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(42219), 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(45388), 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(44660), None),
396 // Use `?` as the Kleene "at most one" operator
397 (active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
399 // Infer static outlives requirements; RFC 2093
400 (active, infer_static_outlives_requirements, "1.26.0", Some(44493), None),
402 // Multiple patterns with `|` in `if let` and `while let`
403 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
405 // Allows `#[repr(packed)]` attribute on structs
406 (active, repr_packed, "1.26.0", Some(33158), None),
408 // `use path as _;` and `extern crate c as _;`
409 (active, underscore_imports, "1.26.0", Some(48216), None),
411 // Allows macro invocations in `extern {}` blocks
412 (active, macros_in_extern, "1.27.0", Some(49476), None),
414 // `existential type`
415 (active, existential_type, "1.28.0", Some(34511), None),
417 // unstable #[target_feature] directives
418 (active, arm_target_feature, "1.27.0", Some(44839), None),
419 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
420 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
421 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
422 (active, mips_target_feature, "1.27.0", Some(44839), None),
423 (active, avx512_target_feature, "1.27.0", Some(44839), None),
424 (active, mmx_target_feature, "1.27.0", Some(44839), None),
425 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
426 (active, tbm_target_feature, "1.27.0", Some(44839), None),
427 (active, wasm_target_feature, "1.30.0", Some(44839), None),
429 // Allows macro invocations on modules expressions and statements and
430 // procedural macros to expand to non-items.
431 (active, proc_macro_hygiene, "1.30.0", Some(54727), None),
433 // #[doc(alias = "...")]
434 (active, doc_alias, "1.27.0", Some(50146), None),
436 // Allows irrefutable patterns in if-let and while-let statements (RFC 2086)
437 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
439 // Allows use of the :literal macro fragment specifier (RFC 1576)
440 (active, macro_literal_matcher, "1.27.0", Some(35625), None),
442 // inconsistent bounds in where clauses
443 (active, trivial_bounds, "1.28.0", Some(48214), None),
446 (active, label_break_value, "1.28.0", Some(48594), None),
448 // Integer match exhaustiveness checking
449 (active, exhaustive_integer_patterns, "1.30.0", Some(50907), None),
451 // RFC 2070: #[panic_implementation] / #[panic_handler]
452 (active, panic_implementation, "1.28.0", Some(44489), None),
454 // #[doc(keyword = "...")]
455 (active, doc_keyword, "1.28.0", Some(51315), None),
457 // Allows async and await syntax
458 (active, async_await, "1.28.0", Some(50547), None),
460 // #[alloc_error_handler]
461 (active, alloc_error_handler, "1.29.0", Some(51540), None),
463 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
465 // impl<I:Iterator> Iterator for &mut Iterator
466 // impl Debug for Foo<'_>
467 (active, impl_header_lifetime_elision, "1.30.0", Some(15872), Some(Edition::Edition2018)),
469 // Support for arbitrary delimited token streams in non-macro attributes
470 (active, unrestricted_attribute_tokens, "1.30.0", Some(44690), None),
472 // Allows `use x::y;` to resolve through `self::x`, not just `::x`
473 (active, uniform_paths, "1.30.0", Some(53130), None),
475 // Allows `Self` in type definitions
476 (active, self_in_typedefs, "1.30.0", Some(49303), None),
478 // Allows unsized rvalues at arguments and parameters
479 (active, unsized_locals, "1.30.0", Some(48055), None),
483 (active, custom_test_frameworks, "1.30.0", Some(50297), None),
485 // Non-builtin attributes in inner attribute position
486 (active, custom_inner_attributes, "1.30.0", Some(54726), None),
488 // Self struct constructor (RFC 2302)
489 (active, self_struct_ctor, "1.30.0", Some(51994), None),
491 // allow mixing of bind-by-move in patterns and references to
492 // those identifiers in guards, *if* we are using MIR-borrowck
493 // (aka NLL). Essentially this means you need to be on
494 // edition:2018 or later.
495 (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
497 // Allows `impl Trait` in bindings (`let`, `const`, `static`)
498 (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
500 // #[cfg_attr(predicate, multiple, attributes, here)]
501 (active, cfg_attr_multi, "1.31.0", Some(54881), None),
505 (removed, import_shadowing, "1.0.0", None, None, None),
506 (removed, managed_boxes, "1.0.0", None, None, None),
507 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
508 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
509 (removed, reflect, "1.0.0", Some(27749), None, None),
510 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
511 (removed, opt_out_copy, "1.0.0", None, None, None),
512 (removed, quad_precision_float, "1.0.0", None, None, None),
513 (removed, struct_inherit, "1.0.0", None, None, None),
514 (removed, test_removed_feature, "1.0.0", None, None, None),
515 (removed, visible_private_types, "1.0.0", None, None, None),
516 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
517 // Allows using items which are missing stability attributes
519 (removed, unmarked_api, "1.0.0", None, None, None),
520 (removed, pushpop_unsafe, "1.2.0", None, None, None),
521 (removed, allocator, "1.0.0", None, None, None),
522 (removed, simd, "1.0.0", Some(27731), None,
523 Some("removed in favor of `#[repr(simd)]`")),
524 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
525 Some("merged into `#![feature(slice_patterns)]`")),
526 (removed, macro_reexport, "1.0.0", Some(29638), None,
527 Some("subsumed by `pub use`")),
528 (removed, proc_macro_mod, "1.27.0", Some(54727), None,
529 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
530 (removed, proc_macro_expr, "1.27.0", Some(54727), None,
531 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
532 (removed, proc_macro_non_items, "1.27.0", Some(54727), None,
533 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
534 (removed, proc_macro_gen, "1.27.0", Some(54727), None,
535 Some("subsumed by `#![feature(proc_macro_hygiene)]`")),
539 (stable_removed, no_stack_check, "1.0.0", None, None),
543 (accepted, associated_types, "1.0.0", None, None),
544 // allow overloading augmented assignment operations like `a += b`
545 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
546 // allow empty structs and enum variants with braces
547 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
548 // Allows indexing into constant arrays.
549 (accepted, const_indexing, "1.26.0", Some(29947), None),
550 (accepted, default_type_params, "1.0.0", None, None),
551 (accepted, globs, "1.0.0", None, None),
552 (accepted, if_let, "1.0.0", None, None),
553 // A temporary feature gate used to enable parser extensions needed
554 // to bootstrap fix for #5723.
555 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
556 (accepted, macro_rules, "1.0.0", None, None),
557 // Allows using #![no_std]
558 (accepted, no_std, "1.6.0", None, None),
559 (accepted, slicing_syntax, "1.0.0", None, None),
560 (accepted, struct_variant, "1.0.0", None, None),
561 // These are used to test this portion of the compiler, they don't actually
563 (accepted, test_accepted_feature, "1.0.0", None, None),
564 (accepted, tuple_indexing, "1.0.0", None, None),
565 // Allows macros to appear in the type position.
566 (accepted, type_macros, "1.13.0", Some(27245), None),
567 (accepted, while_let, "1.0.0", None, None),
568 // Allows `#[deprecated]` attribute
569 (accepted, deprecated, "1.9.0", Some(29935), None),
571 (accepted, question_mark, "1.13.0", Some(31436), None),
572 // Allows `..` in tuple (struct) patterns
573 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
574 (accepted, item_like_imports, "1.15.0", Some(35120), None),
575 // Allows using `Self` and associated types in struct expressions and patterns.
576 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
577 // elide `'static` lifetimes in `static`s and `const`s
578 (accepted, static_in_const, "1.17.0", Some(35897), None),
579 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
580 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
581 // Allows the definition recursive static items.
582 (accepted, static_recursion, "1.17.0", Some(29719), None),
583 // pub(restricted) visibilities (RFC 1422)
584 (accepted, pub_restricted, "1.18.0", Some(32409), None),
585 // The #![windows_subsystem] attribute
586 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
587 // Allows `break {expr}` with a value inside `loop`s.
588 (accepted, loop_break_value, "1.19.0", Some(37339), None),
589 // Permits numeric fields in struct expressions and patterns.
590 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
591 // Coerces non capturing closures to function pointers
592 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
593 // Allows attributes on struct literal fields.
594 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
595 // Allows the definition of associated constants in `trait` or `impl`
597 (accepted, associated_consts, "1.20.0", Some(29646), None),
598 // Usage of the `compile_error!` macro
599 (accepted, compile_error, "1.20.0", Some(40872), None),
600 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
601 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
602 // Allow Drop types in constants (RFC 1440)
603 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
604 // Allows the sysV64 ABI to be specified on all platforms
605 // instead of just the platforms on which it is the C ABI
606 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
607 // Allows `repr(align(16))` struct attribute (RFC 1358)
608 (accepted, repr_align, "1.25.0", Some(33626), None),
609 // allow '|' at beginning of match arms (RFC 1925)
610 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
611 // Nested groups in `use` (RFC 2128)
612 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
614 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
615 // allow `..=` in patterns (RFC 1192)
616 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
617 // Termination trait in main (RFC 1937)
618 (accepted, termination_trait, "1.26.0", Some(43301), None),
619 // Copy/Clone closures (RFC 2132)
620 (accepted, clone_closures, "1.26.0", Some(44490), None),
621 (accepted, copy_closures, "1.26.0", Some(44490), None),
622 // Allows `impl Trait` in function arguments.
623 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
624 // Allows `impl Trait` in function return types.
625 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
627 (accepted, i128_type, "1.26.0", Some(35118), None),
628 // Default match binding modes (RFC 2005)
629 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
630 // allow `'_` placeholder lifetimes
631 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
632 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
633 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
634 // Allows cfg(target_feature = "...").
635 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
636 // Allows #[target_feature(...)]
637 (accepted, target_feature, "1.27.0", None, None),
638 // Trait object syntax with `dyn` prefix
639 (accepted, dyn_trait, "1.27.0", Some(44662), None),
640 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
641 (accepted, fn_must_use, "1.27.0", Some(43302), None),
642 // Allows use of the :lifetime macro fragment specifier
643 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
644 // Termination trait in tests (RFC 1937)
645 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
646 // The #[global_allocator] attribute
647 (accepted, global_allocator, "1.28.0", Some(27389), None),
648 // Allows `#[repr(transparent)]` attribute on newtype structs
649 (accepted, repr_transparent, "1.28.0", Some(43036), None),
650 // Defining procedural macros in `proc-macro` crates
651 (accepted, proc_macro, "1.29.0", Some(38356), None),
652 // `foo.rs` as an alternative to `foo/mod.rs`
653 (accepted, non_modrs_mods, "1.30.0", Some(44660), None),
654 // Allows use of the :vis macro fragment specifier
655 (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
656 // Allows importing and reexporting macros with `use`,
657 // enables macro modularization in general.
658 (accepted, use_extern_macros, "1.30.0", Some(35896), None),
659 // Allows keywords to be escaped for use as identifiers
660 (accepted, raw_identifiers, "1.30.0", Some(48589), None),
661 // Attributes scoped to tools
662 (accepted, tool_attributes, "1.30.0", Some(44690), None),
663 // Allows multi-segment paths in attributes and derives
664 (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
665 // Allows all literals in attribute lists and values of key-value pairs.
666 (accepted, attr_literals, "1.30.0", Some(34981), None),
667 // Infer outlives requirements; RFC 2093
668 (accepted, infer_outlives_requirements, "1.30.0", Some(44493), None),
669 (accepted, panic_handler, "1.30.0", Some(44489), None),
670 // Used to preserve symbols (see llvm.used)
671 (accepted, used, "1.30.0", Some(40289), None),
673 (accepted, crate_in_paths, "1.30.0", Some(45477), None),
674 // Resolve absolute paths as paths from other crates
675 (accepted, extern_absolute_paths, "1.30.0", Some(44660), None),
676 // Access to crate names passed via `--extern` through prelude
677 (accepted, extern_prelude, "1.30.0", Some(44660), None),
678 // Parentheses in patterns
679 (accepted, pattern_parentheses, "1.31.0", Some(51087), None),
680 // Allows the definition of `const fn` functions.
681 (accepted, min_const_fn, "1.31.0", Some(53555), None),
683 (accepted, tool_lints, "1.31.0", Some(44690), None),
686 // If you change this, please modify src/doc/unstable-book as well. You must
687 // move that documentation into the relevant place in the other docs, and
688 // remove the chapter on the flag.
690 #[derive(Copy, Clone, PartialEq, Debug)]
691 pub enum AttributeType {
692 /// Normal, builtin attribute that is consumed
693 /// by the compiler before the unused_attribute check
696 /// Builtin attribute that may not be consumed by the compiler
697 /// before the unused_attribute check. These attributes
698 /// will be ignored by the unused_attribute lint
701 /// Builtin attribute that is only allowed at the crate level
705 pub enum AttributeGate {
706 /// Is gated by a given feature gate, reason
707 /// and function to check if enabled
708 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
710 /// Ungated attribute, can be used on all release channels
715 fn is_deprecated(&self) -> bool {
717 Gated(Stability::Deprecated(_, _), ..) => true,
723 #[derive(Copy, Clone, Debug)]
726 // First argument is tracking issue link; second argument is an optional
727 // help message, which defaults to "remove this attribute"
728 Deprecated(&'static str, Option<&'static str>),
732 impl ::std::fmt::Debug for AttributeGate {
733 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
735 Gated(ref stab, name, expl, _) =>
736 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
737 Ungated => write!(fmt, "Ungated")
742 macro_rules! cfg_fn {
743 ($field: ident) => {{
744 fn f(features: &Features) -> bool {
747 f as fn(&Features) -> bool
751 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
752 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
755 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
756 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
759 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
760 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
763 // Attributes that have a special meaning to rustc or rustdoc
764 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
767 ("warn", Normal, Ungated),
768 ("allow", Normal, Ungated),
769 ("forbid", Normal, Ungated),
770 ("deny", Normal, Ungated),
772 ("macro_use", Normal, Ungated),
773 ("macro_export", Normal, Ungated),
774 ("plugin_registrar", Normal, Ungated),
776 ("cfg", Normal, Ungated),
777 ("cfg_attr", Normal, Ungated),
778 ("main", Normal, Ungated),
779 ("start", Normal, Ungated),
780 ("repr", Normal, Ungated),
781 ("path", Normal, Ungated),
782 ("abi", Normal, Ungated),
783 ("automatically_derived", Normal, Ungated),
784 ("no_mangle", Normal, Ungated),
785 ("no_link", Normal, Ungated),
786 ("derive", Normal, Ungated),
787 ("should_panic", Normal, Ungated),
788 ("ignore", Normal, Ungated),
789 ("no_implicit_prelude", Normal, Ungated),
790 ("reexport_test_harness_main", Normal, Ungated),
791 ("link_args", Normal, Gated(Stability::Unstable,
793 "the `link_args` attribute is experimental and not \
794 portable across platforms, it is recommended to \
795 use `#[link(name = \"foo\")] instead",
796 cfg_fn!(link_args))),
797 ("macro_escape", Normal, Ungated),
800 ("structural_match", Whitelisted, Gated(Stability::Unstable,
802 "the semantics of constant patterns is \
804 cfg_fn!(structural_match))),
807 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
809 "non exhaustive is an experimental feature",
810 cfg_fn!(non_exhaustive))),
813 ("marker", Normal, Gated(Stability::Unstable,
815 "marker traits is an experimental feature",
816 cfg_fn!(marker_trait_attr))),
818 ("plugin", CrateLevel, Gated(Stability::Unstable,
820 "compiler plugins are experimental \
824 ("no_std", CrateLevel, Ungated),
825 ("no_core", CrateLevel, Gated(Stability::Unstable,
827 "no_core is experimental",
829 ("lang", Normal, Gated(Stability::Unstable,
831 "language items are subject to change",
832 cfg_fn!(lang_items))),
833 ("linkage", Whitelisted, Gated(Stability::Unstable,
835 "the `linkage` attribute is experimental \
836 and not portable across platforms",
838 ("thread_local", Whitelisted, Gated(Stability::Unstable,
840 "`#[thread_local]` is an experimental feature, and does \
841 not currently handle destructors.",
842 cfg_fn!(thread_local))),
844 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
846 "the `#[rustc_on_unimplemented]` attribute \
847 is an experimental feature",
848 cfg_fn!(on_unimplemented))),
849 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
850 "rustc_const_unstable",
851 "the `#[rustc_const_unstable]` attribute \
852 is an internal feature",
853 cfg_fn!(rustc_const_unstable))),
854 ("global_allocator", Normal, Ungated),
855 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
856 "allocator_internals",
857 "the `#[default_lib_allocator]` \
858 attribute is an experimental feature",
859 cfg_fn!(allocator_internals))),
860 ("needs_allocator", Normal, Gated(Stability::Unstable,
861 "allocator_internals",
862 "the `#[needs_allocator]` \
863 attribute is an experimental \
865 cfg_fn!(allocator_internals))),
866 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
868 "the `#[panic_runtime]` attribute is \
869 an experimental feature",
870 cfg_fn!(panic_runtime))),
871 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
872 "needs_panic_runtime",
873 "the `#[needs_panic_runtime]` \
874 attribute is an experimental \
876 cfg_fn!(needs_panic_runtime))),
877 ("rustc_outlives", Normal, Gated(Stability::Unstable,
879 "the `#[rustc_outlives]` attribute \
880 is just used for rustc unit tests \
881 and will never be stable",
882 cfg_fn!(rustc_attrs))),
883 ("rustc_variance", Normal, Gated(Stability::Unstable,
885 "the `#[rustc_variance]` attribute \
886 is just used for rustc unit tests \
887 and will never be stable",
888 cfg_fn!(rustc_attrs))),
889 ("rustc_regions", Normal, Gated(Stability::Unstable,
891 "the `#[rustc_regions]` attribute \
892 is just used for rustc unit tests \
893 and will never be stable",
894 cfg_fn!(rustc_attrs))),
895 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
897 "the `#[rustc_error]` attribute \
898 is just used for rustc unit tests \
899 and will never be stable",
900 cfg_fn!(rustc_attrs))),
901 ("rustc_dump_user_substs", Whitelisted, Gated(Stability::Unstable,
904 is just used for rustc unit tests \
905 and will never be stable",
906 cfg_fn!(rustc_attrs))),
907 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
909 "the `#[rustc_if_this_changed]` attribute \
910 is just used for rustc unit tests \
911 and will never be stable",
912 cfg_fn!(rustc_attrs))),
913 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
915 "the `#[rustc_if_this_changed]` attribute \
916 is just used for rustc unit tests \
917 and will never be stable",
918 cfg_fn!(rustc_attrs))),
919 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
921 "the `#[rustc_dirty]` attribute \
922 is just used for rustc unit tests \
923 and will never be stable",
924 cfg_fn!(rustc_attrs))),
925 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
927 "the `#[rustc_clean]` attribute \
928 is just used for rustc unit tests \
929 and will never be stable",
930 cfg_fn!(rustc_attrs))),
931 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
934 is just used for rustc unit tests \
935 and will never be stable",
936 cfg_fn!(rustc_attrs))),
937 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
940 is just used for rustc unit tests \
941 and will never be stable",
942 cfg_fn!(rustc_attrs))),
943 ("rustc_expected_cgu_reuse", Whitelisted, Gated(Stability::Unstable,
946 is just used for rustc unit tests \
947 and will never be stable",
948 cfg_fn!(rustc_attrs))),
949 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
952 is just used for rustc unit tests \
953 and will never be stable",
954 cfg_fn!(rustc_attrs))),
955 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
957 "internal rustc attributes will never be stable",
958 cfg_fn!(rustc_attrs))),
959 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
961 "internal rustc attributes will never be stable",
962 cfg_fn!(rustc_attrs))),
963 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
965 "the `#[rustc_mir]` attribute \
966 is just used for rustc unit tests \
967 and will never be stable",
968 cfg_fn!(rustc_attrs))),
969 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
971 "the `#[rustc_inherit_overflow_checks]` \
972 attribute is just used to control \
973 overflow checking behavior of several \
974 libcore functions that are inlined \
975 across crates and will never be stable",
976 cfg_fn!(rustc_attrs))),
978 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
980 "the `#[rustc_dump_program_clauses]` \
981 attribute is just used for rustc unit \
982 tests and will never be stable",
983 cfg_fn!(rustc_attrs))),
984 ("rustc_test_marker", Normal, Gated(Stability::Unstable,
986 "the `#[rustc_test_marker]` attribute \
987 is used internally to track tests",
988 cfg_fn!(rustc_attrs))),
989 ("rustc_transparent_macro", Whitelisted, Gated(Stability::Unstable,
991 "used internally for testing macro hygiene",
992 cfg_fn!(rustc_attrs))),
995 ("nll", Whitelisted, Gated(Stability::Unstable,
997 "Non lexical lifetimes",
999 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
1000 "compiler_builtins",
1001 "the `#[compiler_builtins]` attribute is used to \
1002 identify the `compiler_builtins` crate which \
1003 contains compiler-rt intrinsics and will never be \
1005 cfg_fn!(compiler_builtins))),
1006 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
1007 "sanitizer_runtime",
1008 "the `#[sanitizer_runtime]` attribute is used to \
1009 identify crates that contain the runtime of a \
1010 sanitizer and will never be stable",
1011 cfg_fn!(sanitizer_runtime))),
1012 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
1014 "the `#[profiler_runtime]` attribute is used to \
1015 identify the `profiler_builtins` crate which \
1016 contains the profiler runtime and will never be \
1018 cfg_fn!(profiler_runtime))),
1020 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
1021 "allow_internal_unstable",
1022 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
1023 cfg_fn!(allow_internal_unstable))),
1025 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
1026 "allow_internal_unsafe",
1027 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
1028 cfg_fn!(allow_internal_unsafe))),
1030 ("fundamental", Whitelisted, Gated(Stability::Unstable,
1032 "the `#[fundamental]` attribute \
1033 is an experimental feature",
1034 cfg_fn!(fundamental))),
1036 ("proc_macro_derive", Normal, Ungated),
1038 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
1040 "internal implementation detail",
1041 cfg_fn!(rustc_attrs))),
1043 // FIXME: #14408 whitelist docs since rustdoc looks at them
1044 ("doc", Whitelisted, Ungated),
1046 // FIXME: #14406 these are processed in codegen, which happens after the
1048 ("cold", Whitelisted, Ungated),
1049 ("naked", Whitelisted, Gated(Stability::Unstable,
1051 "the `#[naked]` attribute \
1052 is an experimental feature",
1053 cfg_fn!(naked_functions))),
1054 ("target_feature", Whitelisted, Ungated),
1055 ("export_name", Whitelisted, Ungated),
1056 ("inline", Whitelisted, Ungated),
1057 ("link", Whitelisted, Ungated),
1058 ("link_name", Whitelisted, Ungated),
1059 ("link_section", Whitelisted, Ungated),
1060 ("no_builtins", Whitelisted, Ungated),
1061 ("no_mangle", Whitelisted, Ungated),
1062 ("no_debug", Whitelisted, Gated(
1063 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
1065 "the `#[no_debug]` attribute was an experimental feature that has been \
1066 deprecated due to lack of demand",
1067 cfg_fn!(no_debug))),
1068 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
1069 "omit_gdb_pretty_printer_section",
1070 "the `#[omit_gdb_pretty_printer_section]` \
1071 attribute is just used for the Rust test \
1073 cfg_fn!(omit_gdb_pretty_printer_section))),
1074 ("unsafe_destructor_blind_to_params",
1076 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761",
1077 Some("replace this attribute with `#[may_dangle]`")),
1078 "dropck_parametricity",
1079 "unsafe_destructor_blind_to_params has been replaced by \
1080 may_dangle and will be removed in the future",
1081 cfg_fn!(dropck_parametricity))),
1084 Gated(Stability::Unstable,
1086 "may_dangle has unstable semantics and may be removed in the future",
1087 cfg_fn!(dropck_eyepatch))),
1088 ("unwind", Whitelisted, Gated(Stability::Unstable,
1089 "unwind_attributes",
1090 "#[unwind] is experimental",
1091 cfg_fn!(unwind_attributes))),
1092 ("used", Whitelisted, Ungated),
1095 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1097 "`#[prelude_import]` is for use by rustc only",
1098 cfg_fn!(prelude_import))),
1100 // FIXME: #14407 these are only looked at on-demand so we can't
1101 // guarantee they'll have already been checked
1102 ("rustc_deprecated", Whitelisted, Ungated),
1103 ("must_use", Whitelisted, Ungated),
1104 ("stable", Whitelisted, Ungated),
1105 ("unstable", Whitelisted, Ungated),
1106 ("deprecated", Normal, Ungated),
1108 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1110 "unboxed_closures are still evolving",
1111 cfg_fn!(unboxed_closures))),
1113 ("windows_subsystem", Whitelisted, Ungated),
1115 ("proc_macro_attribute", Normal, Ungated),
1116 ("proc_macro", Normal, Ungated),
1118 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
1119 "rustc_derive_registrar",
1120 "used internally by rustc",
1121 cfg_fn!(rustc_attrs))),
1123 ("allow_fail", Normal, Gated(Stability::Unstable,
1125 "allow_fail attribute is currently unstable",
1126 cfg_fn!(allow_fail))),
1128 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1130 "this is an internal attribute that will \
1132 cfg_fn!(rustc_attrs))),
1134 // whitelists "identity-like" conversion methods to suggest on type mismatch
1135 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1137 "this is an internal attribute that will \
1139 cfg_fn!(rustc_attrs))),
1141 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1143 "never will be stable",
1144 cfg_fn!(rustc_attrs))),
1147 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1148 "infer_static_outlives_requirements",
1149 "infer 'static lifetime requirements",
1150 cfg_fn!(infer_static_outlives_requirements))),
1152 // RFC 2070 (deprecated attribute name)
1153 ("panic_implementation",
1155 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/44489\
1156 #issuecomment-415140224",
1157 Some("replace this attribute with `#[panic_handler]`")),
1158 "panic_implementation",
1159 "this attribute was renamed to `panic_handler`",
1160 cfg_fn!(panic_implementation))),
1163 ("panic_handler", Normal, Ungated),
1165 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1166 "alloc_error_handler",
1167 "#[alloc_error_handler] is an unstable feature",
1168 cfg_fn!(alloc_error_handler))),
1170 // Crate level attributes
1171 ("crate_name", CrateLevel, Ungated),
1172 ("crate_type", CrateLevel, Ungated),
1173 ("crate_id", CrateLevel, Ungated),
1174 ("feature", CrateLevel, Ungated),
1175 ("no_start", CrateLevel, Ungated),
1176 ("no_main", CrateLevel, Ungated),
1177 ("no_builtins", CrateLevel, Ungated),
1178 ("recursion_limit", CrateLevel, Ungated),
1179 ("type_length_limit", CrateLevel, Ungated),
1180 ("test_runner", CrateLevel, Gated(Stability::Unstable,
1181 "custom_test_frameworks",
1182 EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
1183 cfg_fn!(custom_test_frameworks))),
1186 // cfg(...)'s that are feature gated
1187 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1188 // (name in cfg, feature, function to check if the feature is enabled)
1189 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1190 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1191 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1192 ("rustdoc", "doc_cfg", cfg_fn!(doc_cfg)),
1196 pub struct GatedCfg {
1202 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1203 let name = cfg.name().as_str();
1205 .position(|info| info.0 == name)
1214 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1215 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1216 if !has_feature(features) && !self.span.allows_unstable() {
1217 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1218 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1223 struct Context<'a> {
1224 features: &'a Features,
1225 parse_sess: &'a ParseSess,
1226 plugin_attributes: &'a [(String, AttributeType)],
1229 macro_rules! gate_feature_fn {
1230 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1231 let (cx, has_feature, span,
1232 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1233 let has_feature: bool = has_feature(&$cx.features);
1234 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1235 if !has_feature && !span.allows_unstable() {
1236 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1242 macro_rules! gate_feature {
1243 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1244 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1245 stringify!($feature), $explain, GateStrength::Hard)
1247 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1248 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1249 stringify!($feature), $explain, $level)
1253 impl<'a> Context<'a> {
1254 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1255 debug!("check_attribute(attr = {:?})", attr);
1256 let name = attr.name().as_str();
1257 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1259 if let Gated(_, name, desc, ref has_feature) = *gateage {
1260 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1261 } else if name == "doc" {
1262 if let Some(content) = attr.meta_item_list() {
1263 if content.iter().any(|c| c.check_name("include")) {
1264 gate_feature!(self, external_doc, attr.span,
1265 "#[doc(include = \"...\")] is experimental"
1270 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1274 for &(ref n, ref ty) in self.plugin_attributes {
1275 if attr.path == &**n {
1276 // Plugins can't gate attributes, so we don't check for it
1277 // unlike the code above; we only use this loop to
1278 // short-circuit to avoid the checks below
1279 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1283 if name.starts_with("rustc_") {
1284 gate_feature!(self, rustc_attrs, attr.span,
1285 "unless otherwise specified, attributes \
1286 with the prefix `rustc_` \
1287 are reserved for internal compiler diagnostics");
1288 } else if name.starts_with("derive_") {
1289 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1290 } else if !attr::is_known(attr) {
1291 // Only run the custom attribute lint during regular
1292 // feature gate checking. Macro gating runs
1293 // before the plugin attributes are registered
1294 // so we skip this then
1296 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1297 may have meaning added to it in the future", attr.path);
1298 gate_feature!(self, custom_attribute, attr.span, &msg);
1304 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1305 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1306 cx.check_attribute(attr, true);
1309 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1310 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1312 // FIXME (#28244): enforce that active features have issue numbers
1313 // assert!(issue.is_some())
1316 // search in Accepted, Removed, or Stable Removed features
1317 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1318 .find(|t| t.0 == feature);
1320 Some(&(_, _, issue, _)) => issue,
1321 None => panic!("Feature `{}` is not declared anywhere", feature),
1326 pub enum GateIssue {
1328 Library(Option<u32>)
1331 #[derive(Debug, Copy, Clone, PartialEq)]
1332 pub enum GateStrength {
1333 /// A hard error. (Most feature gates should use this.)
1335 /// Only a warning. (Use this only as backwards-compatibility demands.)
1339 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1341 feature_err(sess, feature, span, issue, explain).emit();
1344 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1345 explain: &str) -> DiagnosticBuilder<'a> {
1346 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1349 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1350 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1351 let diag = &sess.span_diagnostic;
1353 let issue = match issue {
1354 GateIssue::Language => find_lang_feature_issue(feature),
1355 GateIssue::Library(lib) => lib,
1358 let explanation = match issue {
1359 None | Some(0) => explain.to_owned(),
1360 Some(n) => format!("{} (see issue #{})", explain, n)
1363 let mut err = match level {
1364 GateStrength::Hard => {
1365 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1367 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1370 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1371 if sess.unstable_features.is_nightly_build() {
1372 err.help(&format!("add #![feature({})] to the \
1373 crate attributes to enable",
1377 // If we're on stable and only emitting a "soft" warning, add a note to
1378 // clarify that the feature isn't "on" (rather than being on but
1380 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1381 err.help("a nightly build of the compiler is required to enable this feature");
1388 const EXPLAIN_BOX_SYNTAX: &'static str =
1389 "box expression syntax is experimental; you can call `Box::new` instead.";
1391 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1392 "attributes on expressions are experimental.";
1394 pub const EXPLAIN_ASM: &'static str =
1395 "inline assembly is not stable enough for use and is subject to change";
1397 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1398 "`global_asm!` is not stable enough for use and is subject to change";
1400 pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &'static str =
1401 "custom test frameworks are an unstable feature";
1403 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1404 "`log_syntax!` is not stable enough for use and is subject to change";
1406 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1407 "`concat_idents` is not stable enough for use and is subject to change";
1409 pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
1410 "`format_args_nl` is only for internal language use and is subject to change";
1412 pub const EXPLAIN_TRACE_MACROS: &'static str =
1413 "`trace_macros` is not stable enough for use and is subject to change";
1414 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1415 "allow_internal_unstable side-steps feature gating and stability checks";
1416 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1417 "allow_internal_unsafe side-steps the unsafe_code lint";
1419 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1420 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1422 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1423 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1424 Prefer using procedural macro custom derive.";
1426 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1427 "attributes of the form `#[derive_*]` are reserved for the compiler";
1429 pub const EXPLAIN_LITERAL_MATCHER: &'static str =
1430 ":literal fragment specifier is experimental and subject to change";
1432 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1433 "unsized tuple coercion is not stable enough for use and is subject to change";
1435 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
1436 "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1438 struct PostExpansionVisitor<'a> {
1439 context: &'a Context<'a>,
1442 macro_rules! gate_feature_post {
1443 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1444 let (cx, span) = ($cx, $span);
1445 if !span.allows_unstable() {
1446 gate_feature!(cx.context, $feature, span, $explain)
1449 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1450 let (cx, span) = ($cx, $span);
1451 if !span.allows_unstable() {
1452 gate_feature!(cx.context, $feature, span, $explain, $level)
1457 impl<'a> PostExpansionVisitor<'a> {
1458 fn check_abi(&self, abi: Abi, span: Span) {
1460 Abi::RustIntrinsic => {
1461 gate_feature_post!(&self, intrinsics, span,
1462 "intrinsics are subject to change");
1464 Abi::PlatformIntrinsic => {
1465 gate_feature_post!(&self, platform_intrinsics, span,
1466 "platform intrinsics are experimental and possibly buggy");
1468 Abi::Vectorcall => {
1469 gate_feature_post!(&self, abi_vectorcall, span,
1470 "vectorcall is experimental and subject to change");
1473 gate_feature_post!(&self, abi_thiscall, span,
1474 "thiscall is experimental and subject to change");
1477 gate_feature_post!(&self, unboxed_closures, span,
1478 "rust-call ABI is subject to change");
1481 gate_feature_post!(&self, abi_ptx, span,
1482 "PTX ABIs are experimental and subject to change");
1484 Abi::Unadjusted => {
1485 gate_feature_post!(&self, abi_unadjusted, span,
1486 "unadjusted ABI is an implementation detail and perma-unstable");
1488 Abi::Msp430Interrupt => {
1489 gate_feature_post!(&self, abi_msp430_interrupt, span,
1490 "msp430-interrupt ABI is experimental and subject to change");
1492 Abi::X86Interrupt => {
1493 gate_feature_post!(&self, abi_x86_interrupt, span,
1494 "x86-interrupt ABI is experimental and subject to change");
1496 Abi::AmdGpuKernel => {
1497 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1498 "amdgpu-kernel ABI is experimental and subject to change");
1514 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1515 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1516 if !attr.span.allows_unstable() {
1517 // check for gated attributes
1518 self.context.check_attribute(attr, false);
1521 if attr.check_name("doc") {
1522 if let Some(content) = attr.meta_item_list() {
1523 if content.len() == 1 && content[0].check_name("cfg") {
1524 gate_feature_post!(&self, doc_cfg, attr.span,
1525 "#[doc(cfg(...))] is experimental"
1527 } else if content.iter().any(|c| c.check_name("masked")) {
1528 gate_feature_post!(&self, doc_masked, attr.span,
1529 "#[doc(masked)] is experimental"
1531 } else if content.iter().any(|c| c.check_name("spotlight")) {
1532 gate_feature_post!(&self, doc_spotlight, attr.span,
1533 "#[doc(spotlight)] is experimental"
1535 } else if content.iter().any(|c| c.check_name("alias")) {
1536 gate_feature_post!(&self, doc_alias, attr.span,
1537 "#[doc(alias = \"...\")] is experimental"
1539 } else if content.iter().any(|c| c.check_name("keyword")) {
1540 gate_feature_post!(&self, doc_keyword, attr.span,
1541 "#[doc(keyword = \"...\")] is experimental"
1547 if !self.context.features.unrestricted_attribute_tokens {
1548 // Unfortunately, `parse_meta` cannot be called speculatively
1549 // because it can report errors by itself, so we have to call it
1550 // only if the feature is disabled.
1551 if let Err(mut err) = attr.parse_meta(self.context.parse_sess) {
1552 err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
1557 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1558 if !name.as_str().is_ascii() {
1559 gate_feature_post!(&self,
1561 self.context.parse_sess.source_map().def_span(sp),
1562 "non-ascii idents are not fully supported.");
1566 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1567 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1568 if ident.name == "_" {
1569 gate_feature_post!(&self, underscore_imports, use_tree.span,
1570 "renaming imports with `_` is unstable");
1574 visit::walk_use_tree(self, use_tree, id);
1577 fn visit_item(&mut self, i: &'a ast::Item) {
1579 ast::ItemKind::ExternCrate(_) => {
1580 if i.ident.name == "_" {
1581 gate_feature_post!(&self, underscore_imports, i.span,
1582 "renaming extern crates 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 if let Some(attr) = attr::find_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::TraitAlias(..) => {
1628 gate_feature_post!(&self, trait_alias,
1630 "trait aliases are not yet fully implemented");
1633 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1634 if polarity == ast::ImplPolarity::Negative {
1635 gate_feature_post!(&self, optin_builtin_traits,
1637 "negative trait bounds are not yet fully implemented; \
1638 use marker types for now");
1641 if let ast::Defaultness::Default = defaultness {
1642 gate_feature_post!(&self, specialization,
1644 "specialization is unstable");
1648 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1649 gate_feature_post!(&self, optin_builtin_traits,
1651 "auto traits are experimental and possibly buggy");
1654 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1655 let msg = "`macro` is experimental";
1656 gate_feature_post!(&self, decl_macro, i.span, msg);
1659 ast::ItemKind::Existential(..) => {
1664 "existential types are unstable"
1671 visit::walk_item(self, i);
1674 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1676 ast::ForeignItemKind::Fn(..) |
1677 ast::ForeignItemKind::Static(..) => {
1678 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1679 let links_to_llvm = match link_name {
1680 Some(val) => val.as_str().starts_with("llvm."),
1684 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1685 "linking to LLVM intrinsics is experimental");
1688 ast::ForeignItemKind::Ty => {
1689 gate_feature_post!(&self, extern_types, i.span,
1690 "extern types are experimental");
1692 ast::ForeignItemKind::Macro(..) => {}
1695 visit::walk_foreign_item(self, i)
1698 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1700 ast::TyKind::BareFn(ref bare_fn_ty) => {
1701 self.check_abi(bare_fn_ty.abi, ty.span);
1703 ast::TyKind::Never => {
1704 gate_feature_post!(&self, never_type, ty.span,
1705 "The `!` type is experimental");
1709 visit::walk_ty(self, ty)
1712 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1713 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1714 if let ast::TyKind::Never = output_ty.node {
1717 self.visit_ty(output_ty)
1722 fn visit_expr(&mut self, e: &'a ast::Expr) {
1724 ast::ExprKind::Box(_) => {
1725 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1727 ast::ExprKind::Type(..) => {
1728 gate_feature_post!(&self, type_ascription, e.span,
1729 "type ascription is experimental");
1731 ast::ExprKind::ObsoleteInPlace(..) => {
1732 // these get a hard error in ast-validation
1734 ast::ExprKind::Yield(..) => {
1735 gate_feature_post!(&self, generators,
1737 "yield syntax is experimental");
1739 ast::ExprKind::TryBlock(_) => {
1740 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
1742 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1744 gate_feature_post!(&self, if_while_or_patterns, e.span,
1745 "multiple patterns in `if let` and `while let` are unstable");
1748 ast::ExprKind::Block(_, opt_label) => {
1749 if let Some(label) = opt_label {
1750 gate_feature_post!(&self, label_break_value, label.ident.span,
1751 "labels on blocks are unstable");
1754 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1755 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1757 ast::ExprKind::Async(..) => {
1758 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1762 visit::walk_expr(self, e);
1765 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1766 visit::walk_arm(self, arm)
1769 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1770 match pattern.node {
1771 PatKind::Slice(_, Some(ref subslice), _) => {
1772 gate_feature_post!(&self, slice_patterns,
1774 "syntax for subslices in slice patterns is not yet stabilized");
1776 PatKind::Box(..) => {
1777 gate_feature_post!(&self, box_patterns,
1779 "box pattern syntax is experimental");
1781 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1782 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1783 "exclusive range pattern syntax is experimental");
1787 visit::walk_pat(self, pattern)
1790 fn visit_fn(&mut self,
1791 fn_kind: FnKind<'a>,
1792 fn_decl: &'a ast::FnDecl,
1796 FnKind::ItemFn(_, header, _, _) => {
1797 // check for const fn and async fn declarations
1798 if header.asyncness.is_async() {
1799 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1801 // stability of const fn methods are covered in
1802 // visit_trait_item and visit_impl_item below; this is
1803 // because default methods don't pass through this
1806 self.check_abi(header.abi, span);
1808 FnKind::Method(_, sig, _, _) => {
1809 self.check_abi(sig.header.abi, span);
1813 visit::walk_fn(self, fn_kind, fn_decl, span);
1816 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1818 ast::TraitItemKind::Method(ref sig, ref block) => {
1819 if block.is_none() {
1820 self.check_abi(sig.header.abi, ti.span);
1822 if sig.header.constness.node == ast::Constness::Const {
1823 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1826 ast::TraitItemKind::Type(_, ref default) => {
1827 // We use three if statements instead of something like match guards so that all
1828 // of these errors can be emitted if all cases apply.
1829 if default.is_some() {
1830 gate_feature_post!(&self, associated_type_defaults, ti.span,
1831 "associated type defaults are unstable");
1833 if !ti.generics.params.is_empty() {
1834 gate_feature_post!(&self, generic_associated_types, ti.span,
1835 "generic associated types are unstable");
1837 if !ti.generics.where_clause.predicates.is_empty() {
1838 gate_feature_post!(&self, generic_associated_types, ti.span,
1839 "where clauses on associated types are unstable");
1844 visit::walk_trait_item(self, ti);
1847 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1848 if ii.defaultness == ast::Defaultness::Default {
1849 gate_feature_post!(&self, specialization,
1851 "specialization is unstable");
1855 ast::ImplItemKind::Method(..) => {}
1856 ast::ImplItemKind::Existential(..) => {
1861 "existential types are unstable"
1864 ast::ImplItemKind::Type(_) => {
1865 if !ii.generics.params.is_empty() {
1866 gate_feature_post!(&self, generic_associated_types, ii.span,
1867 "generic associated types are unstable");
1869 if !ii.generics.where_clause.predicates.is_empty() {
1870 gate_feature_post!(&self, generic_associated_types, ii.span,
1871 "where clauses on associated types are unstable");
1876 visit::walk_impl_item(self, ii);
1879 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1880 for segment in &path.segments {
1881 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1882 // For such macros identifiers must have empty context, because this context is
1883 // used during name resolution and produced names must be unhygienic for compatibility.
1884 // On the other hand, we need the actual non-empty context for feature gate checking
1885 // because it's hygienic even for legacy macros. As previously stated, such context
1886 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1887 // there while keeping location info from the ident span.
1888 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1889 if segment.ident.name == keywords::Extern.name() {
1890 gate_feature_post!(&self, extern_in_paths, span,
1891 "`extern` in paths is experimental");
1895 visit::walk_path(self, path);
1898 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1899 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1900 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1901 "`crate` visibility modifier is experimental");
1903 visit::walk_vis(self, vis);
1907 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1908 crate_edition: Edition) -> Features {
1909 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1910 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1911 if let Some(reason) = reason {
1912 err.span_note(span, reason);
1917 // Some features are known to be incomplete and using them is likely to have
1918 // unanticipated results, such as compiler crashes. We warn the user about these
1920 let incomplete_features = ["generic_associated_types"];
1922 let mut features = Features::new();
1923 let mut edition_enabled_features = FxHashMap();
1925 for &edition in ALL_EDITIONS {
1926 if edition <= crate_edition {
1927 // The `crate_edition` implies its respective umbrella feature-gate
1928 // (i.e. `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
1929 edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
1933 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1934 if let Some(f_edition) = f_edition {
1935 if f_edition <= crate_edition {
1936 set(&mut features, DUMMY_SP);
1937 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1942 // Process the edition umbrella feature-gates first, to ensure
1943 // `edition_enabled_features` is completed before it's queried.
1944 for attr in krate_attrs {
1945 if !attr.check_name("feature") {
1949 let list = match attr.meta_item_list() {
1955 let name = if let Some(word) = mi.word() {
1961 if incomplete_features.iter().any(|f| *f == name.as_str()) {
1962 span_handler.struct_span_warn(
1965 "the feature `{}` is incomplete and may cause the compiler to crash",
1971 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1972 if *edition <= crate_edition {
1976 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1977 if let Some(f_edition) = f_edition {
1978 if f_edition <= *edition {
1979 // FIXME(Manishearth) there is currently no way to set
1980 // lib features by edition
1981 set(&mut features, DUMMY_SP);
1982 edition_enabled_features.insert(Symbol::intern(name), *edition);
1990 for attr in krate_attrs {
1991 if !attr.check_name("feature") {
1995 let list = match attr.meta_item_list() {
1998 span_err!(span_handler, attr.span, E0555,
1999 "malformed feature attribute, expected #![feature(...)]");
2005 let name = if let Some(word) = mi.word() {
2008 span_err!(span_handler, mi.span, E0556,
2009 "malformed feature, expected just one word");
2013 if let Some(edition) = edition_enabled_features.get(&name) {
2018 "the feature `{}` is included in the Rust {} edition",
2025 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
2026 // Handled in the separate loop above.
2030 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
2031 set(&mut features, mi.span);
2032 features.declared_lang_features.push((name, mi.span, None));
2036 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
2037 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
2038 if let Some((.., reason)) = removed.or(stable_removed) {
2039 feature_removed(span_handler, mi.span, *reason);
2043 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
2044 let since = Some(Symbol::intern(since));
2045 features.declared_lang_features.push((name, mi.span, since));
2049 features.declared_lib_features.push((name, mi.span));
2056 pub fn check_crate(krate: &ast::Crate,
2058 features: &Features,
2059 plugin_attributes: &[(String, AttributeType)],
2060 unstable: UnstableFeatures) {
2061 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2068 let visitor = &mut PostExpansionVisitor { context: &ctx };
2069 visit::walk_crate(visitor, krate);
2072 #[derive(Clone, Copy, Hash)]
2073 pub enum UnstableFeatures {
2074 /// Hard errors for unstable features are active, as on
2075 /// beta/stable channels.
2077 /// Allow features to be activated, as on nightly.
2079 /// Errors are bypassed for bootstrapping. This is required any time
2080 /// during the build that feature-related lints are set to warn or above
2081 /// because the build turns on warnings-as-errors and uses lots of unstable
2082 /// features. As a result, this is always required for building Rust itself.
2086 impl UnstableFeatures {
2087 pub fn from_environment() -> UnstableFeatures {
2088 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2089 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2090 // Whether we should enable unstable features for bootstrapping
2091 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2092 match (disable_unstable_features, bootstrap) {
2093 (_, true) => UnstableFeatures::Cheat,
2094 (true, _) => UnstableFeatures::Disallow,
2095 (false, _) => UnstableFeatures::Allow
2099 pub fn is_nightly_build(&self) -> bool {
2101 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2107 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2108 unstable: UnstableFeatures) {
2109 let allow_features = match unstable {
2110 UnstableFeatures::Allow => true,
2111 UnstableFeatures::Disallow => false,
2112 UnstableFeatures::Cheat => true
2114 if !allow_features {
2115 for attr in &krate.attrs {
2116 if attr.check_name("feature") {
2117 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2118 span_err!(span_handler, attr.span, E0554,
2119 "#![feature] may not be used on the {} release channel",