1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 //! This module implements the gating necessary for preventing certain compiler
14 //! features from being used by default. This module will crawl a pre-expanded
15 //! AST to ensure that there are no features which are used that are not
18 //! Features are enabled in programs via the crate-level attributes of
19 //! `#![feature(...)]` with a comma-separated list of features.
21 //! For the purpose of future feature-tracking, once code for detection of feature
22 //! gate usage is added, *do not remove it again* even once the feature
25 use self::AttributeType::*;
26 use self::AttributeGate::*;
28 use rustc_data_structures::fx::FxHashMap;
29 use rustc_target::spec::abi::Abi;
30 use ast::{self, NodeId, PatKind, RangeEnd};
32 use source_map::Spanned;
33 use edition::{ALL_EDITIONS, Edition};
34 use syntax_pos::{Span, DUMMY_SP};
35 use errors::{DiagnosticBuilder, Handler};
36 use visit::{self, FnKind, Visitor};
38 use symbol::{keywords, Symbol};
44 fn f(features: &mut Features, _: Span) {
45 features.$field = true;
47 f as fn(&mut Features, Span)
51 macro_rules! declare_features {
52 ($((active, $feature: ident, $ver: expr, $issue: expr, $edition: expr),)+) => {
53 /// Represents active features that are currently being implemented or
54 /// currently being considered for addition/removal.
55 const ACTIVE_FEATURES:
56 &'static [(&'static str, &'static str, Option<u32>,
57 Option<Edition>, fn(&mut Features, Span))] =
58 &[$((stringify!($feature), $ver, $issue, $edition, set!($feature))),+];
60 /// A set of features to be used by later passes.
63 /// `#![feature]` attrs for language features, for error reporting
64 pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
65 /// `#![feature]` attrs for non-language (library) features
66 pub declared_lib_features: Vec<(Symbol, Span)>,
67 $(pub $feature: bool),+
71 pub fn new() -> Features {
73 declared_lang_features: Vec::new(),
74 declared_lib_features: Vec::new(),
79 pub fn walk_feature_fields<F>(&self, mut f: F)
80 where F: FnMut(&str, bool)
82 $(f(stringify!($feature), self.$feature);)+
87 ($((removed, $feature: ident, $ver: expr, $issue: expr, None, $reason: expr),)+) => {
88 /// Represents unstable features which have since been removed (it was once Active)
89 const REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
90 $((stringify!($feature), $ver, $issue, $reason)),+
94 ($((stable_removed, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
95 /// Represents stable features which have since been removed (it was once Accepted)
96 const STABLE_REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
97 $((stringify!($feature), $ver, $issue, None)),+
101 ($((accepted, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
102 /// Those language feature has since been Accepted (it was once Active)
103 const ACCEPTED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
104 $((stringify!($feature), $ver, $issue, None)),+
109 // If you change this, please modify src/doc/unstable-book as well.
111 // Don't ever remove anything from this list; set them to 'Removed'.
113 // The version numbers here correspond to the version in which the current status
114 // was set. This is most important for knowing when a particular feature became
117 // NB: tools/tidy/src/features.rs parses this information directly out of the
118 // source, so take care when modifying it.
121 (active, asm, "1.0.0", Some(29722), None),
122 (active, concat_idents, "1.0.0", Some(29599), None),
123 (active, link_args, "1.0.0", Some(29596), None),
124 (active, log_syntax, "1.0.0", Some(29598), None),
125 (active, non_ascii_idents, "1.0.0", Some(28979), None),
126 (active, plugin_registrar, "1.0.0", Some(29597), None),
127 (active, thread_local, "1.0.0", Some(29594), None),
128 (active, trace_macros, "1.0.0", Some(29598), None),
130 // rustc internal, for now
131 (active, intrinsics, "1.0.0", None, None),
132 (active, lang_items, "1.0.0", None, None),
133 (active, format_args_nl, "1.29.0", None, None),
135 (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
136 (active, linkage, "1.0.0", Some(29603), None),
137 (active, quote, "1.0.0", Some(29601), None),
140 (active, rustc_diagnostic_macros, "1.0.0", None, None),
141 (active, rustc_const_unstable, "1.0.0", None, None),
142 (active, box_syntax, "1.0.0", Some(49733), None),
143 (active, unboxed_closures, "1.0.0", Some(29625), None),
145 (active, fundamental, "1.0.0", Some(29635), None),
146 (active, main, "1.0.0", Some(29634), None),
147 (active, needs_allocator, "1.4.0", Some(27389), None),
148 (active, on_unimplemented, "1.0.0", Some(29628), None),
149 (active, plugin, "1.0.0", Some(29597), None),
150 (active, simd_ffi, "1.0.0", Some(27731), None),
151 (active, start, "1.0.0", Some(29633), None),
152 (active, structural_match, "1.8.0", Some(31434), None),
153 (active, panic_runtime, "1.10.0", Some(32837), None),
154 (active, needs_panic_runtime, "1.10.0", Some(32837), None),
156 // OIBIT specific features
157 (active, optin_builtin_traits, "1.0.0", Some(13231), None),
159 // Allows use of #[staged_api]
162 (active, staged_api, "1.0.0", None, None),
164 // Allows using #![no_core]
165 (active, no_core, "1.3.0", Some(29639), None),
167 // Allows using `box` in patterns; RFC 469
168 (active, box_patterns, "1.0.0", Some(29641), None),
170 // Allows using the unsafe_destructor_blind_to_params attribute;
172 (active, dropck_parametricity, "1.3.0", Some(28498), None),
174 // Allows using the may_dangle attribute; RFC 1327
175 (active, dropck_eyepatch, "1.10.0", Some(34761), None),
177 // Allows the use of custom attributes; RFC 572
178 (active, custom_attribute, "1.0.0", Some(29642), None),
180 // Allows the use of #[derive(Anything)] as sugar for
181 // #[derive_Anything].
182 (active, custom_derive, "1.0.0", Some(29644), None),
184 // Allows the use of rustc_* attributes; RFC 572
185 (active, rustc_attrs, "1.0.0", Some(29642), None),
187 // Allows the use of non lexical lifetimes; RFC 2094
188 (active, nll, "1.0.0", Some(43234), None),
190 // Allows the use of #[allow_internal_unstable]. This is an
191 // attribute on macro_rules! and can't use the attribute handling
192 // below (it has to be checked before expansion possibly makes
193 // macros disappear).
196 (active, allow_internal_unstable, "1.0.0", None, None),
198 // Allows the use of #[allow_internal_unsafe]. This is an
199 // attribute on macro_rules! and can't use the attribute handling
200 // below (it has to be checked before expansion possibly makes
201 // macros disappear).
204 (active, allow_internal_unsafe, "1.0.0", None, None),
206 // #23121. Array patterns have some hazards yet.
207 (active, slice_patterns, "1.0.0", Some(23121), None),
209 // Allows the definition of `const fn` functions with some advanced features.
210 (active, const_fn, "1.2.0", Some(24111), None),
212 // Allows let bindings and destructuring in `const fn` functions and constants.
213 (active, const_let, "1.22.1", Some(48821), None),
215 // Allows accessing fields of unions inside const fn.
216 (active, const_fn_union, "1.27.0", Some(51909), None),
218 // Allows casting raw pointers to `usize` during const eval.
219 (active, const_raw_ptr_to_usize_cast, "1.27.0", Some(51910), None),
221 // Allows dereferencing raw pointers during const eval.
222 (active, const_raw_ptr_deref, "1.27.0", Some(51911), None),
224 // Allows reinterpretation of the bits of a value of one type as another type during const eval.
225 (active, const_transmute, "1.29.0", Some(53605), None),
227 // Allows comparing raw pointers during const eval.
228 (active, const_compare_raw_pointers, "1.27.0", Some(53020), None),
230 // Allows panicking during const eval (produces compile-time errors)
231 (active, const_panic, "1.30.0", Some(51999), None),
233 // Allows using #[prelude_import] on glob `use` items.
236 (active, prelude_import, "1.2.0", None, None),
238 // Allows default type parameters to influence type inference.
239 (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
241 // Allows associated type defaults
242 (active, associated_type_defaults, "1.2.0", Some(29661), None),
244 // Allows `repr(simd)`, and importing the various simd intrinsics
245 (active, repr_simd, "1.4.0", Some(27731), None),
247 // Allows `extern "platform-intrinsic" { ... }`
248 (active, platform_intrinsics, "1.4.0", Some(27731), None),
250 // Allows `#[unwind(..)]`
251 // rustc internal for rust runtime
252 (active, unwind_attributes, "1.4.0", None, None),
254 // Allows the use of `#[naked]` on functions.
255 (active, naked_functions, "1.9.0", Some(32408), None),
257 // Allows `#[no_debug]`
258 (active, no_debug, "1.5.0", Some(29721), None),
260 // Allows `#[omit_gdb_pretty_printer_section]`
263 (active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
265 // Allows cfg(target_vendor = "...").
266 (active, cfg_target_vendor, "1.5.0", Some(29718), None),
268 // Allow attributes on expressions and non-item statements
269 (active, stmt_expr_attributes, "1.6.0", Some(15701), None),
271 // allow using type ascription in expressions
272 (active, type_ascription, "1.6.0", Some(23416), None),
274 // Allows cfg(target_thread_local)
275 (active, cfg_target_thread_local, "1.7.0", Some(29594), None),
278 (active, abi_vectorcall, "1.7.0", None, None),
281 (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
283 // impl specialization (RFC 1210)
284 (active, specialization, "1.7.0", Some(31844), None),
286 // Allows cfg(target_has_atomic = "...").
287 (active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
289 // The `!` type. Does not imply exhaustive_patterns (below) any more.
290 (active, never_type, "1.13.0", Some(35121), None),
292 // Allows exhaustive pattern matching on types that contain uninhabited types
293 (active, exhaustive_patterns, "1.13.0", Some(51085), None),
295 // Allows untagged unions `union U { ... }`
296 (active, untagged_unions, "1.13.0", Some(32836), None),
298 // Used to identify the `compiler_builtins` crate
300 (active, compiler_builtins, "1.13.0", None, None),
302 // Allows #[link(..., cfg(..))]
303 (active, link_cfg, "1.14.0", Some(37406), None),
305 // `extern "ptx-*" fn()`
306 (active, abi_ptx, "1.15.0", Some(38788), None),
308 // The `repr(i128)` annotation for enums
309 (active, repr128, "1.16.0", Some(35118), None),
311 // The `unadjusted` ABI. Perma unstable.
313 (active, abi_unadjusted, "1.16.0", None, None),
315 // Declarative macros 2.0 (`macro`).
316 (active, decl_macro, "1.17.0", Some(39412), None),
318 // Allows #[link(kind="static-nobundle"...)]
319 (active, static_nobundle, "1.16.0", Some(37403), None),
321 // `extern "msp430-interrupt" fn()`
322 (active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
324 // Used to identify crates that contain sanitizer runtimes
326 (active, sanitizer_runtime, "1.17.0", None, None),
328 // Used to identify crates that contain the profiler runtime
331 (active, profiler_runtime, "1.18.0", None, None),
333 // `extern "x86-interrupt" fn()`
334 (active, abi_x86_interrupt, "1.17.0", Some(40180), None),
336 // Allows the `try {...}` expression
337 (active, try_blocks, "1.29.0", Some(31436), None),
339 // Allows module-level inline assembly by way of global_asm!()
340 (active, global_asm, "1.18.0", Some(35119), None),
342 // Allows overlapping impls of marker traits
343 (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
345 // Trait attribute to allow overlapping impls
346 (active, marker_trait_attr, "1.30.0", Some(29864), None),
349 (active, abi_thiscall, "1.19.0", None, None),
351 // Allows a test to fail without failing the whole suite
352 (active, allow_fail, "1.19.0", Some(46488), None),
354 // Allows unsized tuple coercion.
355 (active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
358 (active, generators, "1.21.0", Some(43122), None),
361 (active, trait_alias, "1.24.0", Some(41517), None),
364 (active, allocator_internals, "1.20.0", None, None),
367 (active, doc_cfg, "1.21.0", Some(43781), None),
369 (active, doc_masked, "1.21.0", Some(44027), None),
371 (active, doc_spotlight, "1.22.0", Some(45040), None),
372 // #[doc(include="some-file")]
373 (active, external_doc, "1.22.0", Some(44732), None),
375 // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
376 (active, non_exhaustive, "1.22.0", Some(44109), None),
378 // `crate` as visibility modifier, synonymous to `pub(crate)`
379 (active, crate_visibility_modifier, "1.23.0", Some(53120), None),
382 (active, extern_types, "1.23.0", Some(43467), None),
384 // Allows trait methods with arbitrary self types
385 (active, arbitrary_self_types, "1.23.0", Some(44874), None),
387 // In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
388 (active, in_band_lifetimes, "1.23.0", Some(44524), None),
390 // Generic associated types (RFC 1598)
391 (active, generic_associated_types, "1.23.0", Some(44265), None),
394 (active, extern_in_paths, "1.23.0", Some(55600), None),
396 // Infer static outlives requirements; RFC 2093
397 (active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
399 // Multiple patterns with `|` in `if let` and `while let`
400 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
402 // Allows `#[repr(packed)]` attribute on structs
403 (active, repr_packed, "1.26.0", Some(33158), None),
405 // `use path as _;` and `extern crate c as _;`
406 (active, underscore_imports, "1.26.0", Some(48216), None),
408 // Allows macro invocations in `extern {}` blocks
409 (active, macros_in_extern, "1.27.0", Some(49476), None),
411 // `existential type`
412 (active, existential_type, "1.28.0", Some(34511), None),
414 // unstable #[target_feature] directives
415 (active, arm_target_feature, "1.27.0", Some(44839), None),
416 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
417 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
418 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
419 (active, mips_target_feature, "1.27.0", Some(44839), None),
420 (active, avx512_target_feature, "1.27.0", Some(44839), None),
421 (active, mmx_target_feature, "1.27.0", Some(44839), None),
422 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
423 (active, tbm_target_feature, "1.27.0", Some(44839), None),
424 (active, wasm_target_feature, "1.30.0", Some(44839), None),
426 // Allows macro invocations on modules expressions and statements and
427 // procedural macros to expand to non-items.
428 (active, proc_macro_hygiene, "1.30.0", Some(54727), None),
430 // #[doc(alias = "...")]
431 (active, doc_alias, "1.27.0", Some(50146), None),
433 // Allows irrefutable patterns in if-let and while-let statements (RFC 2086)
434 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
436 // inconsistent bounds in where clauses
437 (active, trivial_bounds, "1.28.0", Some(48214), None),
440 (active, label_break_value, "1.28.0", Some(48594), None),
442 // Integer match exhaustiveness checking
443 (active, exhaustive_integer_patterns, "1.30.0", Some(50907), None),
445 // #[doc(keyword = "...")]
446 (active, doc_keyword, "1.28.0", Some(51315), None),
448 // Allows async and await syntax
449 (active, async_await, "1.28.0", Some(50547), None),
451 // #[alloc_error_handler]
452 (active, alloc_error_handler, "1.29.0", Some(51540), None),
454 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
456 // Perma-unstable; added for testing E0705
457 (active, test_2018_feature, "1.31.0", Some(0), Some(Edition::Edition2018)),
459 // Support for arbitrary delimited token streams in non-macro attributes
460 (active, unrestricted_attribute_tokens, "1.30.0", Some(55208), None),
462 // Allows `use x::y;` to resolve through `self::x`, not just `::x`
463 (active, uniform_paths, "1.30.0", Some(53130), None),
465 // Allows unsized rvalues at arguments and parameters
466 (active, unsized_locals, "1.30.0", Some(48055), None),
470 (active, custom_test_frameworks, "1.30.0", Some(50297), None),
472 // Non-builtin attributes in inner attribute position
473 (active, custom_inner_attributes, "1.30.0", Some(54726), None),
475 // allow mixing of bind-by-move in patterns and references to
476 // those identifiers in guards, *if* we are using MIR-borrowck
477 // (aka NLL). Essentially this means you need to be on
478 // edition:2018 or later.
479 (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
481 // Allows `impl Trait` in bindings (`let`, `const`, `static`)
482 (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
484 // #[cfg_attr(predicate, multiple, attributes, here)]
485 (active, cfg_attr_multi, "1.31.0", Some(54881), None),
487 // Allows `const _: TYPE = VALUE`
488 (active, underscore_const_names, "1.31.0", Some(54912), None),
490 // `reason = ` in lint attributes and `expect` lint attribute
491 (active, lint_reasons, "1.31.0", Some(54503), None),
493 // `extern crate self as foo;` puts local crate root into extern prelude under name `foo`.
494 (active, extern_crate_self, "1.31.0", Some(54658), None),
498 (removed, import_shadowing, "1.0.0", None, None, None),
499 (removed, managed_boxes, "1.0.0", None, None, None),
500 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
501 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
502 (removed, reflect, "1.0.0", Some(27749), None, None),
503 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
504 (removed, opt_out_copy, "1.0.0", None, None, None),
505 (removed, quad_precision_float, "1.0.0", None, None, None),
506 (removed, struct_inherit, "1.0.0", None, None, None),
507 (removed, test_removed_feature, "1.0.0", None, None, None),
508 (removed, visible_private_types, "1.0.0", None, None, None),
509 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
510 // Allows using items which are missing stability attributes
512 (removed, unmarked_api, "1.0.0", None, None, None),
513 (removed, pushpop_unsafe, "1.2.0", None, None, None),
514 (removed, allocator, "1.0.0", None, None, None),
515 (removed, simd, "1.0.0", Some(27731), None,
516 Some("removed in favor of `#[repr(simd)]`")),
517 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
518 Some("merged into `#![feature(slice_patterns)]`")),
519 (removed, macro_reexport, "1.0.0", Some(29638), None,
520 Some("subsumed by `pub use`")),
521 (removed, proc_macro_mod, "1.27.0", Some(54727), None,
522 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
523 (removed, proc_macro_expr, "1.27.0", Some(54727), None,
524 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
525 (removed, proc_macro_non_items, "1.27.0", Some(54727), None,
526 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
527 (removed, proc_macro_gen, "1.27.0", Some(54727), None,
528 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
529 (removed, panic_implementation, "1.28.0", Some(44489), None,
530 Some("subsumed by `#[panic_handler]`")),
534 (stable_removed, no_stack_check, "1.0.0", None, None),
538 (accepted, associated_types, "1.0.0", None, None),
539 // allow overloading augmented assignment operations like `a += b`
540 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
541 // allow empty structs and enum variants with braces
542 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
543 // Allows indexing into constant arrays.
544 (accepted, const_indexing, "1.26.0", Some(29947), None),
545 (accepted, default_type_params, "1.0.0", None, None),
546 (accepted, globs, "1.0.0", None, None),
547 (accepted, if_let, "1.0.0", None, None),
548 // A temporary feature gate used to enable parser extensions needed
549 // to bootstrap fix for #5723.
550 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
551 (accepted, macro_rules, "1.0.0", None, None),
552 // Allows using #![no_std]
553 (accepted, no_std, "1.6.0", None, None),
554 (accepted, slicing_syntax, "1.0.0", None, None),
555 (accepted, struct_variant, "1.0.0", None, None),
556 // These are used to test this portion of the compiler, they don't actually
558 (accepted, test_accepted_feature, "1.0.0", None, None),
559 (accepted, tuple_indexing, "1.0.0", None, None),
560 // Allows macros to appear in the type position.
561 (accepted, type_macros, "1.13.0", Some(27245), None),
562 (accepted, while_let, "1.0.0", None, None),
563 // Allows `#[deprecated]` attribute
564 (accepted, deprecated, "1.9.0", Some(29935), None),
566 (accepted, question_mark, "1.13.0", Some(31436), None),
567 // Allows `..` in tuple (struct) patterns
568 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
569 (accepted, item_like_imports, "1.15.0", Some(35120), None),
570 // Allows using `Self` and associated types in struct expressions and patterns.
571 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
572 // elide `'static` lifetimes in `static`s and `const`s
573 (accepted, static_in_const, "1.17.0", Some(35897), None),
574 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
575 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
576 // Allows the definition recursive static items.
577 (accepted, static_recursion, "1.17.0", Some(29719), None),
578 // pub(restricted) visibilities (RFC 1422)
579 (accepted, pub_restricted, "1.18.0", Some(32409), None),
580 // The #![windows_subsystem] attribute
581 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
582 // Allows `break {expr}` with a value inside `loop`s.
583 (accepted, loop_break_value, "1.19.0", Some(37339), None),
584 // Permits numeric fields in struct expressions and patterns.
585 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
586 // Coerces non capturing closures to function pointers
587 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
588 // Allows attributes on struct literal fields.
589 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
590 // Allows the definition of associated constants in `trait` or `impl`
592 (accepted, associated_consts, "1.20.0", Some(29646), None),
593 // Usage of the `compile_error!` macro
594 (accepted, compile_error, "1.20.0", Some(40872), None),
595 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
596 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
597 // Allow Drop types in constants (RFC 1440)
598 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
599 // Allows the sysV64 ABI to be specified on all platforms
600 // instead of just the platforms on which it is the C ABI
601 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
602 // Allows `repr(align(16))` struct attribute (RFC 1358)
603 (accepted, repr_align, "1.25.0", Some(33626), None),
604 // allow '|' at beginning of match arms (RFC 1925)
605 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
606 // Nested groups in `use` (RFC 2128)
607 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
609 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
610 // allow `..=` in patterns (RFC 1192)
611 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
612 // Termination trait in main (RFC 1937)
613 (accepted, termination_trait, "1.26.0", Some(43301), None),
614 // Copy/Clone closures (RFC 2132)
615 (accepted, clone_closures, "1.26.0", Some(44490), None),
616 (accepted, copy_closures, "1.26.0", Some(44490), None),
617 // Allows `impl Trait` in function arguments.
618 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
619 // Allows `impl Trait` in function return types.
620 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
622 (accepted, i128_type, "1.26.0", Some(35118), None),
623 // Default match binding modes (RFC 2005)
624 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
625 // allow `'_` placeholder lifetimes
626 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
627 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
628 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
629 // Allows cfg(target_feature = "...").
630 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
631 // Allows #[target_feature(...)]
632 (accepted, target_feature, "1.27.0", None, None),
633 // Trait object syntax with `dyn` prefix
634 (accepted, dyn_trait, "1.27.0", Some(44662), None),
635 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
636 (accepted, fn_must_use, "1.27.0", Some(43302), None),
637 // Allows use of the :lifetime macro fragment specifier
638 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
639 // Termination trait in tests (RFC 1937)
640 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
641 // The #[global_allocator] attribute
642 (accepted, global_allocator, "1.28.0", Some(27389), None),
643 // Allows `#[repr(transparent)]` attribute on newtype structs
644 (accepted, repr_transparent, "1.28.0", Some(43036), None),
645 // Defining procedural macros in `proc-macro` crates
646 (accepted, proc_macro, "1.29.0", Some(38356), None),
647 // `foo.rs` as an alternative to `foo/mod.rs`
648 (accepted, non_modrs_mods, "1.30.0", Some(44660), None),
649 // Allows use of the :vis macro fragment specifier
650 (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
651 // Allows importing and reexporting macros with `use`,
652 // enables macro modularization in general.
653 (accepted, use_extern_macros, "1.30.0", Some(35896), None),
654 // Allows keywords to be escaped for use as identifiers
655 (accepted, raw_identifiers, "1.30.0", Some(48589), None),
656 // Attributes scoped to tools
657 (accepted, tool_attributes, "1.30.0", Some(44690), None),
658 // Allows multi-segment paths in attributes and derives
659 (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
660 // Allows all literals in attribute lists and values of key-value pairs.
661 (accepted, attr_literals, "1.30.0", Some(34981), None),
662 // Infer outlives requirements; RFC 2093
663 (accepted, infer_outlives_requirements, "1.30.0", Some(44493), None),
664 (accepted, panic_handler, "1.30.0", Some(44489), None),
665 // Used to preserve symbols (see llvm.used)
666 (accepted, used, "1.30.0", Some(40289), None),
668 (accepted, crate_in_paths, "1.30.0", Some(45477), None),
669 // Resolve absolute paths as paths from other crates
670 (accepted, extern_absolute_paths, "1.30.0", Some(44660), None),
671 // Access to crate names passed via `--extern` through prelude
672 (accepted, extern_prelude, "1.30.0", Some(44660), None),
673 // Parentheses in patterns
674 (accepted, pattern_parentheses, "1.31.0", Some(51087), None),
675 // Allows the definition of `const fn` functions
676 (accepted, min_const_fn, "1.31.0", Some(53555), None),
678 (accepted, tool_lints, "1.31.0", Some(44690), None),
679 // impl<I:Iterator> Iterator for &mut Iterator
680 // impl Debug for Foo<'_>
681 (accepted, impl_header_lifetime_elision, "1.31.0", Some(15872), None),
682 // `extern crate foo as bar;` puts `bar` into extern prelude
683 (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
684 // Allows use of the :literal macro fragment specifier (RFC 1576)
685 (accepted, macro_literal_matcher, "1.31.0", Some(35625), None),
686 // Use `?` as the Kleene "at most one" operator
687 (accepted, macro_at_most_once_rep, "1.32.0", Some(48075), None),
688 // `Self` struct constructor (RFC 2302)
689 (accepted, self_struct_ctor, "1.32.0", Some(51994), None),
690 // `Self` in type definitions (RFC 2300)
691 (accepted, self_in_typedefs, "1.32.0", Some(49303), None),
694 // If you change this, please modify `src/doc/unstable-book` as well. You must
695 // move that documentation into the relevant place in the other docs, and
696 // remove the chapter on the flag.
698 #[derive(Copy, Clone, PartialEq, Debug)]
699 pub enum AttributeType {
700 /// Normal, builtin attribute that is consumed
701 /// by the compiler before the unused_attribute check
704 /// Builtin attribute that may not be consumed by the compiler
705 /// before the unused_attribute check. These attributes
706 /// will be ignored by the unused_attribute lint
709 /// Builtin attribute that is only allowed at the crate level
713 pub enum AttributeGate {
714 /// Is gated by a given feature gate, reason
715 /// and function to check if enabled
716 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
718 /// Ungated attribute, can be used on all release channels
723 fn is_deprecated(&self) -> bool {
725 Gated(Stability::Deprecated(_, _), ..) => true,
731 #[derive(Copy, Clone, Debug)]
734 // First argument is tracking issue link; second argument is an optional
735 // help message, which defaults to "remove this attribute"
736 Deprecated(&'static str, Option<&'static str>),
740 impl ::std::fmt::Debug for AttributeGate {
741 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
743 Gated(ref stab, name, expl, _) =>
744 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
745 Ungated => write!(fmt, "Ungated")
750 macro_rules! cfg_fn {
751 ($field: ident) => {{
752 fn f(features: &Features) -> bool {
755 f as fn(&Features) -> bool
759 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
760 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
763 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
764 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
767 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
768 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
771 // Attributes that have a special meaning to rustc or rustdoc
772 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
775 ("warn", Normal, Ungated),
776 ("allow", Normal, Ungated),
777 ("forbid", Normal, Ungated),
778 ("deny", Normal, Ungated),
780 ("macro_use", Normal, Ungated),
781 ("macro_export", Normal, Ungated),
782 ("plugin_registrar", Normal, Ungated),
784 ("cfg", Normal, Ungated),
785 ("cfg_attr", Normal, Ungated),
786 ("main", Normal, Ungated),
787 ("start", Normal, Ungated),
788 ("repr", Normal, Ungated),
789 ("path", Normal, Ungated),
790 ("abi", Normal, Ungated),
791 ("automatically_derived", Normal, Ungated),
792 ("no_mangle", Normal, Ungated),
793 ("no_link", Normal, Ungated),
794 ("derive", Normal, Ungated),
795 ("should_panic", Normal, Ungated),
796 ("ignore", Normal, Ungated),
797 ("no_implicit_prelude", Normal, Ungated),
798 ("reexport_test_harness_main", Normal, Ungated),
799 ("link_args", Normal, Gated(Stability::Unstable,
801 "the `link_args` attribute is experimental and not \
802 portable across platforms, it is recommended to \
803 use `#[link(name = \"foo\")] instead",
804 cfg_fn!(link_args))),
805 ("macro_escape", Normal, Ungated),
808 ("structural_match", Whitelisted, Gated(Stability::Unstable,
810 "the semantics of constant patterns is \
812 cfg_fn!(structural_match))),
815 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
817 "non exhaustive is an experimental feature",
818 cfg_fn!(non_exhaustive))),
821 ("marker", Normal, Gated(Stability::Unstable,
823 "marker traits is an experimental feature",
824 cfg_fn!(marker_trait_attr))),
826 ("plugin", CrateLevel, Gated(Stability::Unstable,
828 "compiler plugins are experimental \
832 ("no_std", CrateLevel, Ungated),
833 ("no_core", CrateLevel, Gated(Stability::Unstable,
835 "no_core is experimental",
837 ("lang", Normal, Gated(Stability::Unstable,
839 "language items are subject to change",
840 cfg_fn!(lang_items))),
841 ("linkage", Whitelisted, Gated(Stability::Unstable,
843 "the `linkage` attribute is experimental \
844 and not portable across platforms",
846 ("thread_local", Whitelisted, Gated(Stability::Unstable,
848 "`#[thread_local]` is an experimental feature, and does \
849 not currently handle destructors.",
850 cfg_fn!(thread_local))),
852 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
854 "the `#[rustc_on_unimplemented]` attribute \
855 is an experimental feature",
856 cfg_fn!(on_unimplemented))),
857 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
858 "rustc_const_unstable",
859 "the `#[rustc_const_unstable]` attribute \
860 is an internal feature",
861 cfg_fn!(rustc_const_unstable))),
862 ("global_allocator", Normal, Ungated),
863 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
864 "allocator_internals",
865 "the `#[default_lib_allocator]` \
866 attribute is an experimental feature",
867 cfg_fn!(allocator_internals))),
868 ("needs_allocator", Normal, Gated(Stability::Unstable,
869 "allocator_internals",
870 "the `#[needs_allocator]` \
871 attribute is an experimental \
873 cfg_fn!(allocator_internals))),
874 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
876 "the `#[panic_runtime]` attribute is \
877 an experimental feature",
878 cfg_fn!(panic_runtime))),
879 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
880 "needs_panic_runtime",
881 "the `#[needs_panic_runtime]` \
882 attribute is an experimental \
884 cfg_fn!(needs_panic_runtime))),
885 ("rustc_outlives", Normal, Gated(Stability::Unstable,
887 "the `#[rustc_outlives]` attribute \
888 is just used for rustc unit tests \
889 and will never be stable",
890 cfg_fn!(rustc_attrs))),
891 ("rustc_variance", Normal, Gated(Stability::Unstable,
893 "the `#[rustc_variance]` attribute \
894 is just used for rustc unit tests \
895 and will never be stable",
896 cfg_fn!(rustc_attrs))),
897 ("rustc_regions", Normal, Gated(Stability::Unstable,
899 "the `#[rustc_regions]` attribute \
900 is just used for rustc unit tests \
901 and will never be stable",
902 cfg_fn!(rustc_attrs))),
903 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
905 "the `#[rustc_error]` attribute \
906 is just used for rustc unit tests \
907 and will never be stable",
908 cfg_fn!(rustc_attrs))),
909 ("rustc_dump_user_substs", Whitelisted, Gated(Stability::Unstable,
912 is just used for rustc unit tests \
913 and will never be stable",
914 cfg_fn!(rustc_attrs))),
915 ("rustc_if_this_changed", 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_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
923 "the `#[rustc_if_this_changed]` attribute \
924 is just used for rustc unit tests \
925 and will never be stable",
926 cfg_fn!(rustc_attrs))),
927 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
929 "the `#[rustc_dirty]` attribute \
930 is just used for rustc unit tests \
931 and will never be stable",
932 cfg_fn!(rustc_attrs))),
933 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
935 "the `#[rustc_clean]` attribute \
936 is just used for rustc unit tests \
937 and will never be stable",
938 cfg_fn!(rustc_attrs))),
939 ("rustc_partition_reused", 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_partition_codegened", 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_expected_cgu_reuse", 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_synthetic", Whitelisted, Gated(Stability::Unstable,
960 is just used for rustc unit tests \
961 and will never be stable",
962 cfg_fn!(rustc_attrs))),
963 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
965 "internal rustc attributes will never be stable",
966 cfg_fn!(rustc_attrs))),
967 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
969 "internal rustc attributes will never be stable",
970 cfg_fn!(rustc_attrs))),
971 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
973 "the `#[rustc_mir]` attribute \
974 is just used for rustc unit tests \
975 and will never be stable",
976 cfg_fn!(rustc_attrs))),
977 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
979 "the `#[rustc_inherit_overflow_checks]` \
980 attribute is just used to control \
981 overflow checking behavior of several \
982 libcore functions that are inlined \
983 across crates and will never be stable",
984 cfg_fn!(rustc_attrs))),
986 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
988 "the `#[rustc_dump_program_clauses]` \
989 attribute is just used for rustc unit \
990 tests and will never be stable",
991 cfg_fn!(rustc_attrs))),
992 ("rustc_test_marker", Normal, Gated(Stability::Unstable,
994 "the `#[rustc_test_marker]` attribute \
995 is used internally to track tests",
996 cfg_fn!(rustc_attrs))),
997 ("rustc_transparent_macro", Whitelisted, Gated(Stability::Unstable,
999 "used internally for testing macro hygiene",
1000 cfg_fn!(rustc_attrs))),
1003 ("nll", Whitelisted, Gated(Stability::Unstable,
1005 "Non lexical lifetimes",
1007 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
1008 "compiler_builtins",
1009 "the `#[compiler_builtins]` attribute is used to \
1010 identify the `compiler_builtins` crate which \
1011 contains compiler-rt intrinsics and will never be \
1013 cfg_fn!(compiler_builtins))),
1014 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
1015 "sanitizer_runtime",
1016 "the `#[sanitizer_runtime]` attribute is used to \
1017 identify crates that contain the runtime of a \
1018 sanitizer and will never be stable",
1019 cfg_fn!(sanitizer_runtime))),
1020 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
1022 "the `#[profiler_runtime]` attribute is used to \
1023 identify the `profiler_builtins` crate which \
1024 contains the profiler runtime and will never be \
1026 cfg_fn!(profiler_runtime))),
1028 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
1029 "allow_internal_unstable",
1030 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
1031 cfg_fn!(allow_internal_unstable))),
1033 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
1034 "allow_internal_unsafe",
1035 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
1036 cfg_fn!(allow_internal_unsafe))),
1038 ("fundamental", Whitelisted, Gated(Stability::Unstable,
1040 "the `#[fundamental]` attribute \
1041 is an experimental feature",
1042 cfg_fn!(fundamental))),
1044 ("proc_macro_derive", Normal, Ungated),
1046 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
1048 "internal implementation detail",
1049 cfg_fn!(rustc_attrs))),
1051 // FIXME: #14408 whitelist docs since rustdoc looks at them
1052 ("doc", Whitelisted, Ungated),
1054 // FIXME: #14406 these are processed in codegen, which happens after the
1056 ("cold", Whitelisted, Ungated),
1057 ("naked", Whitelisted, Gated(Stability::Unstable,
1059 "the `#[naked]` attribute \
1060 is an experimental feature",
1061 cfg_fn!(naked_functions))),
1062 ("target_feature", Whitelisted, Ungated),
1063 ("export_name", Whitelisted, Ungated),
1064 ("inline", Whitelisted, Ungated),
1065 ("link", Whitelisted, Ungated),
1066 ("link_name", Whitelisted, Ungated),
1067 ("link_section", Whitelisted, Ungated),
1068 ("no_builtins", Whitelisted, Ungated),
1069 ("no_mangle", Whitelisted, Ungated),
1070 ("no_debug", Whitelisted, Gated(
1071 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
1073 "the `#[no_debug]` attribute was an experimental feature that has been \
1074 deprecated due to lack of demand",
1075 cfg_fn!(no_debug))),
1076 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
1077 "omit_gdb_pretty_printer_section",
1078 "the `#[omit_gdb_pretty_printer_section]` \
1079 attribute is just used for the Rust test \
1081 cfg_fn!(omit_gdb_pretty_printer_section))),
1082 ("unsafe_destructor_blind_to_params",
1084 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761",
1085 Some("replace this attribute with `#[may_dangle]`")),
1086 "dropck_parametricity",
1087 "unsafe_destructor_blind_to_params has been replaced by \
1088 may_dangle and will be removed in the future",
1089 cfg_fn!(dropck_parametricity))),
1092 Gated(Stability::Unstable,
1094 "may_dangle has unstable semantics and may be removed in the future",
1095 cfg_fn!(dropck_eyepatch))),
1096 ("unwind", Whitelisted, Gated(Stability::Unstable,
1097 "unwind_attributes",
1098 "#[unwind] is experimental",
1099 cfg_fn!(unwind_attributes))),
1100 ("used", Whitelisted, Ungated),
1103 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1105 "`#[prelude_import]` is for use by rustc only",
1106 cfg_fn!(prelude_import))),
1108 // FIXME: #14407 these are only looked at on-demand so we can't
1109 // guarantee they'll have already been checked
1110 ("rustc_deprecated", Whitelisted, Ungated),
1111 ("must_use", Whitelisted, Ungated),
1112 ("stable", Whitelisted, Ungated),
1113 ("unstable", Whitelisted, Ungated),
1114 ("deprecated", Normal, Ungated),
1116 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1118 "unboxed_closures are still evolving",
1119 cfg_fn!(unboxed_closures))),
1121 ("windows_subsystem", Whitelisted, Ungated),
1123 ("proc_macro_attribute", Normal, Ungated),
1124 ("proc_macro", Normal, Ungated),
1126 ("rustc_proc_macro_decls", Normal, Gated(Stability::Unstable,
1127 "rustc_proc_macro_decls",
1128 "used internally by rustc",
1129 cfg_fn!(rustc_attrs))),
1131 ("allow_fail", Normal, Gated(Stability::Unstable,
1133 "allow_fail attribute is currently unstable",
1134 cfg_fn!(allow_fail))),
1136 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1138 "this is an internal attribute that will \
1140 cfg_fn!(rustc_attrs))),
1142 // whitelists "identity-like" conversion methods to suggest on type mismatch
1143 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1145 "this is an internal attribute that will \
1147 cfg_fn!(rustc_attrs))),
1149 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1151 "never will be stable",
1152 cfg_fn!(rustc_attrs))),
1155 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1156 "infer_static_outlives_requirements",
1157 "infer 'static lifetime requirements",
1158 cfg_fn!(infer_static_outlives_requirements))),
1161 ("panic_handler", Normal, Ungated),
1163 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1164 "alloc_error_handler",
1165 "#[alloc_error_handler] is an unstable feature",
1166 cfg_fn!(alloc_error_handler))),
1168 // Crate level attributes
1169 ("crate_name", CrateLevel, Ungated),
1170 ("crate_type", CrateLevel, Ungated),
1171 ("crate_id", CrateLevel, Ungated),
1172 ("feature", CrateLevel, Ungated),
1173 ("no_start", CrateLevel, Ungated),
1174 ("no_main", CrateLevel, Ungated),
1175 ("no_builtins", CrateLevel, Ungated),
1176 ("recursion_limit", CrateLevel, Ungated),
1177 ("type_length_limit", CrateLevel, Ungated),
1178 ("test_runner", CrateLevel, Gated(Stability::Unstable,
1179 "custom_test_frameworks",
1180 EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
1181 cfg_fn!(custom_test_frameworks))),
1184 // cfg(...)'s that are feature gated
1185 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1186 // (name in cfg, feature, function to check if the feature is enabled)
1187 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1188 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1189 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1190 ("rustdoc", "doc_cfg", cfg_fn!(doc_cfg)),
1194 pub struct GatedCfg {
1200 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1201 let name = cfg.name().as_str();
1203 .position(|info| info.0 == name)
1212 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1213 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1214 if !has_feature(features) && !self.span.allows_unstable() {
1215 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1216 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1221 struct Context<'a> {
1222 features: &'a Features,
1223 parse_sess: &'a ParseSess,
1224 plugin_attributes: &'a [(String, AttributeType)],
1227 macro_rules! gate_feature_fn {
1228 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1229 let (cx, has_feature, span,
1230 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1231 let has_feature: bool = has_feature(&$cx.features);
1232 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1233 if !has_feature && !span.allows_unstable() {
1234 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1240 macro_rules! gate_feature {
1241 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1242 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1243 stringify!($feature), $explain, GateStrength::Hard)
1245 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1246 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1247 stringify!($feature), $explain, $level)
1251 impl<'a> Context<'a> {
1252 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1253 debug!("check_attribute(attr = {:?})", attr);
1254 let name = attr.name().as_str();
1255 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1257 if let Gated(_, name, desc, ref has_feature) = *gateage {
1258 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1259 } else if name == "doc" {
1260 if let Some(content) = attr.meta_item_list() {
1261 if content.iter().any(|c| c.check_name("include")) {
1262 gate_feature!(self, external_doc, attr.span,
1263 "#[doc(include = \"...\")] is experimental"
1268 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1272 for &(ref n, ref ty) in self.plugin_attributes {
1273 if attr.path == &**n {
1274 // Plugins can't gate attributes, so we don't check for it
1275 // unlike the code above; we only use this loop to
1276 // short-circuit to avoid the checks below
1277 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1281 if name.starts_with("rustc_") {
1282 gate_feature!(self, rustc_attrs, attr.span,
1283 "unless otherwise specified, attributes \
1284 with the prefix `rustc_` \
1285 are reserved for internal compiler diagnostics");
1286 } else if name.starts_with("derive_") {
1287 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1288 } else if !attr::is_known(attr) {
1289 // Only run the custom attribute lint during regular
1290 // feature gate checking. Macro gating runs
1291 // before the plugin attributes are registered
1292 // so we skip this then
1294 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1295 may have meaning added to it in the future", attr.path);
1296 gate_feature!(self, custom_attribute, attr.span, &msg);
1302 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1303 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1304 cx.check_attribute(attr, true);
1307 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1308 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1310 // FIXME (#28244): enforce that active features have issue numbers
1311 // assert!(issue.is_some())
1314 // search in Accepted, Removed, or Stable Removed features
1315 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1316 .find(|t| t.0 == feature);
1318 Some(&(_, _, issue, _)) => issue,
1319 None => panic!("Feature `{}` is not declared anywhere", feature),
1324 pub enum GateIssue {
1326 Library(Option<u32>)
1329 #[derive(Debug, Copy, Clone, PartialEq)]
1330 pub enum GateStrength {
1331 /// A hard error. (Most feature gates should use this.)
1333 /// Only a warning. (Use this only as backwards-compatibility demands.)
1337 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1339 feature_err(sess, feature, span, issue, explain).emit();
1342 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1343 explain: &str) -> DiagnosticBuilder<'a> {
1344 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1347 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1348 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1349 let diag = &sess.span_diagnostic;
1351 let issue = match issue {
1352 GateIssue::Language => find_lang_feature_issue(feature),
1353 GateIssue::Library(lib) => lib,
1356 let explanation = match issue {
1357 None | Some(0) => explain.to_owned(),
1358 Some(n) => format!("{} (see issue #{})", explain, n)
1361 let mut err = match level {
1362 GateStrength::Hard => {
1363 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1365 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1368 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1369 if sess.unstable_features.is_nightly_build() {
1370 err.help(&format!("add #![feature({})] to the \
1371 crate attributes to enable",
1375 // If we're on stable and only emitting a "soft" warning, add a note to
1376 // clarify that the feature isn't "on" (rather than being on but
1378 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1379 err.help("a nightly build of the compiler is required to enable this feature");
1386 const EXPLAIN_BOX_SYNTAX: &'static str =
1387 "box expression syntax is experimental; you can call `Box::new` instead.";
1389 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1390 "attributes on expressions are experimental.";
1392 pub const EXPLAIN_ASM: &'static str =
1393 "inline assembly is not stable enough for use and is subject to change";
1395 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1396 "`global_asm!` is not stable enough for use and is subject to change";
1398 pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &'static str =
1399 "custom test frameworks are an unstable feature";
1401 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1402 "`log_syntax!` is not stable enough for use and is subject to change";
1404 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1405 "`concat_idents` is not stable enough for use and is subject to change";
1407 pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
1408 "`format_args_nl` is only for internal language use and is subject to change";
1410 pub const EXPLAIN_TRACE_MACROS: &'static str =
1411 "`trace_macros` is not stable enough for use and is subject to change";
1412 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1413 "allow_internal_unstable side-steps feature gating and stability checks";
1414 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1415 "allow_internal_unsafe side-steps the unsafe_code lint";
1417 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1418 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1420 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1421 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1422 Prefer using procedural macro custom derive.";
1424 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1425 "attributes of the form `#[derive_*]` are reserved for the compiler";
1427 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1428 "unsized tuple coercion is not stable enough for use and is subject to change";
1430 struct PostExpansionVisitor<'a> {
1431 context: &'a Context<'a>,
1434 macro_rules! gate_feature_post {
1435 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1436 let (cx, span) = ($cx, $span);
1437 if !span.allows_unstable() {
1438 gate_feature!(cx.context, $feature, span, $explain)
1441 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1442 let (cx, span) = ($cx, $span);
1443 if !span.allows_unstable() {
1444 gate_feature!(cx.context, $feature, span, $explain, $level)
1449 impl<'a> PostExpansionVisitor<'a> {
1450 fn check_abi(&self, abi: Abi, span: Span) {
1452 Abi::RustIntrinsic => {
1453 gate_feature_post!(&self, intrinsics, span,
1454 "intrinsics are subject to change");
1456 Abi::PlatformIntrinsic => {
1457 gate_feature_post!(&self, platform_intrinsics, span,
1458 "platform intrinsics are experimental and possibly buggy");
1460 Abi::Vectorcall => {
1461 gate_feature_post!(&self, abi_vectorcall, span,
1462 "vectorcall is experimental and subject to change");
1465 gate_feature_post!(&self, abi_thiscall, span,
1466 "thiscall is experimental and subject to change");
1469 gate_feature_post!(&self, unboxed_closures, span,
1470 "rust-call ABI is subject to change");
1473 gate_feature_post!(&self, abi_ptx, span,
1474 "PTX ABIs are experimental and subject to change");
1476 Abi::Unadjusted => {
1477 gate_feature_post!(&self, abi_unadjusted, span,
1478 "unadjusted ABI is an implementation detail and perma-unstable");
1480 Abi::Msp430Interrupt => {
1481 gate_feature_post!(&self, abi_msp430_interrupt, span,
1482 "msp430-interrupt ABI is experimental and subject to change");
1484 Abi::X86Interrupt => {
1485 gate_feature_post!(&self, abi_x86_interrupt, span,
1486 "x86-interrupt ABI is experimental and subject to change");
1488 Abi::AmdGpuKernel => {
1489 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1490 "amdgpu-kernel ABI is experimental and subject to change");
1506 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1507 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1508 if !attr.span.allows_unstable() {
1509 // check for gated attributes
1510 self.context.check_attribute(attr, false);
1513 if attr.check_name("doc") {
1514 if let Some(content) = attr.meta_item_list() {
1515 if content.len() == 1 && content[0].check_name("cfg") {
1516 gate_feature_post!(&self, doc_cfg, attr.span,
1517 "#[doc(cfg(...))] is experimental"
1519 } else if content.iter().any(|c| c.check_name("masked")) {
1520 gate_feature_post!(&self, doc_masked, attr.span,
1521 "#[doc(masked)] is experimental"
1523 } else if content.iter().any(|c| c.check_name("spotlight")) {
1524 gate_feature_post!(&self, doc_spotlight, attr.span,
1525 "#[doc(spotlight)] is experimental"
1527 } else if content.iter().any(|c| c.check_name("alias")) {
1528 gate_feature_post!(&self, doc_alias, attr.span,
1529 "#[doc(alias = \"...\")] is experimental"
1531 } else if content.iter().any(|c| c.check_name("keyword")) {
1532 gate_feature_post!(&self, doc_keyword, attr.span,
1533 "#[doc(keyword = \"...\")] is experimental"
1539 if !self.context.features.unrestricted_attribute_tokens {
1540 // Unfortunately, `parse_meta` cannot be called speculatively
1541 // because it can report errors by itself, so we have to call it
1542 // only if the feature is disabled.
1543 if let Err(mut err) = attr.parse_meta(self.context.parse_sess) {
1544 err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
1549 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1550 if !name.as_str().is_ascii() {
1551 gate_feature_post!(&self,
1553 self.context.parse_sess.source_map().def_span(sp),
1554 "non-ascii idents are not fully supported.");
1558 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1559 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1560 if ident.name == "_" {
1561 gate_feature_post!(&self, underscore_imports, use_tree.span,
1562 "renaming imports with `_` is unstable");
1566 visit::walk_use_tree(self, use_tree, id);
1569 fn visit_item(&mut self, i: &'a ast::Item) {
1571 ast::ItemKind::ExternCrate(_) => {
1572 if i.ident.name == "_" {
1573 gate_feature_post!(&self, underscore_imports, i.span,
1574 "renaming extern crates with `_` is unstable");
1578 ast::ItemKind::Static(..) |
1579 ast::ItemKind::Const(_,_) => {
1580 if i.ident.name == "_" {
1581 gate_feature_post!(&self, underscore_const_names, i.span,
1582 "naming constants with `_` is unstable");
1586 ast::ItemKind::ForeignMod(ref foreign_module) => {
1587 self.check_abi(foreign_module.abi, i.span);
1590 ast::ItemKind::Fn(..) => {
1591 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1592 gate_feature_post!(&self, plugin_registrar, i.span,
1593 "compiler plugins are experimental and possibly buggy");
1595 if attr::contains_name(&i.attrs[..], "start") {
1596 gate_feature_post!(&self, start, i.span,
1597 "a #[start] function is an experimental \
1598 feature whose signature may change \
1601 if attr::contains_name(&i.attrs[..], "main") {
1602 gate_feature_post!(&self, main, i.span,
1603 "declaration of a nonstandard #[main] \
1604 function may change over time, for now \
1605 a top-level `fn main()` is required");
1609 ast::ItemKind::Struct(..) => {
1610 for attr in attr::filter_by_name(&i.attrs[..], "repr") {
1611 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1612 if item.check_name("simd") {
1613 gate_feature_post!(&self, repr_simd, attr.span,
1614 "SIMD types are experimental and possibly buggy");
1616 if let Some((name, _)) = item.name_value_literal() {
1617 if name == "packed" {
1618 gate_feature_post!(&self, repr_packed, attr.span,
1619 "the `#[repr(packed(n))]` attribute \
1627 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1628 if polarity == ast::ImplPolarity::Negative {
1629 gate_feature_post!(&self, optin_builtin_traits,
1631 "negative trait bounds are not yet fully implemented; \
1632 use marker types for now");
1635 if let ast::Defaultness::Default = defaultness {
1636 gate_feature_post!(&self, specialization,
1638 "specialization is unstable");
1642 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1643 gate_feature_post!(&self, optin_builtin_traits,
1645 "auto traits are experimental and possibly buggy");
1648 ast::ItemKind::TraitAlias(..) => {
1653 "trait aliases are experimental"
1657 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1658 let msg = "`macro` is experimental";
1659 gate_feature_post!(&self, decl_macro, i.span, msg);
1662 ast::ItemKind::Existential(..) => {
1667 "existential types are unstable"
1674 visit::walk_item(self, i);
1677 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1679 ast::ForeignItemKind::Fn(..) |
1680 ast::ForeignItemKind::Static(..) => {
1681 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1682 let links_to_llvm = match link_name {
1683 Some(val) => val.as_str().starts_with("llvm."),
1687 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1688 "linking to LLVM intrinsics is experimental");
1691 ast::ForeignItemKind::Ty => {
1692 gate_feature_post!(&self, extern_types, i.span,
1693 "extern types are experimental");
1695 ast::ForeignItemKind::Macro(..) => {}
1698 visit::walk_foreign_item(self, i)
1701 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1703 ast::TyKind::BareFn(ref bare_fn_ty) => {
1704 self.check_abi(bare_fn_ty.abi, ty.span);
1706 ast::TyKind::Never => {
1707 gate_feature_post!(&self, never_type, ty.span,
1708 "The `!` type is experimental");
1712 visit::walk_ty(self, ty)
1715 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1716 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1717 if let ast::TyKind::Never = output_ty.node {
1720 self.visit_ty(output_ty)
1725 fn visit_expr(&mut self, e: &'a ast::Expr) {
1727 ast::ExprKind::Box(_) => {
1728 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1730 ast::ExprKind::Type(..) => {
1731 gate_feature_post!(&self, type_ascription, e.span,
1732 "type ascription is experimental");
1734 ast::ExprKind::ObsoleteInPlace(..) => {
1735 // these get a hard error in ast-validation
1737 ast::ExprKind::Yield(..) => {
1738 gate_feature_post!(&self, generators,
1740 "yield syntax is experimental");
1742 ast::ExprKind::TryBlock(_) => {
1743 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
1745 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1747 gate_feature_post!(&self, if_while_or_patterns, e.span,
1748 "multiple patterns in `if let` and `while let` are unstable");
1751 ast::ExprKind::Block(_, opt_label) => {
1752 if let Some(label) = opt_label {
1753 gate_feature_post!(&self, label_break_value, label.ident.span,
1754 "labels on blocks are unstable");
1757 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1758 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1760 ast::ExprKind::Async(..) => {
1761 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1765 visit::walk_expr(self, e);
1768 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1769 visit::walk_arm(self, arm)
1772 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1773 match pattern.node {
1774 PatKind::Slice(_, Some(ref subslice), _) => {
1775 gate_feature_post!(&self, slice_patterns,
1777 "syntax for subslices in slice patterns is not yet stabilized");
1779 PatKind::Box(..) => {
1780 gate_feature_post!(&self, box_patterns,
1782 "box pattern syntax is experimental");
1784 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1785 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1786 "exclusive range pattern syntax is experimental");
1790 visit::walk_pat(self, pattern)
1793 fn visit_fn(&mut self,
1794 fn_kind: FnKind<'a>,
1795 fn_decl: &'a ast::FnDecl,
1799 FnKind::ItemFn(_, header, _, _) => {
1800 // check for const fn and async fn declarations
1801 if header.asyncness.is_async() {
1802 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1804 // stability of const fn methods are covered in
1805 // visit_trait_item and visit_impl_item below; this is
1806 // because default methods don't pass through this
1809 self.check_abi(header.abi, span);
1811 FnKind::Method(_, sig, _, _) => {
1812 self.check_abi(sig.header.abi, span);
1816 visit::walk_fn(self, fn_kind, fn_decl, span);
1819 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1821 ast::TraitItemKind::Method(ref sig, ref block) => {
1822 if block.is_none() {
1823 self.check_abi(sig.header.abi, ti.span);
1825 if sig.header.constness.node == ast::Constness::Const {
1826 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1829 ast::TraitItemKind::Type(_, ref default) => {
1830 // We use three if statements instead of something like match guards so that all
1831 // of these errors can be emitted if all cases apply.
1832 if default.is_some() {
1833 gate_feature_post!(&self, associated_type_defaults, ti.span,
1834 "associated type defaults are unstable");
1836 if !ti.generics.params.is_empty() {
1837 gate_feature_post!(&self, generic_associated_types, ti.span,
1838 "generic associated types are unstable");
1840 if !ti.generics.where_clause.predicates.is_empty() {
1841 gate_feature_post!(&self, generic_associated_types, ti.span,
1842 "where clauses on associated types are unstable");
1847 visit::walk_trait_item(self, ti);
1850 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1851 if ii.defaultness == ast::Defaultness::Default {
1852 gate_feature_post!(&self, specialization,
1854 "specialization is unstable");
1858 ast::ImplItemKind::Method(..) => {}
1859 ast::ImplItemKind::Existential(..) => {
1864 "existential types are unstable"
1867 ast::ImplItemKind::Type(_) => {
1868 if !ii.generics.params.is_empty() {
1869 gate_feature_post!(&self, generic_associated_types, ii.span,
1870 "generic associated types are unstable");
1872 if !ii.generics.where_clause.predicates.is_empty() {
1873 gate_feature_post!(&self, generic_associated_types, ii.span,
1874 "where clauses on associated types are unstable");
1879 visit::walk_impl_item(self, ii);
1882 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1883 for segment in &path.segments {
1884 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1885 // For such macros identifiers must have empty context, because this context is
1886 // used during name resolution and produced names must be unhygienic for compatibility.
1887 // On the other hand, we need the actual non-empty context for feature gate checking
1888 // because it's hygienic even for legacy macros. As previously stated, such context
1889 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1890 // there while keeping location info from the ident span.
1891 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1892 if segment.ident.name == keywords::Extern.name() {
1893 gate_feature_post!(&self, extern_in_paths, span,
1894 "`extern` in paths is experimental");
1898 visit::walk_path(self, path);
1901 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1902 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1903 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1904 "`crate` visibility modifier is experimental");
1906 visit::walk_vis(self, vis);
1910 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1911 crate_edition: Edition) -> Features {
1912 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1913 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1914 if let Some(reason) = reason {
1915 err.span_note(span, reason);
1920 // Some features are known to be incomplete and using them is likely to have
1921 // unanticipated results, such as compiler crashes. We warn the user about these
1923 let incomplete_features = ["generic_associated_types"];
1925 let mut features = Features::new();
1926 let mut edition_enabled_features = FxHashMap::default();
1928 for &edition in ALL_EDITIONS {
1929 if edition <= crate_edition {
1930 // The `crate_edition` implies its respective umbrella feature-gate
1931 // (i.e. `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
1932 edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
1936 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1937 if let Some(f_edition) = f_edition {
1938 if f_edition <= crate_edition {
1939 set(&mut features, DUMMY_SP);
1940 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1945 // Process the edition umbrella feature-gates first, to ensure
1946 // `edition_enabled_features` is completed before it's queried.
1947 for attr in krate_attrs {
1948 if !attr.check_name("feature") {
1952 let list = match attr.meta_item_list() {
1958 let name = if let Some(word) = mi.word() {
1964 if incomplete_features.iter().any(|f| *f == name.as_str()) {
1965 span_handler.struct_span_warn(
1968 "the feature `{}` is incomplete and may cause the compiler to crash",
1974 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1975 if *edition <= crate_edition {
1979 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1980 if let Some(f_edition) = f_edition {
1981 if f_edition <= *edition {
1982 // FIXME(Manishearth) there is currently no way to set
1983 // lib features by edition
1984 set(&mut features, DUMMY_SP);
1985 edition_enabled_features.insert(Symbol::intern(name), *edition);
1993 for attr in krate_attrs {
1994 if !attr.check_name("feature") {
1998 let list = match attr.meta_item_list() {
2001 span_err!(span_handler, attr.span, E0555,
2002 "malformed feature attribute, expected #![feature(...)]");
2008 let name = if let Some(word) = mi.word() {
2011 span_err!(span_handler, mi.span, E0556,
2012 "malformed feature, expected just one word");
2016 if let Some(edition) = edition_enabled_features.get(&name) {
2021 "the feature `{}` is included in the Rust {} edition",
2028 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
2029 // Handled in the separate loop above.
2033 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
2034 set(&mut features, mi.span);
2035 features.declared_lang_features.push((name, mi.span, None));
2039 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
2040 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
2041 if let Some((.., reason)) = removed.or(stable_removed) {
2042 feature_removed(span_handler, mi.span, *reason);
2046 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
2047 let since = Some(Symbol::intern(since));
2048 features.declared_lang_features.push((name, mi.span, since));
2052 features.declared_lib_features.push((name, mi.span));
2059 pub fn check_crate(krate: &ast::Crate,
2061 features: &Features,
2062 plugin_attributes: &[(String, AttributeType)],
2063 unstable: UnstableFeatures) {
2064 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2071 let visitor = &mut PostExpansionVisitor { context: &ctx };
2072 visit::walk_crate(visitor, krate);
2075 #[derive(Clone, Copy, Hash)]
2076 pub enum UnstableFeatures {
2077 /// Hard errors for unstable features are active, as on
2078 /// beta/stable channels.
2080 /// Allow features to be activated, as on nightly.
2082 /// Errors are bypassed for bootstrapping. This is required any time
2083 /// during the build that feature-related lints are set to warn or above
2084 /// because the build turns on warnings-as-errors and uses lots of unstable
2085 /// features. As a result, this is always required for building Rust itself.
2089 impl UnstableFeatures {
2090 pub fn from_environment() -> UnstableFeatures {
2091 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2092 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2093 // Whether we should enable unstable features for bootstrapping
2094 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2095 match (disable_unstable_features, bootstrap) {
2096 (_, true) => UnstableFeatures::Cheat,
2097 (true, _) => UnstableFeatures::Disallow,
2098 (false, _) => UnstableFeatures::Allow
2102 pub fn is_nightly_build(&self) -> bool {
2104 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2110 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2111 unstable: UnstableFeatures) {
2112 let allow_features = match unstable {
2113 UnstableFeatures::Allow => true,
2114 UnstableFeatures::Disallow => false,
2115 UnstableFeatures::Cheat => true
2117 if !allow_features {
2118 for attr in &krate.attrs {
2119 if attr.check_name("feature") {
2120 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2121 span_err!(span_handler, attr.span, E0554,
2122 "#![feature] may not be used on the {} release channel",