsics
631 (unstable, sha512_sm_x86, "1.82.0", Some(126624)),
632 /// Allows the use of SIMD types in functions declared in `extern` blocks.
633 (unstable, simd_ffi, "1.0.0", Some(27731)),
634 /// Allows specialization of implementations (RFC 1210).
635 (incomplete, specialization, "1.7.0", Some(31844)),
636 /// Allows attributes on expressions and non-item statements.
637 (unstable, stmt_expr_attributes, "1.6.0", Some(15701)),
638 /// Allows lints part of the strict provenance effort.
639 (unstable, strict_provenance_lints, "1.61.0", Some(130351)),
640 /// Allows string patterns to dereference values to match them.
641 (unstable, string_deref_patterns, "1.67.0", Some(87121)),
642 /// Allows `super let` statements.
643 (unstable, super_let, "1.88.0", Some(139076)),
644 /// Allows subtrait items to shadow supertrait items.
645 (unstable, supertrait_item_shadowing, "1.86.0", Some(89151)),
646 /// Allows using `#[thread_local]` on `static` items.
647 (unstable, thread_local, "1.0.0", Some(29594)),
648 /// Allows defining `trait X = A + B;` alias items.
649 (unstable, trait_alias, "1.24.0", Some(41517)),
650 /// Allows for transmuting between arrays with sizes that contain generic consts.
651 (unstable, transmute_generic_consts, "1.70.0", Some(109929)),
652 /// Allows #[repr(transparent)] on unions (RFC 2645).
653 (unstable, transparent_unions, "1.37.0", Some(60405)),
654 /// Allows inconsistent bounds in where clauses.
655 (unstable, trivial_bounds, "1.28.0", Some(48214)),
656 /// Allows using `try {...}` expressions.
657 (unstable, try_blocks, "1.29.0", Some(31436)),
658 /// Allows `impl Trait` to be used inside type aliases (RFC 2515).
659 (unstable, type_alias_impl_trait, "1.38.0", Some(63063)),
660 /// Allows creation of instances of a struct by moving fields that have
661 /// not changed from prior instances of the same struct (RFC #2528)
662 (unstable, type_changing_struct_update, "1.58.0", Some(86555)),
663 /// Allows using `unsafe<'a> &'a T` unsafe binder types.
664 (incomplete, unsafe_binders, "1.85.0", Some(130516)),
665 /// Allows declaring fields `unsafe`.
666 (incomplete, unsafe_fields, "1.85.0", Some(132922)),
667 /// Allows const generic parameters to be defined with types that
668 /// are not `Sized`, e.g. `fn foo<const N: [u8]>() {`.
669 (incomplete, unsized_const_params, "1.82.0", Some(95174)),
670 /// Allows unsized fn parameters.
671 (internal, unsized_fn_params, "1.49.0", Some(48055)),
672 /// Allows unsized rvalues at arguments and parameters.
673 (incomplete, unsized_locals, "1.30.0", Some(48055)),
674 /// Allows using the `#[used(linker)]` (or `#[used(compiler)]`) attribute.
675 (unstable, used_with_arg, "1.60.0", Some(93798)),
676 /// Allows use of attributes in `where` clauses.
677 (unstable, where_clause_attrs, "1.87.0", Some(115590)),
678 /// Allows use of x86 `AMX` target-feature attributes and intrinsics
679 (unstable, x86_amx_intrinsics, "1.81.0", Some(126622)),
680 /// Allows use of the `xop` target-feature
681 (unstable, xop_target_feature, "1.81.0", Some(127208)),
682 /// Allows `do yeet` expressions
683 (unstable, yeet_expr, "1.62.0", Some(96373)),
684 (unstable, yield_expr, "1.87.0", Some(43122)),
685 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
686 // Features are listed in alphabetical order. Tidy will fail if you don't keep it this way.
687 // !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!! !!!!
688
689 // -------------------------------------------------------------------------
690 // feature-group-end: actual feature gates
691 // -------------------------------------------------------------------------
692);
693
694impl Features {
695 pub fn dump_feature_usage_metrics(
696 &self,
697 metrics_path: PathBuf,
698 ) -> Result<(), Box<dyn std::error::Error>> {
699 #[derive(serde::Serialize)]
700 struct LibFeature {
701 timestamp: u128,
702 symbol: String,
703 }
704
705 #[derive(serde::Serialize)]
706 struct LangFeature {
707 timestamp: u128,
708 symbol: String,
709 since: Option<String>,
710 }
711
712 #[derive(serde::Serialize)]
713 struct FeatureUsage {
714 lib_features: Vec<LibFeature>,
715 lang_features: Vec<LangFeature>,
716 }
717
718 let metrics_file = std::fs::File::create(metrics_path)?;
719 let metrics_file = std::io::BufWriter::new(metrics_file);
720
721 let now = || {
722 SystemTime::now()
723 .duration_since(UNIX_EPOCH)
724 .expect("system time should always be greater than the unix epoch")
725 .as_nanos()
726 };
727
728 let lib_features = self
729 .enabled_lib_features
730 .iter()
731 .map(|EnabledLibFeature { gate_name, .. }| LibFeature {
732 symbol: gate_name.to_string(),
733 timestamp: now(),
734 })
735 .collect();
736
737 let lang_features = self
738 .enabled_lang_features
739 .iter()
740 .map(|EnabledLangFeature { gate_name, stable_since, .. }| LangFeature {
741 symbol: gate_name.to_string(),
742 since: stable_since.map(|since| since.to_string()),
743 timestamp: now(),
744 })
745 .collect();
746
747 let feature_usage = FeatureUsage { lib_features, lang_features };
748
749 serde_json::to_writer(metrics_file, &feature_usage)?;
750
751 Ok(())
752 }
753}
754
755/// Some features are not allowed to be used together at the same time, if
756/// the two are present, produce an error.
757pub const INCOMPATIBLE_FEATURES: &[(Symbol, Symbol)] = &[
758 // Experimental match ergonomics rulesets are incompatible with each other, to simplify the
759 // boolean logic required to tell which typing rules to use.
760 (sym::ref_pat_eat_one_layer_2024, sym::ref_pat_eat_one_layer_2024_structural),
761];