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 `Self` in type definitions
466 (active, self_in_typedefs, "1.30.0", Some(49303), None),
468 // Allows unsized rvalues at arguments and parameters
469 (active, unsized_locals, "1.30.0", Some(48055), None),
473 (active, custom_test_frameworks, "1.30.0", Some(50297), None),
475 // Non-builtin attributes in inner attribute position
476 (active, custom_inner_attributes, "1.30.0", Some(54726), None),
478 // Self struct constructor (RFC 2302)
479 (active, self_struct_ctor, "1.30.0", Some(51994), None),
481 // allow mixing of bind-by-move in patterns and references to
482 // those identifiers in guards, *if* we are using MIR-borrowck
483 // (aka NLL). Essentially this means you need to be on
484 // edition:2018 or later.
485 (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
487 // Allows `impl Trait` in bindings (`let`, `const`, `static`)
488 (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
490 // #[cfg_attr(predicate, multiple, attributes, here)]
491 (active, cfg_attr_multi, "1.31.0", Some(54881), None),
493 // Allows `const _: TYPE = VALUE`
494 (active, underscore_const_names, "1.31.0", Some(54912), None),
496 // `reason = ` in lint attributes and `expect` lint attribute
497 (active, lint_reasons, "1.31.0", Some(54503), None),
501 (removed, import_shadowing, "1.0.0", None, None, None),
502 (removed, managed_boxes, "1.0.0", None, None, None),
503 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
504 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
505 (removed, reflect, "1.0.0", Some(27749), None, None),
506 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
507 (removed, opt_out_copy, "1.0.0", None, None, None),
508 (removed, quad_precision_float, "1.0.0", None, None, None),
509 (removed, struct_inherit, "1.0.0", None, None, None),
510 (removed, test_removed_feature, "1.0.0", None, None, None),
511 (removed, visible_private_types, "1.0.0", None, None, None),
512 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
513 // Allows using items which are missing stability attributes
515 (removed, unmarked_api, "1.0.0", None, None, None),
516 (removed, pushpop_unsafe, "1.2.0", None, None, None),
517 (removed, allocator, "1.0.0", None, None, None),
518 (removed, simd, "1.0.0", Some(27731), None,
519 Some("removed in favor of `#[repr(simd)]`")),
520 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
521 Some("merged into `#![feature(slice_patterns)]`")),
522 (removed, macro_reexport, "1.0.0", Some(29638), None,
523 Some("subsumed by `pub use`")),
524 (removed, proc_macro_mod, "1.27.0", Some(54727), None,
525 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
526 (removed, proc_macro_expr, "1.27.0", Some(54727), None,
527 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
528 (removed, proc_macro_non_items, "1.27.0", Some(54727), None,
529 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
530 (removed, proc_macro_gen, "1.27.0", Some(54727), None,
531 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
532 (removed, panic_implementation, "1.28.0", Some(44489), None,
533 Some("subsumed by `#[panic_handler]`")),
537 (stable_removed, no_stack_check, "1.0.0", None, None),
541 (accepted, associated_types, "1.0.0", None, None),
542 // allow overloading augmented assignment operations like `a += b`
543 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
544 // allow empty structs and enum variants with braces
545 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
546 // Allows indexing into constant arrays.
547 (accepted, const_indexing, "1.26.0", Some(29947), None),
548 (accepted, default_type_params, "1.0.0", None, None),
549 (accepted, globs, "1.0.0", None, None),
550 (accepted, if_let, "1.0.0", None, None),
551 // A temporary feature gate used to enable parser extensions needed
552 // to bootstrap fix for #5723.
553 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
554 (accepted, macro_rules, "1.0.0", None, None),
555 // Allows using #![no_std]
556 (accepted, no_std, "1.6.0", None, None),
557 (accepted, slicing_syntax, "1.0.0", None, None),
558 (accepted, struct_variant, "1.0.0", None, None),
559 // These are used to test this portion of the compiler, they don't actually
561 (accepted, test_accepted_feature, "1.0.0", None, None),
562 (accepted, tuple_indexing, "1.0.0", None, None),
563 // Allows macros to appear in the type position.
564 (accepted, type_macros, "1.13.0", Some(27245), None),
565 (accepted, while_let, "1.0.0", None, None),
566 // Allows `#[deprecated]` attribute
567 (accepted, deprecated, "1.9.0", Some(29935), None),
569 (accepted, question_mark, "1.13.0", Some(31436), None),
570 // Allows `..` in tuple (struct) patterns
571 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
572 (accepted, item_like_imports, "1.15.0", Some(35120), None),
573 // Allows using `Self` and associated types in struct expressions and patterns.
574 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
575 // elide `'static` lifetimes in `static`s and `const`s
576 (accepted, static_in_const, "1.17.0", Some(35897), None),
577 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
578 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
579 // Allows the definition recursive static items.
580 (accepted, static_recursion, "1.17.0", Some(29719), None),
581 // pub(restricted) visibilities (RFC 1422)
582 (accepted, pub_restricted, "1.18.0", Some(32409), None),
583 // The #![windows_subsystem] attribute
584 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
585 // Allows `break {expr}` with a value inside `loop`s.
586 (accepted, loop_break_value, "1.19.0", Some(37339), None),
587 // Permits numeric fields in struct expressions and patterns.
588 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
589 // Coerces non capturing closures to function pointers
590 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
591 // Allows attributes on struct literal fields.
592 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
593 // Allows the definition of associated constants in `trait` or `impl`
595 (accepted, associated_consts, "1.20.0", Some(29646), None),
596 // Usage of the `compile_error!` macro
597 (accepted, compile_error, "1.20.0", Some(40872), None),
598 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
599 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
600 // Allow Drop types in constants (RFC 1440)
601 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
602 // Allows the sysV64 ABI to be specified on all platforms
603 // instead of just the platforms on which it is the C ABI
604 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
605 // Allows `repr(align(16))` struct attribute (RFC 1358)
606 (accepted, repr_align, "1.25.0", Some(33626), None),
607 // allow '|' at beginning of match arms (RFC 1925)
608 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
609 // Nested groups in `use` (RFC 2128)
610 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
612 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
613 // allow `..=` in patterns (RFC 1192)
614 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
615 // Termination trait in main (RFC 1937)
616 (accepted, termination_trait, "1.26.0", Some(43301), None),
617 // Copy/Clone closures (RFC 2132)
618 (accepted, clone_closures, "1.26.0", Some(44490), None),
619 (accepted, copy_closures, "1.26.0", Some(44490), None),
620 // Allows `impl Trait` in function arguments.
621 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
622 // Allows `impl Trait` in function return types.
623 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
625 (accepted, i128_type, "1.26.0", Some(35118), None),
626 // Default match binding modes (RFC 2005)
627 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
628 // allow `'_` placeholder lifetimes
629 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
630 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
631 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
632 // Allows cfg(target_feature = "...").
633 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
634 // Allows #[target_feature(...)]
635 (accepted, target_feature, "1.27.0", None, None),
636 // Trait object syntax with `dyn` prefix
637 (accepted, dyn_trait, "1.27.0", Some(44662), None),
638 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
639 (accepted, fn_must_use, "1.27.0", Some(43302), None),
640 // Allows use of the :lifetime macro fragment specifier
641 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
642 // Termination trait in tests (RFC 1937)
643 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
644 // The #[global_allocator] attribute
645 (accepted, global_allocator, "1.28.0", Some(27389), None),
646 // Allows `#[repr(transparent)]` attribute on newtype structs
647 (accepted, repr_transparent, "1.28.0", Some(43036), None),
648 // Defining procedural macros in `proc-macro` crates
649 (accepted, proc_macro, "1.29.0", Some(38356), None),
650 // `foo.rs` as an alternative to `foo/mod.rs`
651 (accepted, non_modrs_mods, "1.30.0", Some(44660), None),
652 // Allows use of the :vis macro fragment specifier
653 (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
654 // Allows importing and reexporting macros with `use`,
655 // enables macro modularization in general.
656 (accepted, use_extern_macros, "1.30.0", Some(35896), None),
657 // Allows keywords to be escaped for use as identifiers
658 (accepted, raw_identifiers, "1.30.0", Some(48589), None),
659 // Attributes scoped to tools
660 (accepted, tool_attributes, "1.30.0", Some(44690), None),
661 // Allows multi-segment paths in attributes and derives
662 (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
663 // Allows all literals in attribute lists and values of key-value pairs.
664 (accepted, attr_literals, "1.30.0", Some(34981), None),
665 // Infer outlives requirements; RFC 2093
666 (accepted, infer_outlives_requirements, "1.30.0", Some(44493), None),
667 (accepted, panic_handler, "1.30.0", Some(44489), None),
668 // Used to preserve symbols (see llvm.used)
669 (accepted, used, "1.30.0", Some(40289), None),
671 (accepted, crate_in_paths, "1.30.0", Some(45477), None),
672 // Resolve absolute paths as paths from other crates
673 (accepted, extern_absolute_paths, "1.30.0", Some(44660), None),
674 // Access to crate names passed via `--extern` through prelude
675 (accepted, extern_prelude, "1.30.0", Some(44660), None),
676 // Parentheses in patterns
677 (accepted, pattern_parentheses, "1.31.0", Some(51087), None),
678 // Allows the definition of `const fn` functions.
679 (accepted, min_const_fn, "1.31.0", Some(53555), None),
681 (accepted, tool_lints, "1.31.0", Some(44690), None),
682 // impl<I:Iterator> Iterator for &mut Iterator
683 // impl Debug for Foo<'_>
684 (accepted, impl_header_lifetime_elision, "1.31.0", Some(15872), None),
685 // `extern crate foo as bar;` puts `bar` into extern prelude.
686 (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
687 // Allows use of the :literal macro fragment specifier (RFC 1576)
688 (accepted, macro_literal_matcher, "1.31.0", Some(35625), None),
689 // Use `?` as the Kleene "at most one" operator
690 (accepted, macro_at_most_once_rep, "1.32.0", Some(48075), None),
693 // If you change this, please modify src/doc/unstable-book as well. You must
694 // move that documentation into the relevant place in the other docs, and
695 // remove the chapter on the flag.
697 #[derive(Copy, Clone, PartialEq, Debug)]
698 pub enum AttributeType {
699 /// Normal, builtin attribute that is consumed
700 /// by the compiler before the unused_attribute check
703 /// Builtin attribute that may not be consumed by the compiler
704 /// before the unused_attribute check. These attributes
705 /// will be ignored by the unused_attribute lint
708 /// Builtin attribute that is only allowed at the crate level
712 pub enum AttributeGate {
713 /// Is gated by a given feature gate, reason
714 /// and function to check if enabled
715 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
717 /// Ungated attribute, can be used on all release channels
722 fn is_deprecated(&self) -> bool {
724 Gated(Stability::Deprecated(_, _), ..) => true,
730 #[derive(Copy, Clone, Debug)]
733 // First argument is tracking issue link; second argument is an optional
734 // help message, which defaults to "remove this attribute"
735 Deprecated(&'static str, Option<&'static str>),
739 impl ::std::fmt::Debug for AttributeGate {
740 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
742 Gated(ref stab, name, expl, _) =>
743 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
744 Ungated => write!(fmt, "Ungated")
749 macro_rules! cfg_fn {
750 ($field: ident) => {{
751 fn f(features: &Features) -> bool {
754 f as fn(&Features) -> bool
758 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
759 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
762 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
763 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
766 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
767 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
770 // Attributes that have a special meaning to rustc or rustdoc
771 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
774 ("warn", Normal, Ungated),
775 ("allow", Normal, Ungated),
776 ("forbid", Normal, Ungated),
777 ("deny", Normal, Ungated),
779 ("macro_use", Normal, Ungated),
780 ("macro_export", Normal, Ungated),
781 ("plugin_registrar", Normal, Ungated),
783 ("cfg", Normal, Ungated),
784 ("cfg_attr", Normal, Ungated),
785 ("main", Normal, Ungated),
786 ("start", Normal, Ungated),
787 ("repr", Normal, Ungated),
788 ("path", Normal, Ungated),
789 ("abi", Normal, Ungated),
790 ("automatically_derived", Normal, Ungated),
791 ("no_mangle", Normal, Ungated),
792 ("no_link", Normal, Ungated),
793 ("derive", Normal, Ungated),
794 ("should_panic", Normal, Ungated),
795 ("ignore", Normal, Ungated),
796 ("no_implicit_prelude", Normal, Ungated),
797 ("reexport_test_harness_main", Normal, Ungated),
798 ("link_args", Normal, Gated(Stability::Unstable,
800 "the `link_args` attribute is experimental and not \
801 portable across platforms, it is recommended to \
802 use `#[link(name = \"foo\")] instead",
803 cfg_fn!(link_args))),
804 ("macro_escape", Normal, Ungated),
807 ("structural_match", Whitelisted, Gated(Stability::Unstable,
809 "the semantics of constant patterns is \
811 cfg_fn!(structural_match))),
814 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
816 "non exhaustive is an experimental feature",
817 cfg_fn!(non_exhaustive))),
820 ("marker", Normal, Gated(Stability::Unstable,
822 "marker traits is an experimental feature",
823 cfg_fn!(marker_trait_attr))),
825 ("plugin", CrateLevel, Gated(Stability::Unstable,
827 "compiler plugins are experimental \
831 ("no_std", CrateLevel, Ungated),
832 ("no_core", CrateLevel, Gated(Stability::Unstable,
834 "no_core is experimental",
836 ("lang", Normal, Gated(Stability::Unstable,
838 "language items are subject to change",
839 cfg_fn!(lang_items))),
840 ("linkage", Whitelisted, Gated(Stability::Unstable,
842 "the `linkage` attribute is experimental \
843 and not portable across platforms",
845 ("thread_local", Whitelisted, Gated(Stability::Unstable,
847 "`#[thread_local]` is an experimental feature, and does \
848 not currently handle destructors.",
849 cfg_fn!(thread_local))),
851 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
853 "the `#[rustc_on_unimplemented]` attribute \
854 is an experimental feature",
855 cfg_fn!(on_unimplemented))),
856 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
857 "rustc_const_unstable",
858 "the `#[rustc_const_unstable]` attribute \
859 is an internal feature",
860 cfg_fn!(rustc_const_unstable))),
861 ("global_allocator", Normal, Ungated),
862 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
863 "allocator_internals",
864 "the `#[default_lib_allocator]` \
865 attribute is an experimental feature",
866 cfg_fn!(allocator_internals))),
867 ("needs_allocator", Normal, Gated(Stability::Unstable,
868 "allocator_internals",
869 "the `#[needs_allocator]` \
870 attribute is an experimental \
872 cfg_fn!(allocator_internals))),
873 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
875 "the `#[panic_runtime]` attribute is \
876 an experimental feature",
877 cfg_fn!(panic_runtime))),
878 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
879 "needs_panic_runtime",
880 "the `#[needs_panic_runtime]` \
881 attribute is an experimental \
883 cfg_fn!(needs_panic_runtime))),
884 ("rustc_outlives", Normal, Gated(Stability::Unstable,
886 "the `#[rustc_outlives]` attribute \
887 is just used for rustc unit tests \
888 and will never be stable",
889 cfg_fn!(rustc_attrs))),
890 ("rustc_variance", Normal, Gated(Stability::Unstable,
892 "the `#[rustc_variance]` attribute \
893 is just used for rustc unit tests \
894 and will never be stable",
895 cfg_fn!(rustc_attrs))),
896 ("rustc_regions", Normal, Gated(Stability::Unstable,
898 "the `#[rustc_regions]` attribute \
899 is just used for rustc unit tests \
900 and will never be stable",
901 cfg_fn!(rustc_attrs))),
902 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
904 "the `#[rustc_error]` attribute \
905 is just used for rustc unit tests \
906 and will never be stable",
907 cfg_fn!(rustc_attrs))),
908 ("rustc_dump_user_substs", Whitelisted, Gated(Stability::Unstable,
911 is just used for rustc unit tests \
912 and will never be stable",
913 cfg_fn!(rustc_attrs))),
914 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
916 "the `#[rustc_if_this_changed]` attribute \
917 is just used for rustc unit tests \
918 and will never be stable",
919 cfg_fn!(rustc_attrs))),
920 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
922 "the `#[rustc_if_this_changed]` attribute \
923 is just used for rustc unit tests \
924 and will never be stable",
925 cfg_fn!(rustc_attrs))),
926 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
928 "the `#[rustc_dirty]` attribute \
929 is just used for rustc unit tests \
930 and will never be stable",
931 cfg_fn!(rustc_attrs))),
932 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
934 "the `#[rustc_clean]` attribute \
935 is just used for rustc unit tests \
936 and will never be stable",
937 cfg_fn!(rustc_attrs))),
938 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
941 is just used for rustc unit tests \
942 and will never be stable",
943 cfg_fn!(rustc_attrs))),
944 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
947 is just used for rustc unit tests \
948 and will never be stable",
949 cfg_fn!(rustc_attrs))),
950 ("rustc_expected_cgu_reuse", Whitelisted, Gated(Stability::Unstable,
953 is just used for rustc unit tests \
954 and will never be stable",
955 cfg_fn!(rustc_attrs))),
956 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
959 is just used for rustc unit tests \
960 and will never be stable",
961 cfg_fn!(rustc_attrs))),
962 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
964 "internal rustc attributes will never be stable",
965 cfg_fn!(rustc_attrs))),
966 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
968 "internal rustc attributes will never be stable",
969 cfg_fn!(rustc_attrs))),
970 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
972 "the `#[rustc_mir]` attribute \
973 is just used for rustc unit tests \
974 and will never be stable",
975 cfg_fn!(rustc_attrs))),
976 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
978 "the `#[rustc_inherit_overflow_checks]` \
979 attribute is just used to control \
980 overflow checking behavior of several \
981 libcore functions that are inlined \
982 across crates and will never be stable",
983 cfg_fn!(rustc_attrs))),
985 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
987 "the `#[rustc_dump_program_clauses]` \
988 attribute is just used for rustc unit \
989 tests and will never be stable",
990 cfg_fn!(rustc_attrs))),
991 ("rustc_test_marker", Normal, Gated(Stability::Unstable,
993 "the `#[rustc_test_marker]` attribute \
994 is used internally to track tests",
995 cfg_fn!(rustc_attrs))),
996 ("rustc_transparent_macro", Whitelisted, Gated(Stability::Unstable,
998 "used internally for testing macro hygiene",
999 cfg_fn!(rustc_attrs))),
1002 ("nll", Whitelisted, Gated(Stability::Unstable,
1004 "Non lexical lifetimes",
1006 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
1007 "compiler_builtins",
1008 "the `#[compiler_builtins]` attribute is used to \
1009 identify the `compiler_builtins` crate which \
1010 contains compiler-rt intrinsics and will never be \
1012 cfg_fn!(compiler_builtins))),
1013 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
1014 "sanitizer_runtime",
1015 "the `#[sanitizer_runtime]` attribute is used to \
1016 identify crates that contain the runtime of a \
1017 sanitizer and will never be stable",
1018 cfg_fn!(sanitizer_runtime))),
1019 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
1021 "the `#[profiler_runtime]` attribute is used to \
1022 identify the `profiler_builtins` crate which \
1023 contains the profiler runtime and will never be \
1025 cfg_fn!(profiler_runtime))),
1027 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
1028 "allow_internal_unstable",
1029 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
1030 cfg_fn!(allow_internal_unstable))),
1032 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
1033 "allow_internal_unsafe",
1034 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
1035 cfg_fn!(allow_internal_unsafe))),
1037 ("fundamental", Whitelisted, Gated(Stability::Unstable,
1039 "the `#[fundamental]` attribute \
1040 is an experimental feature",
1041 cfg_fn!(fundamental))),
1043 ("proc_macro_derive", Normal, Ungated),
1045 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
1047 "internal implementation detail",
1048 cfg_fn!(rustc_attrs))),
1050 // FIXME: #14408 whitelist docs since rustdoc looks at them
1051 ("doc", Whitelisted, Ungated),
1053 // FIXME: #14406 these are processed in codegen, which happens after the
1055 ("cold", Whitelisted, Ungated),
1056 ("naked", Whitelisted, Gated(Stability::Unstable,
1058 "the `#[naked]` attribute \
1059 is an experimental feature",
1060 cfg_fn!(naked_functions))),
1061 ("target_feature", Whitelisted, Ungated),
1062 ("export_name", Whitelisted, Ungated),
1063 ("inline", Whitelisted, Ungated),
1064 ("link", Whitelisted, Ungated),
1065 ("link_name", Whitelisted, Ungated),
1066 ("link_section", Whitelisted, Ungated),
1067 ("no_builtins", Whitelisted, Ungated),
1068 ("no_mangle", Whitelisted, Ungated),
1069 ("no_debug", Whitelisted, Gated(
1070 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
1072 "the `#[no_debug]` attribute was an experimental feature that has been \
1073 deprecated due to lack of demand",
1074 cfg_fn!(no_debug))),
1075 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
1076 "omit_gdb_pretty_printer_section",
1077 "the `#[omit_gdb_pretty_printer_section]` \
1078 attribute is just used for the Rust test \
1080 cfg_fn!(omit_gdb_pretty_printer_section))),
1081 ("unsafe_destructor_blind_to_params",
1083 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761",
1084 Some("replace this attribute with `#[may_dangle]`")),
1085 "dropck_parametricity",
1086 "unsafe_destructor_blind_to_params has been replaced by \
1087 may_dangle and will be removed in the future",
1088 cfg_fn!(dropck_parametricity))),
1091 Gated(Stability::Unstable,
1093 "may_dangle has unstable semantics and may be removed in the future",
1094 cfg_fn!(dropck_eyepatch))),
1095 ("unwind", Whitelisted, Gated(Stability::Unstable,
1096 "unwind_attributes",
1097 "#[unwind] is experimental",
1098 cfg_fn!(unwind_attributes))),
1099 ("used", Whitelisted, Ungated),
1102 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1104 "`#[prelude_import]` is for use by rustc only",
1105 cfg_fn!(prelude_import))),
1107 // FIXME: #14407 these are only looked at on-demand so we can't
1108 // guarantee they'll have already been checked
1109 ("rustc_deprecated", Whitelisted, Ungated),
1110 ("must_use", Whitelisted, Ungated),
1111 ("stable", Whitelisted, Ungated),
1112 ("unstable", Whitelisted, Ungated),
1113 ("deprecated", Normal, Ungated),
1115 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1117 "unboxed_closures are still evolving",
1118 cfg_fn!(unboxed_closures))),
1120 ("windows_subsystem", Whitelisted, Ungated),
1122 ("proc_macro_attribute", Normal, Ungated),
1123 ("proc_macro", Normal, Ungated),
1125 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
1126 "rustc_derive_registrar",
1127 "used internally by rustc",
1128 cfg_fn!(rustc_attrs))),
1130 ("allow_fail", Normal, Gated(Stability::Unstable,
1132 "allow_fail attribute is currently unstable",
1133 cfg_fn!(allow_fail))),
1135 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1137 "this is an internal attribute that will \
1139 cfg_fn!(rustc_attrs))),
1141 // whitelists "identity-like" conversion methods to suggest on type mismatch
1142 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1144 "this is an internal attribute that will \
1146 cfg_fn!(rustc_attrs))),
1148 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1150 "never will be stable",
1151 cfg_fn!(rustc_attrs))),
1154 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1155 "infer_static_outlives_requirements",
1156 "infer 'static lifetime requirements",
1157 cfg_fn!(infer_static_outlives_requirements))),
1160 ("panic_handler", Normal, Ungated),
1162 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1163 "alloc_error_handler",
1164 "#[alloc_error_handler] is an unstable feature",
1165 cfg_fn!(alloc_error_handler))),
1167 // Crate level attributes
1168 ("crate_name", CrateLevel, Ungated),
1169 ("crate_type", CrateLevel, Ungated),
1170 ("crate_id", CrateLevel, Ungated),
1171 ("feature", CrateLevel, Ungated),
1172 ("no_start", CrateLevel, Ungated),
1173 ("no_main", CrateLevel, Ungated),
1174 ("no_builtins", CrateLevel, Ungated),
1175 ("recursion_limit", CrateLevel, Ungated),
1176 ("type_length_limit", CrateLevel, Ungated),
1177 ("test_runner", CrateLevel, Gated(Stability::Unstable,
1178 "custom_test_frameworks",
1179 EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
1180 cfg_fn!(custom_test_frameworks))),
1183 // cfg(...)'s that are feature gated
1184 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1185 // (name in cfg, feature, function to check if the feature is enabled)
1186 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1187 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1188 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1189 ("rustdoc", "doc_cfg", cfg_fn!(doc_cfg)),
1193 pub struct GatedCfg {
1199 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1200 let name = cfg.name().as_str();
1202 .position(|info| info.0 == name)
1211 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1212 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1213 if !has_feature(features) && !self.span.allows_unstable() {
1214 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1215 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1220 struct Context<'a> {
1221 features: &'a Features,
1222 parse_sess: &'a ParseSess,
1223 plugin_attributes: &'a [(String, AttributeType)],
1226 macro_rules! gate_feature_fn {
1227 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1228 let (cx, has_feature, span,
1229 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1230 let has_feature: bool = has_feature(&$cx.features);
1231 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1232 if !has_feature && !span.allows_unstable() {
1233 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1239 macro_rules! gate_feature {
1240 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1241 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1242 stringify!($feature), $explain, GateStrength::Hard)
1244 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1245 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1246 stringify!($feature), $explain, $level)
1250 impl<'a> Context<'a> {
1251 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1252 debug!("check_attribute(attr = {:?})", attr);
1253 let name = attr.name().as_str();
1254 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1256 if let Gated(_, name, desc, ref has_feature) = *gateage {
1257 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1258 } else if name == "doc" {
1259 if let Some(content) = attr.meta_item_list() {
1260 if content.iter().any(|c| c.check_name("include")) {
1261 gate_feature!(self, external_doc, attr.span,
1262 "#[doc(include = \"...\")] is experimental"
1267 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1271 for &(ref n, ref ty) in self.plugin_attributes {
1272 if attr.path == &**n {
1273 // Plugins can't gate attributes, so we don't check for it
1274 // unlike the code above; we only use this loop to
1275 // short-circuit to avoid the checks below
1276 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1280 if name.starts_with("rustc_") {
1281 gate_feature!(self, rustc_attrs, attr.span,
1282 "unless otherwise specified, attributes \
1283 with the prefix `rustc_` \
1284 are reserved for internal compiler diagnostics");
1285 } else if name.starts_with("derive_") {
1286 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1287 } else if !attr::is_known(attr) {
1288 // Only run the custom attribute lint during regular
1289 // feature gate checking. Macro gating runs
1290 // before the plugin attributes are registered
1291 // so we skip this then
1293 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1294 may have meaning added to it in the future", attr.path);
1295 gate_feature!(self, custom_attribute, attr.span, &msg);
1301 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1302 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1303 cx.check_attribute(attr, true);
1306 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1307 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1309 // FIXME (#28244): enforce that active features have issue numbers
1310 // assert!(issue.is_some())
1313 // search in Accepted, Removed, or Stable Removed features
1314 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1315 .find(|t| t.0 == feature);
1317 Some(&(_, _, issue, _)) => issue,
1318 None => panic!("Feature `{}` is not declared anywhere", feature),
1323 pub enum GateIssue {
1325 Library(Option<u32>)
1328 #[derive(Debug, Copy, Clone, PartialEq)]
1329 pub enum GateStrength {
1330 /// A hard error. (Most feature gates should use this.)
1332 /// Only a warning. (Use this only as backwards-compatibility demands.)
1336 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1338 feature_err(sess, feature, span, issue, explain).emit();
1341 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1342 explain: &str) -> DiagnosticBuilder<'a> {
1343 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1346 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1347 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1348 let diag = &sess.span_diagnostic;
1350 let issue = match issue {
1351 GateIssue::Language => find_lang_feature_issue(feature),
1352 GateIssue::Library(lib) => lib,
1355 let explanation = match issue {
1356 None | Some(0) => explain.to_owned(),
1357 Some(n) => format!("{} (see issue #{})", explain, n)
1360 let mut err = match level {
1361 GateStrength::Hard => {
1362 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1364 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1367 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1368 if sess.unstable_features.is_nightly_build() {
1369 err.help(&format!("add #![feature({})] to the \
1370 crate attributes to enable",
1374 // If we're on stable and only emitting a "soft" warning, add a note to
1375 // clarify that the feature isn't "on" (rather than being on but
1377 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1378 err.help("a nightly build of the compiler is required to enable this feature");
1385 const EXPLAIN_BOX_SYNTAX: &'static str =
1386 "box expression syntax is experimental; you can call `Box::new` instead.";
1388 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1389 "attributes on expressions are experimental.";
1391 pub const EXPLAIN_ASM: &'static str =
1392 "inline assembly is not stable enough for use and is subject to change";
1394 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1395 "`global_asm!` is not stable enough for use and is subject to change";
1397 pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &'static str =
1398 "custom test frameworks are an unstable feature";
1400 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1401 "`log_syntax!` is not stable enough for use and is subject to change";
1403 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1404 "`concat_idents` is not stable enough for use and is subject to change";
1406 pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
1407 "`format_args_nl` is only for internal language use and is subject to change";
1409 pub const EXPLAIN_TRACE_MACROS: &'static str =
1410 "`trace_macros` is not stable enough for use and is subject to change";
1411 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1412 "allow_internal_unstable side-steps feature gating and stability checks";
1413 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1414 "allow_internal_unsafe side-steps the unsafe_code lint";
1416 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1417 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1419 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1420 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1421 Prefer using procedural macro custom derive.";
1423 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1424 "attributes of the form `#[derive_*]` are reserved for the compiler";
1426 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1427 "unsized tuple coercion is not stable enough for use and is subject to change";
1429 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
1430 "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1432 struct PostExpansionVisitor<'a> {
1433 context: &'a Context<'a>,
1436 macro_rules! gate_feature_post {
1437 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1438 let (cx, span) = ($cx, $span);
1439 if !span.allows_unstable() {
1440 gate_feature!(cx.context, $feature, span, $explain)
1443 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1444 let (cx, span) = ($cx, $span);
1445 if !span.allows_unstable() {
1446 gate_feature!(cx.context, $feature, span, $explain, $level)
1451 impl<'a> PostExpansionVisitor<'a> {
1452 fn check_abi(&self, abi: Abi, span: Span) {
1454 Abi::RustIntrinsic => {
1455 gate_feature_post!(&self, intrinsics, span,
1456 "intrinsics are subject to change");
1458 Abi::PlatformIntrinsic => {
1459 gate_feature_post!(&self, platform_intrinsics, span,
1460 "platform intrinsics are experimental and possibly buggy");
1462 Abi::Vectorcall => {
1463 gate_feature_post!(&self, abi_vectorcall, span,
1464 "vectorcall is experimental and subject to change");
1467 gate_feature_post!(&self, abi_thiscall, span,
1468 "thiscall is experimental and subject to change");
1471 gate_feature_post!(&self, unboxed_closures, span,
1472 "rust-call ABI is subject to change");
1475 gate_feature_post!(&self, abi_ptx, span,
1476 "PTX ABIs are experimental and subject to change");
1478 Abi::Unadjusted => {
1479 gate_feature_post!(&self, abi_unadjusted, span,
1480 "unadjusted ABI is an implementation detail and perma-unstable");
1482 Abi::Msp430Interrupt => {
1483 gate_feature_post!(&self, abi_msp430_interrupt, span,
1484 "msp430-interrupt ABI is experimental and subject to change");
1486 Abi::X86Interrupt => {
1487 gate_feature_post!(&self, abi_x86_interrupt, span,
1488 "x86-interrupt ABI is experimental and subject to change");
1490 Abi::AmdGpuKernel => {
1491 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1492 "amdgpu-kernel ABI is experimental and subject to change");
1508 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1509 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1510 if !attr.span.allows_unstable() {
1511 // check for gated attributes
1512 self.context.check_attribute(attr, false);
1515 if attr.check_name("doc") {
1516 if let Some(content) = attr.meta_item_list() {
1517 if content.len() == 1 && content[0].check_name("cfg") {
1518 gate_feature_post!(&self, doc_cfg, attr.span,
1519 "#[doc(cfg(...))] is experimental"
1521 } else if content.iter().any(|c| c.check_name("masked")) {
1522 gate_feature_post!(&self, doc_masked, attr.span,
1523 "#[doc(masked)] is experimental"
1525 } else if content.iter().any(|c| c.check_name("spotlight")) {
1526 gate_feature_post!(&self, doc_spotlight, attr.span,
1527 "#[doc(spotlight)] is experimental"
1529 } else if content.iter().any(|c| c.check_name("alias")) {
1530 gate_feature_post!(&self, doc_alias, attr.span,
1531 "#[doc(alias = \"...\")] is experimental"
1533 } else if content.iter().any(|c| c.check_name("keyword")) {
1534 gate_feature_post!(&self, doc_keyword, attr.span,
1535 "#[doc(keyword = \"...\")] is experimental"
1541 if !self.context.features.unrestricted_attribute_tokens {
1542 // Unfortunately, `parse_meta` cannot be called speculatively
1543 // because it can report errors by itself, so we have to call it
1544 // only if the feature is disabled.
1545 if let Err(mut err) = attr.parse_meta(self.context.parse_sess) {
1546 err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
1551 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1552 if !name.as_str().is_ascii() {
1553 gate_feature_post!(&self,
1555 self.context.parse_sess.source_map().def_span(sp),
1556 "non-ascii idents are not fully supported.");
1560 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1561 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1562 if ident.name == "_" {
1563 gate_feature_post!(&self, underscore_imports, use_tree.span,
1564 "renaming imports with `_` is unstable");
1568 visit::walk_use_tree(self, use_tree, id);
1571 fn visit_item(&mut self, i: &'a ast::Item) {
1573 ast::ItemKind::ExternCrate(_) => {
1574 if i.ident.name == "_" {
1575 gate_feature_post!(&self, underscore_imports, i.span,
1576 "renaming extern crates with `_` is unstable");
1580 ast::ItemKind::Static(..) |
1581 ast::ItemKind::Const(_,_) => {
1582 if i.ident.name == "_" {
1583 gate_feature_post!(&self, underscore_const_names, i.span,
1584 "naming constants with `_` is unstable");
1588 ast::ItemKind::ForeignMod(ref foreign_module) => {
1589 self.check_abi(foreign_module.abi, i.span);
1592 ast::ItemKind::Fn(..) => {
1593 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1594 gate_feature_post!(&self, plugin_registrar, i.span,
1595 "compiler plugins are experimental and possibly buggy");
1597 if attr::contains_name(&i.attrs[..], "start") {
1598 gate_feature_post!(&self, start, i.span,
1599 "a #[start] function is an experimental \
1600 feature whose signature may change \
1603 if attr::contains_name(&i.attrs[..], "main") {
1604 gate_feature_post!(&self, main, i.span,
1605 "declaration of a nonstandard #[main] \
1606 function may change over time, for now \
1607 a top-level `fn main()` is required");
1611 ast::ItemKind::Struct(..) => {
1612 for attr in attr::filter_by_name(&i.attrs[..], "repr") {
1613 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1614 if item.check_name("simd") {
1615 gate_feature_post!(&self, repr_simd, attr.span,
1616 "SIMD types are experimental and possibly buggy");
1618 if let Some((name, _)) = item.name_value_literal() {
1619 if name == "packed" {
1620 gate_feature_post!(&self, repr_packed, attr.span,
1621 "the `#[repr(packed(n))]` attribute \
1629 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1630 if polarity == ast::ImplPolarity::Negative {
1631 gate_feature_post!(&self, optin_builtin_traits,
1633 "negative trait bounds are not yet fully implemented; \
1634 use marker types for now");
1637 if let ast::Defaultness::Default = defaultness {
1638 gate_feature_post!(&self, specialization,
1640 "specialization is unstable");
1644 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1645 gate_feature_post!(&self, optin_builtin_traits,
1647 "auto traits are experimental and possibly buggy");
1650 ast::ItemKind::TraitAlias(..) => {
1655 "trait aliases are experimental"
1659 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1660 let msg = "`macro` is experimental";
1661 gate_feature_post!(&self, decl_macro, i.span, msg);
1664 ast::ItemKind::Existential(..) => {
1669 "existential types are unstable"
1676 visit::walk_item(self, i);
1679 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1681 ast::ForeignItemKind::Fn(..) |
1682 ast::ForeignItemKind::Static(..) => {
1683 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1684 let links_to_llvm = match link_name {
1685 Some(val) => val.as_str().starts_with("llvm."),
1689 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1690 "linking to LLVM intrinsics is experimental");
1693 ast::ForeignItemKind::Ty => {
1694 gate_feature_post!(&self, extern_types, i.span,
1695 "extern types are experimental");
1697 ast::ForeignItemKind::Macro(..) => {}
1700 visit::walk_foreign_item(self, i)
1703 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1705 ast::TyKind::BareFn(ref bare_fn_ty) => {
1706 self.check_abi(bare_fn_ty.abi, ty.span);
1708 ast::TyKind::Never => {
1709 gate_feature_post!(&self, never_type, ty.span,
1710 "The `!` type is experimental");
1714 visit::walk_ty(self, ty)
1717 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1718 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1719 if let ast::TyKind::Never = output_ty.node {
1722 self.visit_ty(output_ty)
1727 fn visit_expr(&mut self, e: &'a ast::Expr) {
1729 ast::ExprKind::Box(_) => {
1730 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1732 ast::ExprKind::Type(..) => {
1733 gate_feature_post!(&self, type_ascription, e.span,
1734 "type ascription is experimental");
1736 ast::ExprKind::ObsoleteInPlace(..) => {
1737 // these get a hard error in ast-validation
1739 ast::ExprKind::Yield(..) => {
1740 gate_feature_post!(&self, generators,
1742 "yield syntax is experimental");
1744 ast::ExprKind::TryBlock(_) => {
1745 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
1747 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1749 gate_feature_post!(&self, if_while_or_patterns, e.span,
1750 "multiple patterns in `if let` and `while let` are unstable");
1753 ast::ExprKind::Block(_, opt_label) => {
1754 if let Some(label) = opt_label {
1755 gate_feature_post!(&self, label_break_value, label.ident.span,
1756 "labels on blocks are unstable");
1759 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1760 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1762 ast::ExprKind::Async(..) => {
1763 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1767 visit::walk_expr(self, e);
1770 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1771 visit::walk_arm(self, arm)
1774 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1775 match pattern.node {
1776 PatKind::Slice(_, Some(ref subslice), _) => {
1777 gate_feature_post!(&self, slice_patterns,
1779 "syntax for subslices in slice patterns is not yet stabilized");
1781 PatKind::Box(..) => {
1782 gate_feature_post!(&self, box_patterns,
1784 "box pattern syntax is experimental");
1786 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1787 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1788 "exclusive range pattern syntax is experimental");
1792 visit::walk_pat(self, pattern)
1795 fn visit_fn(&mut self,
1796 fn_kind: FnKind<'a>,
1797 fn_decl: &'a ast::FnDecl,
1801 FnKind::ItemFn(_, header, _, _) => {
1802 // check for const fn and async fn declarations
1803 if header.asyncness.is_async() {
1804 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1806 // stability of const fn methods are covered in
1807 // visit_trait_item and visit_impl_item below; this is
1808 // because default methods don't pass through this
1811 self.check_abi(header.abi, span);
1813 FnKind::Method(_, sig, _, _) => {
1814 self.check_abi(sig.header.abi, span);
1818 visit::walk_fn(self, fn_kind, fn_decl, span);
1821 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1823 ast::TraitItemKind::Method(ref sig, ref block) => {
1824 if block.is_none() {
1825 self.check_abi(sig.header.abi, ti.span);
1827 if sig.header.constness.node == ast::Constness::Const {
1828 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1831 ast::TraitItemKind::Type(_, ref default) => {
1832 // We use three if statements instead of something like match guards so that all
1833 // of these errors can be emitted if all cases apply.
1834 if default.is_some() {
1835 gate_feature_post!(&self, associated_type_defaults, ti.span,
1836 "associated type defaults are unstable");
1838 if !ti.generics.params.is_empty() {
1839 gate_feature_post!(&self, generic_associated_types, ti.span,
1840 "generic associated types are unstable");
1842 if !ti.generics.where_clause.predicates.is_empty() {
1843 gate_feature_post!(&self, generic_associated_types, ti.span,
1844 "where clauses on associated types are unstable");
1849 visit::walk_trait_item(self, ti);
1852 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1853 if ii.defaultness == ast::Defaultness::Default {
1854 gate_feature_post!(&self, specialization,
1856 "specialization is unstable");
1860 ast::ImplItemKind::Method(..) => {}
1861 ast::ImplItemKind::Existential(..) => {
1866 "existential types are unstable"
1869 ast::ImplItemKind::Type(_) => {
1870 if !ii.generics.params.is_empty() {
1871 gate_feature_post!(&self, generic_associated_types, ii.span,
1872 "generic associated types are unstable");
1874 if !ii.generics.where_clause.predicates.is_empty() {
1875 gate_feature_post!(&self, generic_associated_types, ii.span,
1876 "where clauses on associated types are unstable");
1881 visit::walk_impl_item(self, ii);
1884 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1885 for segment in &path.segments {
1886 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1887 // For such macros identifiers must have empty context, because this context is
1888 // used during name resolution and produced names must be unhygienic for compatibility.
1889 // On the other hand, we need the actual non-empty context for feature gate checking
1890 // because it's hygienic even for legacy macros. As previously stated, such context
1891 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1892 // there while keeping location info from the ident span.
1893 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1894 if segment.ident.name == keywords::Extern.name() {
1895 gate_feature_post!(&self, extern_in_paths, span,
1896 "`extern` in paths is experimental");
1900 visit::walk_path(self, path);
1903 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1904 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1905 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1906 "`crate` visibility modifier is experimental");
1908 visit::walk_vis(self, vis);
1912 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1913 crate_edition: Edition) -> Features {
1914 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1915 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1916 if let Some(reason) = reason {
1917 err.span_note(span, reason);
1922 // Some features are known to be incomplete and using them is likely to have
1923 // unanticipated results, such as compiler crashes. We warn the user about these
1925 let incomplete_features = ["generic_associated_types"];
1927 let mut features = Features::new();
1928 let mut edition_enabled_features = FxHashMap::default();
1930 for &edition in ALL_EDITIONS {
1931 if edition <= crate_edition {
1932 // The `crate_edition` implies its respective umbrella feature-gate
1933 // (i.e. `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
1934 edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
1938 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1939 if let Some(f_edition) = f_edition {
1940 if f_edition <= crate_edition {
1941 set(&mut features, DUMMY_SP);
1942 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1947 // Process the edition umbrella feature-gates first, to ensure
1948 // `edition_enabled_features` is completed before it's queried.
1949 for attr in krate_attrs {
1950 if !attr.check_name("feature") {
1954 let list = match attr.meta_item_list() {
1960 let name = if let Some(word) = mi.word() {
1966 if incomplete_features.iter().any(|f| *f == name.as_str()) {
1967 span_handler.struct_span_warn(
1970 "the feature `{}` is incomplete and may cause the compiler to crash",
1976 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1977 if *edition <= crate_edition {
1981 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1982 if let Some(f_edition) = f_edition {
1983 if f_edition <= *edition {
1984 // FIXME(Manishearth) there is currently no way to set
1985 // lib features by edition
1986 set(&mut features, DUMMY_SP);
1987 edition_enabled_features.insert(Symbol::intern(name), *edition);
1995 for attr in krate_attrs {
1996 if !attr.check_name("feature") {
2000 let list = match attr.meta_item_list() {
2003 span_err!(span_handler, attr.span, E0555,
2004 "malformed feature attribute, expected #![feature(...)]");
2010 let name = if let Some(word) = mi.word() {
2013 span_err!(span_handler, mi.span, E0556,
2014 "malformed feature, expected just one word");
2018 if let Some(edition) = edition_enabled_features.get(&name) {
2023 "the feature `{}` is included in the Rust {} edition",
2030 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
2031 // Handled in the separate loop above.
2035 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
2036 set(&mut features, mi.span);
2037 features.declared_lang_features.push((name, mi.span, None));
2041 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
2042 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
2043 if let Some((.., reason)) = removed.or(stable_removed) {
2044 feature_removed(span_handler, mi.span, *reason);
2048 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
2049 let since = Some(Symbol::intern(since));
2050 features.declared_lang_features.push((name, mi.span, since));
2054 features.declared_lib_features.push((name, mi.span));
2061 pub fn check_crate(krate: &ast::Crate,
2063 features: &Features,
2064 plugin_attributes: &[(String, AttributeType)],
2065 unstable: UnstableFeatures) {
2066 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2073 let visitor = &mut PostExpansionVisitor { context: &ctx };
2074 visit::walk_crate(visitor, krate);
2077 #[derive(Clone, Copy, Hash)]
2078 pub enum UnstableFeatures {
2079 /// Hard errors for unstable features are active, as on
2080 /// beta/stable channels.
2082 /// Allow features to be activated, as on nightly.
2084 /// Errors are bypassed for bootstrapping. This is required any time
2085 /// during the build that feature-related lints are set to warn or above
2086 /// because the build turns on warnings-as-errors and uses lots of unstable
2087 /// features. As a result, this is always required for building Rust itself.
2091 impl UnstableFeatures {
2092 pub fn from_environment() -> UnstableFeatures {
2093 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2094 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2095 // Whether we should enable unstable features for bootstrapping
2096 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2097 match (disable_unstable_features, bootstrap) {
2098 (_, true) => UnstableFeatures::Cheat,
2099 (true, _) => UnstableFeatures::Disallow,
2100 (false, _) => UnstableFeatures::Allow
2104 pub fn is_nightly_build(&self) -> bool {
2106 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2112 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2113 unstable: UnstableFeatures) {
2114 let allow_features = match unstable {
2115 UnstableFeatures::Allow => true,
2116 UnstableFeatures::Disallow => false,
2117 UnstableFeatures::Cheat => true
2119 if !allow_features {
2120 for attr in &krate.attrs {
2121 if attr.check_name("feature") {
2122 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2123 span_err!(span_handler, attr.span, E0554,
2124 "#![feature] may not be used on the {} release channel",