3 //! This module implements the gating necessary for preventing certain compiler
4 //! features from being used by default. This module will crawl a pre-expanded
5 //! AST to ensure that there are no features which are used that are not
8 //! Features are enabled in programs via the crate-level attributes of
9 //! `#![feature(...)]` with a comma-separated list of features.
11 //! For the purpose of future feature-tracking, once code for detection of feature
12 //! gate usage is added, *do not remove it again* even once the feature
15 use self::AttributeType::*;
16 use self::AttributeGate::*;
18 use rustc_data_structures::fx::FxHashMap;
19 use rustc_target::spec::abi::Abi;
20 use ast::{self, NodeId, PatKind, RangeEnd};
22 use source_map::Spanned;
23 use edition::{ALL_EDITIONS, Edition};
24 use syntax_pos::{Span, DUMMY_SP};
25 use errors::{DiagnosticBuilder, Handler};
26 use visit::{self, FnKind, Visitor};
28 use symbol::{keywords, Symbol};
34 fn f(features: &mut Features, _: Span) {
35 features.$field = true;
37 f as fn(&mut Features, Span)
41 macro_rules! declare_features {
42 ($((active, $feature: ident, $ver: expr, $issue: expr, $edition: expr),)+) => {
43 /// Represents active features that are currently being implemented or
44 /// currently being considered for addition/removal.
45 const ACTIVE_FEATURES:
46 &[(&str, &str, Option<u32>, Option<Edition>, fn(&mut Features, Span))] =
47 &[$((stringify!($feature), $ver, $issue, $edition, set!($feature))),+];
49 /// A set of features to be used by later passes.
52 /// `#![feature]` attrs for language features, for error reporting
53 pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
54 /// `#![feature]` attrs for non-language (library) features
55 pub declared_lib_features: Vec<(Symbol, Span)>,
56 $(pub $feature: bool),+
60 pub fn new() -> Features {
62 declared_lang_features: Vec::new(),
63 declared_lib_features: Vec::new(),
68 pub fn walk_feature_fields<F>(&self, mut f: F)
69 where F: FnMut(&str, bool)
71 $(f(stringify!($feature), self.$feature);)+
76 ($((removed, $feature: ident, $ver: expr, $issue: expr, None, $reason: expr),)+) => {
77 /// Represents unstable features which have since been removed (it was once Active)
78 const REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
79 $((stringify!($feature), $ver, $issue, $reason)),+
83 ($((stable_removed, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
84 /// Represents stable features which have since been removed (it was once Accepted)
85 const STABLE_REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
86 $((stringify!($feature), $ver, $issue, None)),+
90 ($((accepted, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
91 /// Those language feature has since been Accepted (it was once Active)
92 const ACCEPTED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
93 $((stringify!($feature), $ver, $issue, None)),+
98 // If you change this, please modify `src/doc/unstable-book` as well.
100 // Don't ever remove anything from this list; set them to 'Removed'.
102 // The version numbers here correspond to the version in which the current status
103 // was set. This is most important for knowing when a particular feature became
106 // N.B., `tools/tidy/src/features.rs` parses this information directly out of the
107 // source, so take care when modifying it.
110 (active, asm, "1.0.0", Some(29722), None),
111 (active, concat_idents, "1.0.0", Some(29599), None),
112 (active, link_args, "1.0.0", Some(29596), None),
113 (active, log_syntax, "1.0.0", Some(29598), None),
114 (active, non_ascii_idents, "1.0.0", Some(28979), None),
115 (active, plugin_registrar, "1.0.0", Some(29597), None),
116 (active, thread_local, "1.0.0", Some(29594), None),
117 (active, trace_macros, "1.0.0", Some(29598), None),
119 // rustc internal, for now
120 (active, intrinsics, "1.0.0", None, None),
121 (active, lang_items, "1.0.0", None, None),
122 (active, format_args_nl, "1.29.0", None, None),
124 (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
125 (active, linkage, "1.0.0", Some(29603), None),
126 (active, quote, "1.0.0", Some(29601), None),
129 (active, rustc_diagnostic_macros, "1.0.0", None, None),
130 (active, rustc_const_unstable, "1.0.0", None, None),
131 (active, box_syntax, "1.0.0", Some(49733), None),
132 (active, unboxed_closures, "1.0.0", Some(29625), None),
134 (active, fundamental, "1.0.0", Some(29635), None),
135 (active, main, "1.0.0", Some(29634), None),
136 (active, needs_allocator, "1.4.0", Some(27389), None),
137 (active, on_unimplemented, "1.0.0", Some(29628), None),
138 (active, plugin, "1.0.0", Some(29597), None),
139 (active, simd_ffi, "1.0.0", Some(27731), None),
140 (active, start, "1.0.0", Some(29633), None),
141 (active, structural_match, "1.8.0", Some(31434), None),
142 (active, panic_runtime, "1.10.0", Some(32837), None),
143 (active, needs_panic_runtime, "1.10.0", Some(32837), None),
145 // Features specific to OIBIT (auto traits)
146 (active, optin_builtin_traits, "1.0.0", Some(13231), None),
148 // Allows `#[staged_api]`.
151 (active, staged_api, "1.0.0", None, None),
153 // Allows `#![no_core]`.
154 (active, no_core, "1.3.0", Some(29639), None),
156 // Allows the use of `box` in patterns (RFC 469).
157 (active, box_patterns, "1.0.0", Some(29641), None),
159 // Allows the use of the `unsafe_destructor_blind_to_params` attribute (RFC 1238).
160 (active, dropck_parametricity, "1.3.0", Some(28498), None),
162 // Allows using the `may_dangle` attribute (RFC 1327).
163 (active, dropck_eyepatch, "1.10.0", Some(34761), None),
165 // Allows the use of custom attributes (RFC 572).
166 (active, custom_attribute, "1.0.0", Some(29642), None),
168 // Allows the use of `rustc_*` attributes (RFC 572).
169 (active, rustc_attrs, "1.0.0", Some(29642), None),
171 // Allows the use of non lexical lifetimes (RFC 2094).
172 (active, nll, "1.0.0", Some(43234), None),
174 // Allows the use of `#[allow_internal_unstable]`. This is an
175 // attribute on `macro_rules!` and can't use the attribute handling
176 // below (it has to be checked before expansion possibly makes
177 // macros disappear).
180 (active, allow_internal_unstable, "1.0.0", None, None),
182 // Allows the use of `#[allow_internal_unsafe]`. This is an
183 // attribute on `macro_rules!` and can't use the attribute handling
184 // below (it has to be checked before expansion possibly makes
185 // macros disappear).
188 (active, allow_internal_unsafe, "1.0.0", None, None),
190 // Allows the use of slice patterns (issue #23121).
191 (active, slice_patterns, "1.0.0", Some(23121), None),
193 // Allows the definition of `const` functions with some advanced features.
194 (active, const_fn, "1.2.0", Some(24111), None),
196 // Allows let bindings and destructuring in `const` functions and constants.
197 (active, const_let, "1.22.1", Some(48821), None),
199 // Allows accessing fields of unions inside `const` functions.
200 (active, const_fn_union, "1.27.0", Some(51909), None),
202 // Allows casting raw pointers to `usize` during const eval.
203 (active, const_raw_ptr_to_usize_cast, "1.27.0", Some(51910), None),
205 // Allows dereferencing raw pointers during const eval.
206 (active, const_raw_ptr_deref, "1.27.0", Some(51911), None),
208 // Allows reinterpretation of the bits of a value of one type as another type during const eval.
209 (active, const_transmute, "1.29.0", Some(53605), None),
211 // Allows comparing raw pointers during const eval.
212 (active, const_compare_raw_pointers, "1.27.0", Some(53020), None),
214 // Allows panicking during const eval (producing compile-time errors).
215 (active, const_panic, "1.30.0", Some(51999), None),
217 // Allows using `#[prelude_import]` on glob `use` items.
220 (active, prelude_import, "1.2.0", None, None),
222 // Allows default type parameters to influence type inference.
223 (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
225 // Allows associated type defaults.
226 (active, associated_type_defaults, "1.2.0", Some(29661), None),
228 // Allows `repr(simd)` and importing the various simd intrinsics.
229 (active, repr_simd, "1.4.0", Some(27731), None),
231 // Allows `extern "platform-intrinsic" { ... }`.
232 (active, platform_intrinsics, "1.4.0", Some(27731), None),
234 // Allows `#[unwind(..)]`.
236 // rustc internal for rust runtime
237 (active, unwind_attributes, "1.4.0", None, None),
239 // Allows the use of `#[naked]` on functions.
240 (active, naked_functions, "1.9.0", Some(32408), None),
242 // Allows `#[no_debug]`.
243 (active, no_debug, "1.5.0", Some(29721), None),
245 // Allows `#[omit_gdb_pretty_printer_section]`.
248 (active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
250 // Allows `cfg(target_vendor = "...")`.
251 (active, cfg_target_vendor, "1.5.0", Some(29718), None),
253 // Allows attributes on expressions and non-item statements.
254 (active, stmt_expr_attributes, "1.6.0", Some(15701), None),
256 // Allows the use of type ascription in expressions.
257 (active, type_ascription, "1.6.0", Some(23416), None),
259 // Allows `cfg(target_thread_local)`.
260 (active, cfg_target_thread_local, "1.7.0", Some(29594), None),
263 (active, abi_vectorcall, "1.7.0", None, None),
265 // Allows `X..Y` patterns.
266 (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
268 // impl specialization (RFC 1210)
269 (active, specialization, "1.7.0", Some(31844), None),
271 // Allows `cfg(target_has_atomic = "...")`.
272 (active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
274 // The `!` type. Does not imply 'exhaustive_patterns' (below) any more.
275 (active, never_type, "1.13.0", Some(35121), None),
277 // Allows exhaustive pattern matching on types that contain uninhabited types.
278 (active, exhaustive_patterns, "1.13.0", Some(51085), None),
280 // Allows untagged unions `union U { ... }`.
281 (active, untagged_unions, "1.13.0", Some(32836), None),
283 // Used to identify the `compiler_builtins` crate.
286 (active, compiler_builtins, "1.13.0", None, None),
288 // Allows `#[link(..., cfg(..))]`.
289 (active, link_cfg, "1.14.0", Some(37406), None),
291 // Allows `extern "ptx-*" fn()`.
292 (active, abi_ptx, "1.15.0", Some(38788), None),
294 // The `repr(i128)` annotation for enums.
295 (active, repr128, "1.16.0", Some(35118), None),
297 // The `unadjusted` ABI; perma-unstable.
300 (active, abi_unadjusted, "1.16.0", None, None),
302 // Declarative macros 2.0 (`macro`).
303 (active, decl_macro, "1.17.0", Some(39412), None),
305 // Allows `#[link(kind="static-nobundle"...)]`.
306 (active, static_nobundle, "1.16.0", Some(37403), None),
308 // Allows `extern "msp430-interrupt" fn()`.
309 (active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
311 // Used to identify crates that contain sanitizer runtimes.
314 (active, sanitizer_runtime, "1.17.0", None, None),
316 // Used to identify crates that contain the profiler runtime.
319 (active, profiler_runtime, "1.18.0", None, None),
321 // Allows `extern "x86-interrupt" fn()`.
322 (active, abi_x86_interrupt, "1.17.0", Some(40180), None),
324 // Allows the `try {...}` expression.
325 (active, try_blocks, "1.29.0", Some(31436), None),
327 // Allows module-level inline assembly by way of `global_asm!()`.
328 (active, global_asm, "1.18.0", Some(35119), None),
330 // Allows overlapping impls of marker traits.
331 (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
333 // Trait attribute to allow overlapping impls.
334 (active, marker_trait_attr, "1.30.0", Some(29864), None),
337 (active, abi_thiscall, "1.19.0", None, None),
339 // Allows a test to fail without failing the whole suite.
340 (active, allow_fail, "1.19.0", Some(46488), None),
342 // Allows unsized tuple coercion.
343 (active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
346 (active, generators, "1.21.0", Some(43122), None),
349 (active, trait_alias, "1.24.0", Some(41517), None),
352 (active, allocator_internals, "1.20.0", None, None),
354 // `#[doc(cfg(...))]`
355 (active, doc_cfg, "1.21.0", Some(43781), None),
357 (active, doc_masked, "1.21.0", Some(44027), None),
358 // `#[doc(spotlight)]`
359 (active, doc_spotlight, "1.22.0", Some(45040), None),
360 // `#[doc(include = "some-file")]`
361 (active, external_doc, "1.22.0", Some(44732), None),
363 // Future-proofing enums/structs with `#[non_exhaustive]` attribute (RFC 2008).
364 (active, non_exhaustive, "1.22.0", Some(44109), None),
366 // Adds `crate` as visibility modifier, synonymous with `pub(crate)`.
367 (active, crate_visibility_modifier, "1.23.0", Some(53120), None),
370 (active, extern_types, "1.23.0", Some(43467), None),
372 // Allows trait methods with arbitrary self types.
373 (active, arbitrary_self_types, "1.23.0", Some(44874), None),
375 // In-band lifetime bindings (e.g., `fn foo(x: &'a u8) -> &'a u8`).
376 (active, in_band_lifetimes, "1.23.0", Some(44524), None),
378 // Generic associated types (RFC 1598)
379 (active, generic_associated_types, "1.23.0", Some(44265), None),
382 (active, extern_in_paths, "1.23.0", Some(55600), None),
384 // Infer static outlives requirements (RFC 2093).
385 (active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
387 // Multiple patterns with `|` in `if let` and `while let`.
388 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
390 // Allows macro invocations in `extern {}` blocks.
391 (active, macros_in_extern, "1.27.0", Some(49476), None),
393 // `existential type`
394 (active, existential_type, "1.28.0", Some(34511), None),
396 // unstable `#[target_feature]` directives
397 (active, arm_target_feature, "1.27.0", Some(44839), None),
398 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
399 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
400 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
401 (active, mips_target_feature, "1.27.0", Some(44839), None),
402 (active, avx512_target_feature, "1.27.0", Some(44839), None),
403 (active, mmx_target_feature, "1.27.0", Some(44839), None),
404 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
405 (active, tbm_target_feature, "1.27.0", Some(44839), None),
406 (active, wasm_target_feature, "1.30.0", Some(44839), None),
407 (active, adx_target_feature, "1.32.0", Some(44839), None),
408 (active, cmpxchg16b_target_feature, "1.32.0", Some(44839), None),
410 // Allows macro invocations on modules expressions and statements and
411 // procedural macros to expand to non-items.
412 (active, proc_macro_hygiene, "1.30.0", Some(54727), None),
414 // `#[doc(alias = "...")]`
415 (active, doc_alias, "1.27.0", Some(50146), None),
417 // Allows irrefutable patterns in `if let` and `while let` statements (RFC 2086).
418 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
420 // inconsistent bounds in where clauses
421 (active, trivial_bounds, "1.28.0", Some(48214), None),
423 // `'a: { break 'a; }`
424 (active, label_break_value, "1.28.0", Some(48594), None),
426 // Exhaustive pattern matching on `usize` and `isize`.
427 (active, precise_pointer_size_matching, "1.32.0", Some(56354), None),
429 // `#[doc(keyword = "...")]`
430 (active, doc_keyword, "1.28.0", Some(51315), None),
432 // Allows async and await syntax.
433 (active, async_await, "1.28.0", Some(50547), None),
435 // `#[alloc_error_handler]`
436 (active, alloc_error_handler, "1.29.0", Some(51540), None),
438 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
440 // Added for testing E0705; perma-unstable.
441 (active, test_2018_feature, "1.31.0", Some(0), Some(Edition::Edition2018)),
443 // support for arbitrary delimited token streams in non-macro attributes
444 (active, unrestricted_attribute_tokens, "1.30.0", Some(55208), None),
446 // Allows `use x::y;` to resolve through `self::x`, not just `::x`.
447 (active, uniform_paths, "1.30.0", Some(53130), None),
449 // Allows unsized rvalues at arguments and parameters.
450 (active, unsized_locals, "1.30.0", Some(48055), None),
454 (active, custom_test_frameworks, "1.30.0", Some(50297), None),
456 // non-builtin attributes in inner attribute position
457 (active, custom_inner_attributes, "1.30.0", Some(54726), None),
459 // Allow mixing of bind-by-move in patterns and references to
460 // those identifiers in guards, *if* we are using MIR-borrowck
461 // (aka NLL). Essentially this means you need to be using the
462 // 2018 edition or later.
463 (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
465 // Allows `impl Trait` in bindings (`let`, `const`, `static`).
466 (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
468 // `#[cfg_attr(predicate, multiple, attributes, here)]`
469 (active, cfg_attr_multi, "1.31.0", Some(54881), None),
471 // Allows `const _: TYPE = VALUE`.
472 (active, underscore_const_names, "1.31.0", Some(54912), None),
474 // `reason = ` in lint attributes and `expect` lint attribute
475 (active, lint_reasons, "1.31.0", Some(54503), None),
477 // `extern crate self as foo;` puts local crate root into extern prelude under name `foo`.
478 (active, extern_crate_self, "1.31.0", Some(56409), None),
482 (removed, import_shadowing, "1.0.0", None, None, None),
483 (removed, managed_boxes, "1.0.0", None, None, None),
484 // Allows use of unary negate on unsigned integers, e.g., -e for e: u8
485 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
486 (removed, reflect, "1.0.0", Some(27749), None, None),
487 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
488 (removed, opt_out_copy, "1.0.0", None, None, None),
489 (removed, quad_precision_float, "1.0.0", None, None, None),
490 (removed, struct_inherit, "1.0.0", None, None, None),
491 (removed, test_removed_feature, "1.0.0", None, None, None),
492 (removed, visible_private_types, "1.0.0", None, None, None),
493 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
494 // Allows using items which are missing stability attributes
496 (removed, unmarked_api, "1.0.0", None, None, None),
497 (removed, pushpop_unsafe, "1.2.0", None, None, None),
498 (removed, allocator, "1.0.0", None, None, None),
499 (removed, simd, "1.0.0", Some(27731), None,
500 Some("removed in favor of `#[repr(simd)]`")),
501 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
502 Some("merged into `#![feature(slice_patterns)]`")),
503 (removed, macro_reexport, "1.0.0", Some(29638), None,
504 Some("subsumed by `pub use`")),
505 (removed, proc_macro_mod, "1.27.0", Some(54727), None,
506 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
507 (removed, proc_macro_expr, "1.27.0", Some(54727), None,
508 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
509 (removed, proc_macro_non_items, "1.27.0", Some(54727), None,
510 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
511 (removed, proc_macro_gen, "1.27.0", Some(54727), None,
512 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
513 (removed, panic_implementation, "1.28.0", Some(44489), None,
514 Some("subsumed by `#[panic_handler]`")),
515 // Allows the use of `#[derive(Anything)]` as sugar for `#[derive_Anything]`.
516 (removed, custom_derive, "1.0.0", Some(29644), None,
517 Some("subsumed by `#[proc_macro_derive]`")),
521 (stable_removed, no_stack_check, "1.0.0", None, None),
525 (accepted, associated_types, "1.0.0", None, None),
526 // Allows overloading augmented assignment operations like `a += b`.
527 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
528 // Allows empty structs and enum variants with braces.
529 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
530 // Allows indexing into constant arrays.
531 (accepted, const_indexing, "1.26.0", Some(29947), None),
532 (accepted, default_type_params, "1.0.0", None, None),
533 (accepted, globs, "1.0.0", None, None),
534 (accepted, if_let, "1.0.0", None, None),
535 // A temporary feature gate used to enable parser extensions needed
536 // to bootstrap fix for #5723.
537 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
538 (accepted, macro_rules, "1.0.0", None, None),
539 // Allows using `#![no_std]`.
540 (accepted, no_std, "1.6.0", None, None),
541 (accepted, slicing_syntax, "1.0.0", None, None),
542 (accepted, struct_variant, "1.0.0", None, None),
543 // These are used to test this portion of the compiler, they don't actually
545 (accepted, test_accepted_feature, "1.0.0", None, None),
546 (accepted, tuple_indexing, "1.0.0", None, None),
547 // Allows macros to appear in the type position.
548 (accepted, type_macros, "1.13.0", Some(27245), None),
549 (accepted, while_let, "1.0.0", None, None),
550 // Allows `#[deprecated]` attribute.
551 (accepted, deprecated, "1.9.0", Some(29935), None),
553 (accepted, question_mark, "1.13.0", Some(31436), None),
554 // Allows `..` in tuple (struct) patterns.
555 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
556 (accepted, item_like_imports, "1.15.0", Some(35120), None),
557 // Allows using `Self` and associated types in struct expressions and patterns.
558 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
559 // elide `'static` lifetimes in `static`s and `const`s.
560 (accepted, static_in_const, "1.17.0", Some(35897), None),
561 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
562 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
563 // Allows the definition recursive static items.
564 (accepted, static_recursion, "1.17.0", Some(29719), None),
565 // `pub(restricted)` visibilities (RFC 1422)
566 (accepted, pub_restricted, "1.18.0", Some(32409), None),
567 // `#![windows_subsystem]`
568 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
569 // Allows `break {expr}` with a value inside `loop`s.
570 (accepted, loop_break_value, "1.19.0", Some(37339), None),
571 // Permits numeric fields in struct expressions and patterns.
572 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
573 // Coerces non capturing closures to function pointers.
574 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
575 // Allows attributes on struct literal fields.
576 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
577 // Allows the definition of associated constants in `trait` or `impl` blocks.
578 (accepted, associated_consts, "1.20.0", Some(29646), None),
579 // Usage of the `compile_error!` macro.
580 (accepted, compile_error, "1.20.0", Some(40872), None),
581 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
582 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
583 // Allows `Drop` types in constants (RFC 1440).
584 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
585 // Allows the sysV64 ABI to be specified on all platforms
586 // instead of just the platforms on which it is the C ABI.
587 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
588 // Allows `repr(align(16))` struct attribute (RFC 1358).
589 (accepted, repr_align, "1.25.0", Some(33626), None),
590 // Allows '|' at beginning of match arms (RFC 1925).
591 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
592 // Nested groups in `use` (RFC 2128)
593 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
594 // `a..=b` and `..=b`
595 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
596 // Allows `..=` in patterns (RFC 1192).
597 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
598 // Termination trait in main (RFC 1937)
599 (accepted, termination_trait, "1.26.0", Some(43301), None),
600 // `Copy`/`Clone` closures (RFC 2132).
601 (accepted, clone_closures, "1.26.0", Some(44490), None),
602 (accepted, copy_closures, "1.26.0", Some(44490), None),
603 // Allows `impl Trait` in function arguments.
604 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
605 // Allows `impl Trait` in function return types.
606 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
608 (accepted, i128_type, "1.26.0", Some(35118), None),
609 // Default match binding modes (RFC 2005)
610 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
611 // Allows `'_` placeholder lifetimes.
612 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
613 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327).
614 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
615 // Allows `cfg(target_feature = "...")`.
616 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
617 // Allows `#[target_feature(...)]`.
618 (accepted, target_feature, "1.27.0", None, None),
619 // Trait object syntax with `dyn` prefix
620 (accepted, dyn_trait, "1.27.0", Some(44662), None),
621 // Allows `#[must_use]` on functions, and introduces must-use operators (RFC 1940).
622 (accepted, fn_must_use, "1.27.0", Some(43302), None),
623 // Allows use of the `:lifetime` macro fragment specifier.
624 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
625 // Termination trait in tests (RFC 1937)
626 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
627 // The `#[global_allocator]` attribute
628 (accepted, global_allocator, "1.28.0", Some(27389), None),
629 // Allows `#[repr(transparent)]` attribute on newtype structs.
630 (accepted, repr_transparent, "1.28.0", Some(43036), None),
631 // Procedural macros in `proc-macro` crates
632 (accepted, proc_macro, "1.29.0", Some(38356), None),
633 // `foo.rs` as an alternative to `foo/mod.rs`
634 (accepted, non_modrs_mods, "1.30.0", Some(44660), None),
635 // Allows use of the `:vis` macro fragment specifier
636 (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
637 // Allows importing and reexporting macros with `use`,
638 // enables macro modularization in general.
639 (accepted, use_extern_macros, "1.30.0", Some(35896), None),
640 // Allows keywords to be escaped for use as identifiers.
641 (accepted, raw_identifiers, "1.30.0", Some(48589), None),
642 // Attributes scoped to tools.
643 (accepted, tool_attributes, "1.30.0", Some(44690), None),
644 // Allows multi-segment paths in attributes and derives.
645 (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
646 // Allows all literals in attribute lists and values of key-value pairs.
647 (accepted, attr_literals, "1.30.0", Some(34981), None),
648 // Infer outlives requirements (RFC 2093).
649 (accepted, infer_outlives_requirements, "1.30.0", Some(44493), None),
650 (accepted, panic_handler, "1.30.0", Some(44489), None),
651 // Used to preserve symbols (see llvm.used).
652 (accepted, used, "1.30.0", Some(40289), None),
654 (accepted, crate_in_paths, "1.30.0", Some(45477), None),
655 // Resolve absolute paths as paths from other crates.
656 (accepted, extern_absolute_paths, "1.30.0", Some(44660), None),
657 // Access to crate names passed via `--extern` through prelude.
658 (accepted, extern_prelude, "1.30.0", Some(44660), None),
659 // Parentheses in patterns
660 (accepted, pattern_parentheses, "1.31.0", Some(51087), None),
661 // Allows the definition of `const fn` functions.
662 (accepted, min_const_fn, "1.31.0", Some(53555), None),
664 (accepted, tool_lints, "1.31.0", Some(44690), None),
665 // `impl<I:Iterator> Iterator for &mut Iterator`
666 // `impl Debug for Foo<'_>`
667 (accepted, impl_header_lifetime_elision, "1.31.0", Some(15872), None),
668 // `extern crate foo as bar;` puts `bar` into extern prelude.
669 (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
670 // Allows use of the `:literal` macro fragment specifier (RFC 1576).
671 (accepted, macro_literal_matcher, "1.32.0", Some(35625), None),
672 // Use `?` as the Kleene "at most one" operator.
673 (accepted, macro_at_most_once_rep, "1.32.0", Some(48075), None),
674 // `Self` struct constructor (RFC 2302)
675 (accepted, self_struct_ctor, "1.32.0", Some(51994), None),
676 // `Self` in type definitions (RFC 2300)
677 (accepted, self_in_typedefs, "1.32.0", Some(49303), None),
678 // Integer match exhaustiveness checking (RFC 2591)
679 (accepted, exhaustive_integer_patterns, "1.33.0", Some(50907), None),
680 // `use path as _;` and `extern crate c as _;`
681 (accepted, underscore_imports, "1.33.0", Some(48216), None),
682 // Allows `#[repr(packed(N))]` attribute on structs.
683 (accepted, repr_packed, "1.33.0", Some(33158), None),
684 // Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
685 (accepted, min_const_unsafe_fn, "1.33.0", Some(55607), None),
688 // If you change this, please modify `src/doc/unstable-book` as well. You must
689 // move that documentation into the relevant place in the other docs, and
690 // remove the chapter on the flag.
692 #[derive(Copy, Clone, PartialEq, Debug)]
693 pub enum AttributeType {
694 /// Normal, builtin attribute that is consumed
695 /// by the compiler before the unused_attribute check
698 /// Builtin attribute that may not be consumed by the compiler
699 /// before the unused_attribute check. These attributes
700 /// will be ignored by the unused_attribute lint
703 /// Builtin attribute that is only allowed at the crate level
707 pub enum AttributeGate {
708 /// Is gated by a given feature gate, reason
709 /// and function to check if enabled
710 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
712 /// Ungated attribute, can be used on all release channels
717 fn is_deprecated(&self) -> bool {
719 Gated(Stability::Deprecated(_, _), ..) => true,
725 #[derive(Copy, Clone, Debug)]
728 // First argument is tracking issue link; second argument is an optional
729 // help message, which defaults to "remove this attribute"
730 Deprecated(&'static str, Option<&'static str>),
734 impl ::std::fmt::Debug for AttributeGate {
735 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
737 Gated(ref stab, name, expl, _) =>
738 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
739 Ungated => write!(fmt, "Ungated")
744 macro_rules! cfg_fn {
745 ($field: ident) => {{
746 fn f(features: &Features) -> bool {
749 f as fn(&Features) -> bool
753 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
754 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
757 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
758 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
761 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
762 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
765 // Attributes that have a special meaning to rustc or rustdoc
766 pub const BUILTIN_ATTRIBUTES: &[(&str, AttributeType, AttributeGate)] = &[
769 ("warn", Normal, Ungated),
770 ("allow", Normal, Ungated),
771 ("forbid", Normal, Ungated),
772 ("deny", Normal, Ungated),
774 ("macro_use", Normal, Ungated),
775 ("macro_export", Normal, Ungated),
776 ("plugin_registrar", Normal, Ungated),
778 ("cfg", Normal, Ungated),
779 ("cfg_attr", Normal, Ungated),
780 ("main", Normal, Ungated),
781 ("start", Normal, Ungated),
782 ("repr", Normal, Ungated),
783 ("path", Normal, Ungated),
784 ("abi", Normal, Ungated),
785 ("automatically_derived", Normal, Ungated),
786 ("no_mangle", Normal, Ungated),
787 ("no_link", Normal, Ungated),
788 ("derive", Normal, Ungated),
789 ("should_panic", Normal, Ungated),
790 ("ignore", Normal, Ungated),
791 ("no_implicit_prelude", Normal, Ungated),
792 ("reexport_test_harness_main", Normal, Ungated),
793 ("link_args", Normal, Gated(Stability::Unstable,
795 "the `link_args` attribute is experimental and not \
796 portable across platforms, it is recommended to \
797 use `#[link(name = \"foo\")] instead",
798 cfg_fn!(link_args))),
799 ("macro_escape", Normal, Ungated),
802 ("structural_match", Whitelisted, Gated(Stability::Unstable,
804 "the semantics of constant patterns is \
806 cfg_fn!(structural_match))),
809 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
811 "non exhaustive is an experimental feature",
812 cfg_fn!(non_exhaustive))),
815 ("marker", Normal, Gated(Stability::Unstable,
817 "marker traits is an experimental feature",
818 cfg_fn!(marker_trait_attr))),
820 ("plugin", CrateLevel, Gated(Stability::Unstable,
822 "compiler plugins are experimental \
826 ("no_std", CrateLevel, Ungated),
827 ("no_core", CrateLevel, Gated(Stability::Unstable,
829 "no_core is experimental",
831 ("lang", Normal, Gated(Stability::Unstable,
833 "language items are subject to change",
834 cfg_fn!(lang_items))),
835 ("linkage", Whitelisted, Gated(Stability::Unstable,
837 "the `linkage` attribute is experimental \
838 and not portable across platforms",
840 ("thread_local", Whitelisted, Gated(Stability::Unstable,
842 "`#[thread_local]` is an experimental feature, and does \
843 not currently handle destructors.",
844 cfg_fn!(thread_local))),
846 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
848 "the `#[rustc_on_unimplemented]` attribute \
849 is an experimental feature",
850 cfg_fn!(on_unimplemented))),
851 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
852 "rustc_const_unstable",
853 "the `#[rustc_const_unstable]` attribute \
854 is an internal feature",
855 cfg_fn!(rustc_const_unstable))),
856 ("global_allocator", Normal, Ungated),
857 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
858 "allocator_internals",
859 "the `#[default_lib_allocator]` \
860 attribute is an experimental feature",
861 cfg_fn!(allocator_internals))),
862 ("needs_allocator", Normal, Gated(Stability::Unstable,
863 "allocator_internals",
864 "the `#[needs_allocator]` \
865 attribute is an experimental \
867 cfg_fn!(allocator_internals))),
868 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
870 "the `#[panic_runtime]` attribute is \
871 an experimental feature",
872 cfg_fn!(panic_runtime))),
873 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
874 "needs_panic_runtime",
875 "the `#[needs_panic_runtime]` \
876 attribute is an experimental \
878 cfg_fn!(needs_panic_runtime))),
879 ("rustc_outlives", Normal, Gated(Stability::Unstable,
881 "the `#[rustc_outlives]` attribute \
882 is just used for rustc unit tests \
883 and will never be stable",
884 cfg_fn!(rustc_attrs))),
885 ("rustc_variance", Normal, Gated(Stability::Unstable,
887 "the `#[rustc_variance]` attribute \
888 is just used for rustc unit tests \
889 and will never be stable",
890 cfg_fn!(rustc_attrs))),
891 ("rustc_regions", Normal, Gated(Stability::Unstable,
893 "the `#[rustc_regions]` attribute \
894 is just used for rustc unit tests \
895 and will never be stable",
896 cfg_fn!(rustc_attrs))),
897 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
899 "the `#[rustc_error]` attribute \
900 is just used for rustc unit tests \
901 and will never be stable",
902 cfg_fn!(rustc_attrs))),
903 ("rustc_dump_user_substs", Whitelisted, Gated(Stability::Unstable,
906 is just used for rustc unit tests \
907 and will never be stable",
908 cfg_fn!(rustc_attrs))),
909 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
911 "the `#[rustc_if_this_changed]` attribute \
912 is just used for rustc unit tests \
913 and will never be stable",
914 cfg_fn!(rustc_attrs))),
915 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
917 "the `#[rustc_if_this_changed]` attribute \
918 is just used for rustc unit tests \
919 and will never be stable",
920 cfg_fn!(rustc_attrs))),
921 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
923 "the `#[rustc_dirty]` attribute \
924 is just used for rustc unit tests \
925 and will never be stable",
926 cfg_fn!(rustc_attrs))),
927 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
929 "the `#[rustc_clean]` attribute \
930 is just used for rustc unit tests \
931 and will never be stable",
932 cfg_fn!(rustc_attrs))),
933 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
936 is just used for rustc unit tests \
937 and will never be stable",
938 cfg_fn!(rustc_attrs))),
939 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
942 is just used for rustc unit tests \
943 and will never be stable",
944 cfg_fn!(rustc_attrs))),
945 ("rustc_expected_cgu_reuse", Whitelisted, Gated(Stability::Unstable,
948 is just used for rustc unit tests \
949 and will never be stable",
950 cfg_fn!(rustc_attrs))),
951 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
954 is just used for rustc unit tests \
955 and will never be stable",
956 cfg_fn!(rustc_attrs))),
957 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
959 "internal rustc attributes will never be stable",
960 cfg_fn!(rustc_attrs))),
961 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
963 "internal rustc attributes will never be stable",
964 cfg_fn!(rustc_attrs))),
965 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
967 "the `#[rustc_mir]` attribute \
968 is just used for rustc unit tests \
969 and will never be stable",
970 cfg_fn!(rustc_attrs))),
971 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
973 "the `#[rustc_inherit_overflow_checks]` \
974 attribute is just used to control \
975 overflow checking behavior of several \
976 libcore functions that are inlined \
977 across crates and will never be stable",
978 cfg_fn!(rustc_attrs))),
980 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
982 "the `#[rustc_dump_program_clauses]` \
983 attribute is just used for rustc unit \
984 tests and will never be stable",
985 cfg_fn!(rustc_attrs))),
986 ("rustc_test_marker", Normal, Gated(Stability::Unstable,
988 "the `#[rustc_test_marker]` attribute \
989 is used internally to track tests",
990 cfg_fn!(rustc_attrs))),
991 ("rustc_transparent_macro", Whitelisted, Gated(Stability::Unstable,
993 "used internally for testing macro hygiene",
994 cfg_fn!(rustc_attrs))),
997 ("nll", Whitelisted, Gated(Stability::Unstable,
999 "Non lexical lifetimes",
1001 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
1002 "compiler_builtins",
1003 "the `#[compiler_builtins]` attribute is used to \
1004 identify the `compiler_builtins` crate which \
1005 contains compiler-rt intrinsics and will never be \
1007 cfg_fn!(compiler_builtins))),
1008 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
1009 "sanitizer_runtime",
1010 "the `#[sanitizer_runtime]` attribute is used to \
1011 identify crates that contain the runtime of a \
1012 sanitizer and will never be stable",
1013 cfg_fn!(sanitizer_runtime))),
1014 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
1016 "the `#[profiler_runtime]` attribute is used to \
1017 identify the `profiler_builtins` crate which \
1018 contains the profiler runtime and will never be \
1020 cfg_fn!(profiler_runtime))),
1022 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
1023 "allow_internal_unstable",
1024 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
1025 cfg_fn!(allow_internal_unstable))),
1027 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
1028 "allow_internal_unsafe",
1029 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
1030 cfg_fn!(allow_internal_unsafe))),
1032 ("fundamental", Whitelisted, Gated(Stability::Unstable,
1034 "the `#[fundamental]` attribute \
1035 is an experimental feature",
1036 cfg_fn!(fundamental))),
1038 ("proc_macro_derive", Normal, Ungated),
1040 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
1042 "internal implementation detail",
1043 cfg_fn!(rustc_attrs))),
1045 // FIXME: #14408 whitelist docs since rustdoc looks at them
1046 ("doc", Whitelisted, Ungated),
1048 // FIXME: #14406 these are processed in codegen, which happens after the
1050 ("cold", Whitelisted, Ungated),
1051 ("naked", Whitelisted, Gated(Stability::Unstable,
1053 "the `#[naked]` attribute \
1054 is an experimental feature",
1055 cfg_fn!(naked_functions))),
1056 ("target_feature", Whitelisted, Ungated),
1057 ("export_name", Whitelisted, Ungated),
1058 ("inline", Whitelisted, Ungated),
1059 ("link", Whitelisted, Ungated),
1060 ("link_name", Whitelisted, Ungated),
1061 ("link_section", Whitelisted, Ungated),
1062 ("no_builtins", Whitelisted, Ungated),
1063 ("no_mangle", Whitelisted, Ungated),
1064 ("no_debug", Whitelisted, Gated(
1065 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
1067 "the `#[no_debug]` attribute was an experimental feature that has been \
1068 deprecated due to lack of demand",
1069 cfg_fn!(no_debug))),
1070 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
1071 "omit_gdb_pretty_printer_section",
1072 "the `#[omit_gdb_pretty_printer_section]` \
1073 attribute is just used for the Rust test \
1075 cfg_fn!(omit_gdb_pretty_printer_section))),
1076 ("unsafe_destructor_blind_to_params",
1078 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761",
1079 Some("replace this attribute with `#[may_dangle]`")),
1080 "dropck_parametricity",
1081 "unsafe_destructor_blind_to_params has been replaced by \
1082 may_dangle and will be removed in the future",
1083 cfg_fn!(dropck_parametricity))),
1086 Gated(Stability::Unstable,
1088 "may_dangle has unstable semantics and may be removed in the future",
1089 cfg_fn!(dropck_eyepatch))),
1090 ("unwind", Whitelisted, Gated(Stability::Unstable,
1091 "unwind_attributes",
1092 "#[unwind] is experimental",
1093 cfg_fn!(unwind_attributes))),
1094 ("used", Whitelisted, Ungated),
1097 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1099 "`#[prelude_import]` is for use by rustc only",
1100 cfg_fn!(prelude_import))),
1102 // FIXME: #14407 these are only looked at on-demand so we can't
1103 // guarantee they'll have already been checked
1104 ("rustc_deprecated", Whitelisted, Ungated),
1105 ("must_use", Whitelisted, Ungated),
1106 ("stable", Whitelisted, Ungated),
1107 ("unstable", Whitelisted, Ungated),
1108 ("deprecated", Normal, Ungated),
1110 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1112 "unboxed_closures are still evolving",
1113 cfg_fn!(unboxed_closures))),
1115 ("windows_subsystem", Whitelisted, Ungated),
1117 ("proc_macro_attribute", Normal, Ungated),
1118 ("proc_macro", Normal, Ungated),
1120 ("rustc_proc_macro_decls", Normal, Gated(Stability::Unstable,
1121 "rustc_proc_macro_decls",
1122 "used internally by rustc",
1123 cfg_fn!(rustc_attrs))),
1125 ("allow_fail", Normal, Gated(Stability::Unstable,
1127 "allow_fail attribute is currently unstable",
1128 cfg_fn!(allow_fail))),
1130 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1132 "this is an internal attribute that will \
1134 cfg_fn!(rustc_attrs))),
1136 // whitelists "identity-like" conversion methods to suggest on type mismatch
1137 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1139 "this is an internal attribute that will \
1141 cfg_fn!(rustc_attrs))),
1143 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1145 "never will be stable",
1146 cfg_fn!(rustc_attrs))),
1149 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1150 "infer_static_outlives_requirements",
1151 "infer 'static lifetime requirements",
1152 cfg_fn!(infer_static_outlives_requirements))),
1155 ("panic_handler", Normal, Ungated),
1157 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1158 "alloc_error_handler",
1159 "#[alloc_error_handler] is an unstable feature",
1160 cfg_fn!(alloc_error_handler))),
1162 // Crate level attributes
1163 ("crate_name", CrateLevel, Ungated),
1164 ("crate_type", CrateLevel, Ungated),
1165 ("crate_id", CrateLevel, Ungated),
1166 ("feature", CrateLevel, Ungated),
1167 ("no_start", CrateLevel, Ungated),
1168 ("no_main", CrateLevel, Ungated),
1169 ("no_builtins", CrateLevel, Ungated),
1170 ("recursion_limit", CrateLevel, Ungated),
1171 ("type_length_limit", CrateLevel, Ungated),
1172 ("test_runner", CrateLevel, Gated(Stability::Unstable,
1173 "custom_test_frameworks",
1174 EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
1175 cfg_fn!(custom_test_frameworks))),
1178 // cfg(...)'s that are feature gated
1179 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1180 // (name in cfg, feature, function to check if the feature is enabled)
1181 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1182 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1183 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1184 ("rustdoc", "doc_cfg", cfg_fn!(doc_cfg)),
1188 pub struct GatedCfg {
1194 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1195 let name = cfg.name().as_str();
1197 .position(|info| info.0 == name)
1206 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1207 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1208 if !has_feature(features) && !self.span.allows_unstable() {
1209 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1210 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1215 struct Context<'a> {
1216 features: &'a Features,
1217 parse_sess: &'a ParseSess,
1218 plugin_attributes: &'a [(String, AttributeType)],
1221 macro_rules! gate_feature_fn {
1222 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1223 let (cx, has_feature, span,
1224 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1225 let has_feature: bool = has_feature(&$cx.features);
1226 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1227 if !has_feature && !span.allows_unstable() {
1228 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1234 macro_rules! gate_feature {
1235 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1236 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1237 stringify!($feature), $explain, GateStrength::Hard)
1239 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1240 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1241 stringify!($feature), $explain, $level)
1245 impl<'a> Context<'a> {
1246 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1247 debug!("check_attribute(attr = {:?})", attr);
1248 let name = attr.name().as_str();
1249 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1251 if let Gated(_, name, desc, ref has_feature) = *gateage {
1252 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1253 } else if name == "doc" {
1254 if let Some(content) = attr.meta_item_list() {
1255 if content.iter().any(|c| c.check_name("include")) {
1256 gate_feature!(self, external_doc, attr.span,
1257 "#[doc(include = \"...\")] is experimental"
1262 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1266 for &(ref n, ref ty) in self.plugin_attributes {
1267 if attr.path == &**n {
1268 // Plugins can't gate attributes, so we don't check for it
1269 // unlike the code above; we only use this loop to
1270 // short-circuit to avoid the checks below.
1271 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1275 if name.starts_with("rustc_") {
1276 gate_feature!(self, rustc_attrs, attr.span,
1277 "unless otherwise specified, attributes \
1278 with the prefix `rustc_` \
1279 are reserved for internal compiler diagnostics");
1280 } else if !attr::is_known(attr) {
1281 // Only run the custom attribute lint during regular feature gate
1282 // checking. Macro gating runs before the plugin attributes are
1283 // registered, so we skip this in that case.
1285 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1286 may have meaning added to it in the future", attr.path);
1287 gate_feature!(self, custom_attribute, attr.span, &msg);
1293 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1294 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1295 cx.check_attribute(attr, true);
1298 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1299 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1301 // FIXME (#28244): enforce that active features have issue numbers
1302 // assert!(issue.is_some())
1305 // search in Accepted, Removed, or Stable Removed features
1306 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1307 .find(|t| t.0 == feature);
1309 Some(&(_, _, issue, _)) => issue,
1310 None => panic!("Feature `{}` is not declared anywhere", feature),
1315 pub enum GateIssue {
1317 Library(Option<u32>)
1320 #[derive(Debug, Copy, Clone, PartialEq)]
1321 pub enum GateStrength {
1322 /// A hard error. (Most feature gates should use this.)
1324 /// Only a warning. (Use this only as backwards-compatibility demands.)
1328 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1330 feature_err(sess, feature, span, issue, explain).emit();
1333 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1334 explain: &str) -> DiagnosticBuilder<'a> {
1335 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1338 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1339 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1340 let diag = &sess.span_diagnostic;
1342 let issue = match issue {
1343 GateIssue::Language => find_lang_feature_issue(feature),
1344 GateIssue::Library(lib) => lib,
1347 let explanation = match issue {
1348 None | Some(0) => explain.to_owned(),
1349 Some(n) => format!("{} (see issue #{})", explain, n)
1352 let mut err = match level {
1353 GateStrength::Hard => {
1354 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1356 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1359 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1360 if sess.unstable_features.is_nightly_build() {
1361 err.help(&format!("add #![feature({})] to the \
1362 crate attributes to enable",
1366 // If we're on stable and only emitting a "soft" warning, add a note to
1367 // clarify that the feature isn't "on" (rather than being on but
1369 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1370 err.help("a nightly build of the compiler is required to enable this feature");
1377 const EXPLAIN_BOX_SYNTAX: &str =
1378 "box expression syntax is experimental; you can call `Box::new` instead.";
1380 pub const EXPLAIN_STMT_ATTR_SYNTAX: &str =
1381 "attributes on expressions are experimental.";
1383 pub const EXPLAIN_ASM: &str =
1384 "inline assembly is not stable enough for use and is subject to change";
1386 pub const EXPLAIN_GLOBAL_ASM: &str =
1387 "`global_asm!` is not stable enough for use and is subject to change";
1389 pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &str =
1390 "custom test frameworks are an unstable feature";
1392 pub const EXPLAIN_LOG_SYNTAX: &str =
1393 "`log_syntax!` is not stable enough for use and is subject to change";
1395 pub const EXPLAIN_CONCAT_IDENTS: &str =
1396 "`concat_idents` is not stable enough for use and is subject to change";
1398 pub const EXPLAIN_FORMAT_ARGS_NL: &str =
1399 "`format_args_nl` is only for internal language use and is subject to change";
1401 pub const EXPLAIN_TRACE_MACROS: &str =
1402 "`trace_macros` is not stable enough for use and is subject to change";
1403 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &str =
1404 "allow_internal_unstable side-steps feature gating and stability checks";
1405 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &str =
1406 "allow_internal_unsafe side-steps the unsafe_code lint";
1408 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &str =
1409 "unsized tuple coercion is not stable enough for use and is subject to change";
1411 struct PostExpansionVisitor<'a> {
1412 context: &'a Context<'a>,
1415 macro_rules! gate_feature_post {
1416 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1417 let (cx, span) = ($cx, $span);
1418 if !span.allows_unstable() {
1419 gate_feature!(cx.context, $feature, span, $explain)
1422 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1423 let (cx, span) = ($cx, $span);
1424 if !span.allows_unstable() {
1425 gate_feature!(cx.context, $feature, span, $explain, $level)
1430 impl<'a> PostExpansionVisitor<'a> {
1431 fn check_abi(&self, abi: Abi, span: Span) {
1433 Abi::RustIntrinsic => {
1434 gate_feature_post!(&self, intrinsics, span,
1435 "intrinsics are subject to change");
1437 Abi::PlatformIntrinsic => {
1438 gate_feature_post!(&self, platform_intrinsics, span,
1439 "platform intrinsics are experimental and possibly buggy");
1441 Abi::Vectorcall => {
1442 gate_feature_post!(&self, abi_vectorcall, span,
1443 "vectorcall is experimental and subject to change");
1446 gate_feature_post!(&self, abi_thiscall, span,
1447 "thiscall is experimental and subject to change");
1450 gate_feature_post!(&self, unboxed_closures, span,
1451 "rust-call ABI is subject to change");
1454 gate_feature_post!(&self, abi_ptx, span,
1455 "PTX ABIs are experimental and subject to change");
1457 Abi::Unadjusted => {
1458 gate_feature_post!(&self, abi_unadjusted, span,
1459 "unadjusted ABI is an implementation detail and perma-unstable");
1461 Abi::Msp430Interrupt => {
1462 gate_feature_post!(&self, abi_msp430_interrupt, span,
1463 "msp430-interrupt ABI is experimental and subject to change");
1465 Abi::X86Interrupt => {
1466 gate_feature_post!(&self, abi_x86_interrupt, span,
1467 "x86-interrupt ABI is experimental and subject to change");
1469 Abi::AmdGpuKernel => {
1470 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1471 "amdgpu-kernel ABI is experimental and subject to change");
1487 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1488 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1489 if !attr.span.allows_unstable() {
1490 // check for gated attributes
1491 self.context.check_attribute(attr, false);
1494 if attr.check_name("doc") {
1495 if let Some(content) = attr.meta_item_list() {
1496 if content.len() == 1 && content[0].check_name("cfg") {
1497 gate_feature_post!(&self, doc_cfg, attr.span,
1498 "#[doc(cfg(...))] is experimental"
1500 } else if content.iter().any(|c| c.check_name("masked")) {
1501 gate_feature_post!(&self, doc_masked, attr.span,
1502 "#[doc(masked)] is experimental"
1504 } else if content.iter().any(|c| c.check_name("spotlight")) {
1505 gate_feature_post!(&self, doc_spotlight, attr.span,
1506 "#[doc(spotlight)] is experimental"
1508 } else if content.iter().any(|c| c.check_name("alias")) {
1509 gate_feature_post!(&self, doc_alias, attr.span,
1510 "#[doc(alias = \"...\")] is experimental"
1512 } else if content.iter().any(|c| c.check_name("keyword")) {
1513 gate_feature_post!(&self, doc_keyword, attr.span,
1514 "#[doc(keyword = \"...\")] is experimental"
1520 if !self.context.features.unrestricted_attribute_tokens {
1521 // Unfortunately, `parse_meta` cannot be called speculatively
1522 // because it can report errors by itself, so we have to call it
1523 // only if the feature is disabled.
1524 if let Err(mut err) = attr.parse_meta(self.context.parse_sess) {
1525 err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
1530 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1531 if !name.as_str().is_ascii() {
1532 gate_feature_post!(&self,
1534 self.context.parse_sess.source_map().def_span(sp),
1535 "non-ascii idents are not fully supported.");
1539 fn visit_item(&mut self, i: &'a ast::Item) {
1541 ast::ItemKind::Static(..) |
1542 ast::ItemKind::Const(_,_) => {
1543 if i.ident.name == "_" {
1544 gate_feature_post!(&self, underscore_const_names, i.span,
1545 "naming constants with `_` is unstable");
1549 ast::ItemKind::ForeignMod(ref foreign_module) => {
1550 self.check_abi(foreign_module.abi, i.span);
1553 ast::ItemKind::Fn(..) => {
1554 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1555 gate_feature_post!(&self, plugin_registrar, i.span,
1556 "compiler plugins are experimental and possibly buggy");
1558 if attr::contains_name(&i.attrs[..], "start") {
1559 gate_feature_post!(&self, start, i.span,
1560 "a #[start] function is an experimental \
1561 feature whose signature may change \
1564 if attr::contains_name(&i.attrs[..], "main") {
1565 gate_feature_post!(&self, main, i.span,
1566 "declaration of a nonstandard #[main] \
1567 function may change over time, for now \
1568 a top-level `fn main()` is required");
1572 ast::ItemKind::Struct(..) => {
1573 for attr in attr::filter_by_name(&i.attrs[..], "repr") {
1574 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1575 if item.check_name("simd") {
1576 gate_feature_post!(&self, repr_simd, attr.span,
1577 "SIMD types are experimental and possibly buggy");
1583 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1584 if polarity == ast::ImplPolarity::Negative {
1585 gate_feature_post!(&self, optin_builtin_traits,
1587 "negative trait bounds are not yet fully implemented; \
1588 use marker types for now");
1591 if let ast::Defaultness::Default = defaultness {
1592 gate_feature_post!(&self, specialization,
1594 "specialization is unstable");
1598 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1599 gate_feature_post!(&self, optin_builtin_traits,
1601 "auto traits are experimental and possibly buggy");
1604 ast::ItemKind::TraitAlias(..) => {
1609 "trait aliases are experimental"
1613 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1614 let msg = "`macro` is experimental";
1615 gate_feature_post!(&self, decl_macro, i.span, msg);
1618 ast::ItemKind::Existential(..) => {
1623 "existential types are unstable"
1630 visit::walk_item(self, i);
1633 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1635 ast::ForeignItemKind::Fn(..) |
1636 ast::ForeignItemKind::Static(..) => {
1637 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1638 let links_to_llvm = match link_name {
1639 Some(val) => val.as_str().starts_with("llvm."),
1643 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1644 "linking to LLVM intrinsics is experimental");
1647 ast::ForeignItemKind::Ty => {
1648 gate_feature_post!(&self, extern_types, i.span,
1649 "extern types are experimental");
1651 ast::ForeignItemKind::Macro(..) => {}
1654 visit::walk_foreign_item(self, i)
1657 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1659 ast::TyKind::BareFn(ref bare_fn_ty) => {
1660 self.check_abi(bare_fn_ty.abi, ty.span);
1662 ast::TyKind::Never => {
1663 gate_feature_post!(&self, never_type, ty.span,
1664 "The `!` type is experimental");
1668 visit::walk_ty(self, ty)
1671 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1672 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1673 if let ast::TyKind::Never = output_ty.node {
1676 self.visit_ty(output_ty)
1681 fn visit_expr(&mut self, e: &'a ast::Expr) {
1683 ast::ExprKind::Box(_) => {
1684 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1686 ast::ExprKind::Type(..) => {
1687 gate_feature_post!(&self, type_ascription, e.span,
1688 "type ascription is experimental");
1690 ast::ExprKind::ObsoleteInPlace(..) => {
1691 // these get a hard error in ast-validation
1693 ast::ExprKind::Yield(..) => {
1694 gate_feature_post!(&self, generators,
1696 "yield syntax is experimental");
1698 ast::ExprKind::TryBlock(_) => {
1699 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
1701 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1703 gate_feature_post!(&self, if_while_or_patterns, e.span,
1704 "multiple patterns in `if let` and `while let` are unstable");
1707 ast::ExprKind::Block(_, opt_label) => {
1708 if let Some(label) = opt_label {
1709 gate_feature_post!(&self, label_break_value, label.ident.span,
1710 "labels on blocks are unstable");
1713 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1714 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1716 ast::ExprKind::Async(..) => {
1717 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1721 visit::walk_expr(self, e);
1724 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1725 visit::walk_arm(self, arm)
1728 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1729 match pattern.node {
1730 PatKind::Slice(_, Some(ref subslice), _) => {
1731 gate_feature_post!(&self, slice_patterns,
1733 "syntax for subslices in slice patterns is not yet stabilized");
1735 PatKind::Box(..) => {
1736 gate_feature_post!(&self, box_patterns,
1738 "box pattern syntax is experimental");
1740 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1741 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1742 "exclusive range pattern syntax is experimental");
1746 visit::walk_pat(self, pattern)
1749 fn visit_fn(&mut self,
1750 fn_kind: FnKind<'a>,
1751 fn_decl: &'a ast::FnDecl,
1755 FnKind::ItemFn(_, header, _, _) => {
1756 // Check for const fn and async fn declarations.
1757 if header.asyncness.is_async() {
1758 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1760 // Stability of const fn methods are covered in
1761 // `visit_trait_item` and `visit_impl_item` below; this is
1762 // because default methods don't pass through this point.
1764 self.check_abi(header.abi, span);
1766 FnKind::Method(_, sig, _, _) => {
1767 self.check_abi(sig.header.abi, span);
1771 visit::walk_fn(self, fn_kind, fn_decl, span);
1774 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1776 ast::TraitItemKind::Method(ref sig, ref block) => {
1777 if block.is_none() {
1778 self.check_abi(sig.header.abi, ti.span);
1780 if sig.header.constness.node == ast::Constness::Const {
1781 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1784 ast::TraitItemKind::Type(_, ref default) => {
1785 // We use three if statements instead of something like match guards so that all
1786 // of these errors can be emitted if all cases apply.
1787 if default.is_some() {
1788 gate_feature_post!(&self, associated_type_defaults, ti.span,
1789 "associated type defaults are unstable");
1791 if !ti.generics.params.is_empty() {
1792 gate_feature_post!(&self, generic_associated_types, ti.span,
1793 "generic associated types are unstable");
1795 if !ti.generics.where_clause.predicates.is_empty() {
1796 gate_feature_post!(&self, generic_associated_types, ti.span,
1797 "where clauses on associated types are unstable");
1802 visit::walk_trait_item(self, ti);
1805 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1806 if ii.defaultness == ast::Defaultness::Default {
1807 gate_feature_post!(&self, specialization,
1809 "specialization is unstable");
1813 ast::ImplItemKind::Method(..) => {}
1814 ast::ImplItemKind::Existential(..) => {
1819 "existential types are unstable"
1822 ast::ImplItemKind::Type(_) => {
1823 if !ii.generics.params.is_empty() {
1824 gate_feature_post!(&self, generic_associated_types, ii.span,
1825 "generic associated types are unstable");
1827 if !ii.generics.where_clause.predicates.is_empty() {
1828 gate_feature_post!(&self, generic_associated_types, ii.span,
1829 "where clauses on associated types are unstable");
1834 visit::walk_impl_item(self, ii);
1837 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1838 for segment in &path.segments {
1839 // Identifiers we are going to check could come from a legacy macro (e.g., `#[test]`).
1840 // For such macros identifiers must have empty context, because this context is
1841 // used during name resolution and produced names must be unhygienic for compatibility.
1842 // On the other hand, we need the actual non-empty context for feature gate checking
1843 // because it's hygienic even for legacy macros. As previously stated, such context
1844 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1845 // there while keeping location info from the ident span.
1846 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1847 if segment.ident.name == keywords::Extern.name() {
1848 gate_feature_post!(&self, extern_in_paths, span,
1849 "`extern` in paths is experimental");
1853 visit::walk_path(self, path);
1856 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1857 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1858 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1859 "`crate` visibility modifier is experimental");
1861 visit::walk_vis(self, vis);
1865 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1866 crate_edition: Edition) -> Features {
1867 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1868 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1869 if let Some(reason) = reason {
1870 err.span_note(span, reason);
1875 // Some features are known to be incomplete and using them is likely to have
1876 // unanticipated results, such as compiler crashes. We warn the user about these
1878 let incomplete_features = ["generic_associated_types"];
1880 let mut features = Features::new();
1881 let mut edition_enabled_features = FxHashMap::default();
1883 for &edition in ALL_EDITIONS {
1884 if edition <= crate_edition {
1885 // The `crate_edition` implies its respective umbrella feature-gate
1886 // (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
1887 edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
1891 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1892 if let Some(f_edition) = f_edition {
1893 if f_edition <= crate_edition {
1894 set(&mut features, DUMMY_SP);
1895 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1900 // Process the edition umbrella feature-gates first, to ensure
1901 // `edition_enabled_features` is completed before it's queried.
1902 for attr in krate_attrs {
1903 if !attr.check_name("feature") {
1907 let list = match attr.meta_item_list() {
1913 let name = if let Some(word) = mi.word() {
1919 if incomplete_features.iter().any(|f| *f == name.as_str()) {
1920 span_handler.struct_span_warn(
1923 "the feature `{}` is incomplete and may cause the compiler to crash",
1929 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1930 if *edition <= crate_edition {
1934 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1935 if let Some(f_edition) = f_edition {
1936 if f_edition <= *edition {
1937 // FIXME(Manishearth) there is currently no way to set
1938 // lib features by edition
1939 set(&mut features, DUMMY_SP);
1940 edition_enabled_features.insert(Symbol::intern(name), *edition);
1948 for attr in krate_attrs {
1949 if !attr.check_name("feature") {
1953 let list = match attr.meta_item_list() {
1956 span_err!(span_handler, attr.span, E0555,
1957 "malformed feature attribute, expected #![feature(...)]");
1963 let name = if let Some(word) = mi.word() {
1966 span_err!(span_handler, mi.span, E0556,
1967 "malformed feature, expected just one word");
1971 if let Some(edition) = edition_enabled_features.get(&name) {
1976 "the feature `{}` is included in the Rust {} edition",
1983 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
1984 // Handled in the separate loop above.
1988 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
1989 set(&mut features, mi.span);
1990 features.declared_lang_features.push((name, mi.span, None));
1994 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
1995 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
1996 if let Some((.., reason)) = removed.or(stable_removed) {
1997 feature_removed(span_handler, mi.span, *reason);
2001 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
2002 let since = Some(Symbol::intern(since));
2003 features.declared_lang_features.push((name, mi.span, since));
2007 features.declared_lib_features.push((name, mi.span));
2014 pub fn check_crate(krate: &ast::Crate,
2016 features: &Features,
2017 plugin_attributes: &[(String, AttributeType)],
2018 unstable: UnstableFeatures) {
2019 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2026 let visitor = &mut PostExpansionVisitor { context: &ctx };
2027 visit::walk_crate(visitor, krate);
2030 #[derive(Clone, Copy, Hash)]
2031 pub enum UnstableFeatures {
2032 /// Hard errors for unstable features are active, as on
2033 /// beta/stable channels.
2035 /// Allow features to be activated, as on nightly.
2037 /// Errors are bypassed for bootstrapping. This is required any time
2038 /// during the build that feature-related lints are set to warn or above
2039 /// because the build turns on warnings-as-errors and uses lots of unstable
2040 /// features. As a result, this is always required for building Rust itself.
2044 impl UnstableFeatures {
2045 pub fn from_environment() -> UnstableFeatures {
2046 // Whether this is a feature-staged build, i.e., on the beta or stable channel
2047 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2048 // Whether we should enable unstable features for bootstrapping
2049 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2050 match (disable_unstable_features, bootstrap) {
2051 (_, true) => UnstableFeatures::Cheat,
2052 (true, _) => UnstableFeatures::Disallow,
2053 (false, _) => UnstableFeatures::Allow
2057 pub fn is_nightly_build(&self) -> bool {
2059 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2065 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2066 unstable: UnstableFeatures) {
2067 let allow_features = match unstable {
2068 UnstableFeatures::Allow => true,
2069 UnstableFeatures::Disallow => false,
2070 UnstableFeatures::Cheat => true
2072 if !allow_features {
2073 for attr in &krate.attrs {
2074 if attr.check_name("feature") {
2075 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2076 span_err!(span_handler, attr.span, E0554,
2077 "#![feature] may not be used on the {} release channel",