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};
43 // The const_fn feature also enables the min_const_fn feature, because `min_const_fn` allows
44 // the declaration `const fn`, but the `const_fn` feature gate enables things inside those
45 // functions that we do not want to expose to the user for now.
47 fn f(features: &mut Features, _: Span) {
48 features.const_fn = true;
49 features.min_const_fn = true;
51 f as fn(&mut Features, Span)
54 fn f(features: &mut Features, _: Span) {
55 features.$field = true;
57 f as fn(&mut Features, Span)
61 macro_rules! declare_features {
62 ($((active, $feature: ident, $ver: expr, $issue: expr, $edition: expr),)+) => {
63 /// Represents active features that are currently being implemented or
64 /// currently being considered for addition/removal.
65 const ACTIVE_FEATURES:
66 &'static [(&'static str, &'static str, Option<u32>,
67 Option<Edition>, fn(&mut Features, Span))] =
68 &[$((stringify!($feature), $ver, $issue, $edition, set!($feature))),+];
70 /// A set of features to be used by later passes.
73 /// `#![feature]` attrs for language features, for error reporting
74 pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
75 /// `#![feature]` attrs for non-language (library) features
76 pub declared_lib_features: Vec<(Symbol, Span)>,
77 $(pub $feature: bool),+
81 pub fn new() -> Features {
83 declared_lang_features: Vec::new(),
84 declared_lib_features: Vec::new(),
89 pub fn walk_feature_fields<F>(&self, mut f: F)
90 where F: FnMut(&str, bool)
92 $(f(stringify!($feature), self.$feature);)+
97 ($((removed, $feature: ident, $ver: expr, $issue: expr, None, $reason: expr),)+) => {
98 /// Represents unstable features which have since been removed (it was once Active)
99 const REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
100 $((stringify!($feature), $ver, $issue, $reason)),+
104 ($((stable_removed, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
105 /// Represents stable features which have since been removed (it was once Accepted)
106 const STABLE_REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
107 $((stringify!($feature), $ver, $issue, None)),+
111 ($((accepted, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
112 /// Those language feature has since been Accepted (it was once Active)
113 const ACCEPTED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
114 $((stringify!($feature), $ver, $issue, None)),+
119 // If you change this, please modify src/doc/unstable-book as well.
121 // Don't ever remove anything from this list; set them to 'Removed'.
123 // The version numbers here correspond to the version in which the current status
124 // was set. This is most important for knowing when a particular feature became
127 // NB: tools/tidy/src/features.rs parses this information directly out of the
128 // source, so take care when modifying it.
131 (active, asm, "1.0.0", Some(29722), None),
132 (active, concat_idents, "1.0.0", Some(29599), None),
133 (active, link_args, "1.0.0", Some(29596), None),
134 (active, log_syntax, "1.0.0", Some(29598), None),
135 (active, non_ascii_idents, "1.0.0", Some(28979), None),
136 (active, plugin_registrar, "1.0.0", Some(29597), None),
137 (active, thread_local, "1.0.0", Some(29594), None),
138 (active, trace_macros, "1.0.0", Some(29598), None),
140 // rustc internal, for now
141 (active, intrinsics, "1.0.0", None, None),
142 (active, lang_items, "1.0.0", None, None),
143 (active, format_args_nl, "1.29.0", None, None),
145 (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
146 (active, linkage, "1.0.0", Some(29603), None),
147 (active, quote, "1.0.0", Some(29601), None),
150 (active, rustc_diagnostic_macros, "1.0.0", None, None),
151 (active, rustc_const_unstable, "1.0.0", None, None),
152 (active, box_syntax, "1.0.0", Some(49733), None),
153 (active, unboxed_closures, "1.0.0", Some(29625), None),
155 (active, fundamental, "1.0.0", Some(29635), None),
156 (active, main, "1.0.0", Some(29634), None),
157 (active, needs_allocator, "1.4.0", Some(27389), None),
158 (active, on_unimplemented, "1.0.0", Some(29628), None),
159 (active, plugin, "1.0.0", Some(29597), None),
160 (active, simd_ffi, "1.0.0", Some(27731), None),
161 (active, start, "1.0.0", Some(29633), None),
162 (active, structural_match, "1.8.0", Some(31434), None),
163 (active, panic_runtime, "1.10.0", Some(32837), None),
164 (active, needs_panic_runtime, "1.10.0", Some(32837), None),
166 // OIBIT specific features
167 (active, optin_builtin_traits, "1.0.0", Some(13231), None),
169 // Allows use of #[staged_api]
172 (active, staged_api, "1.0.0", None, None),
174 // Allows using #![no_core]
175 (active, no_core, "1.3.0", Some(29639), None),
177 // Allows using `box` in patterns; RFC 469
178 (active, box_patterns, "1.0.0", Some(29641), None),
180 // Allows using the unsafe_destructor_blind_to_params attribute;
182 (active, dropck_parametricity, "1.3.0", Some(28498), None),
184 // Allows using the may_dangle attribute; RFC 1327
185 (active, dropck_eyepatch, "1.10.0", Some(34761), None),
187 // Allows the use of custom attributes; RFC 572
188 (active, custom_attribute, "1.0.0", Some(29642), None),
190 // Allows the use of #[derive(Anything)] as sugar for
191 // #[derive_Anything].
192 (active, custom_derive, "1.0.0", Some(29644), None),
194 // Allows the use of rustc_* attributes; RFC 572
195 (active, rustc_attrs, "1.0.0", Some(29642), None),
197 // Allows the use of non lexical lifetimes; RFC 2094
198 (active, nll, "1.0.0", Some(43234), None),
200 // Allows the use of #[allow_internal_unstable]. This is an
201 // attribute on macro_rules! and can't use the attribute handling
202 // below (it has to be checked before expansion possibly makes
203 // macros disappear).
206 (active, allow_internal_unstable, "1.0.0", None, None),
208 // Allows the use of #[allow_internal_unsafe]. This is an
209 // attribute on macro_rules! and can't use the attribute handling
210 // below (it has to be checked before expansion possibly makes
211 // macros disappear).
214 (active, allow_internal_unsafe, "1.0.0", None, None),
216 // #23121. Array patterns have some hazards yet.
217 (active, slice_patterns, "1.0.0", Some(23121), None),
219 // Allows the definition of `const fn` functions with some advanced features.
220 (active, const_fn, "1.2.0", Some(24111), None),
222 // Allows the definition of `const fn` functions.
223 (active, min_const_fn, "1.30.0", Some(53555), None),
225 // Allows let bindings and destructuring in `const fn` functions and constants.
226 (active, const_let, "1.22.1", Some(48821), None),
228 // Allows accessing fields of unions inside const fn.
229 (active, const_fn_union, "1.27.0", Some(51909), None),
231 // Allows casting raw pointers to `usize` during const eval.
232 (active, const_raw_ptr_to_usize_cast, "1.27.0", Some(51910), None),
234 // Allows dereferencing raw pointers during const eval.
235 (active, const_raw_ptr_deref, "1.27.0", Some(51911), None),
237 // Allows reinterpretation of the bits of a value of one type as another type during const eval.
238 (active, const_transmute, "1.29.0", Some(53605), None),
240 // Allows comparing raw pointers during const eval.
241 (active, const_compare_raw_pointers, "1.27.0", Some(53020), None),
243 // Allows panicking during const eval (produces compile-time errors)
244 (active, const_panic, "1.30.0", Some(51999), None),
246 // Allows using #[prelude_import] on glob `use` items.
249 (active, prelude_import, "1.2.0", None, None),
251 // Allows default type parameters to influence type inference.
252 (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
254 // Allows associated type defaults
255 (active, associated_type_defaults, "1.2.0", Some(29661), None),
257 // Allows `repr(simd)`, and importing the various simd intrinsics
258 (active, repr_simd, "1.4.0", Some(27731), None),
260 // Allows `extern "platform-intrinsic" { ... }`
261 (active, platform_intrinsics, "1.4.0", Some(27731), None),
263 // Allows `#[unwind(..)]`
264 // rustc internal for rust runtime
265 (active, unwind_attributes, "1.4.0", None, None),
267 // Allows the use of `#[naked]` on functions.
268 (active, naked_functions, "1.9.0", Some(32408), None),
270 // Allows `#[no_debug]`
271 (active, no_debug, "1.5.0", Some(29721), None),
273 // Allows `#[omit_gdb_pretty_printer_section]`
276 (active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
278 // Allows cfg(target_vendor = "...").
279 (active, cfg_target_vendor, "1.5.0", Some(29718), None),
281 // Allow attributes on expressions and non-item statements
282 (active, stmt_expr_attributes, "1.6.0", Some(15701), None),
284 // allow using type ascription in expressions
285 (active, type_ascription, "1.6.0", Some(23416), None),
287 // Allows cfg(target_thread_local)
288 (active, cfg_target_thread_local, "1.7.0", Some(29594), None),
291 (active, abi_vectorcall, "1.7.0", None, None),
294 (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
296 // impl specialization (RFC 1210)
297 (active, specialization, "1.7.0", Some(31844), None),
299 // Allows cfg(target_has_atomic = "...").
300 (active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
302 // The `!` type. Does not imply exhaustive_patterns (below) any more.
303 (active, never_type, "1.13.0", Some(35121), None),
305 // Allows exhaustive pattern matching on types that contain uninhabited types
306 (active, exhaustive_patterns, "1.13.0", Some(51085), None),
308 // Allows untagged unions `union U { ... }`
309 (active, untagged_unions, "1.13.0", Some(32836), None),
311 // Used to identify the `compiler_builtins` crate
313 (active, compiler_builtins, "1.13.0", None, None),
315 // Allows #[link(..., cfg(..))]
316 (active, link_cfg, "1.14.0", Some(37406), None),
318 // `extern "ptx-*" fn()`
319 (active, abi_ptx, "1.15.0", Some(38788), None),
321 // The `repr(i128)` annotation for enums
322 (active, repr128, "1.16.0", Some(35118), None),
324 // The `unadjusted` ABI. Perma unstable.
326 (active, abi_unadjusted, "1.16.0", None, None),
328 // Declarative macros 2.0 (`macro`).
329 (active, decl_macro, "1.17.0", Some(39412), None),
331 // Allows #[link(kind="static-nobundle"...)]
332 (active, static_nobundle, "1.16.0", Some(37403), None),
334 // `extern "msp430-interrupt" fn()`
335 (active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
337 // Used to identify crates that contain sanitizer runtimes
339 (active, sanitizer_runtime, "1.17.0", None, None),
341 // Used to identify crates that contain the profiler runtime
344 (active, profiler_runtime, "1.18.0", None, None),
346 // `extern "x86-interrupt" fn()`
347 (active, abi_x86_interrupt, "1.17.0", Some(40180), None),
349 // Allows the `try {...}` expression
350 (active, try_blocks, "1.29.0", Some(31436), None),
352 // Used to preserve symbols (see llvm.used)
353 (active, used, "1.18.0", Some(40289), None),
355 // Allows module-level inline assembly by way of global_asm!()
356 (active, global_asm, "1.18.0", Some(35119), None),
358 // Allows overlapping impls of marker traits
359 (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
362 (active, abi_thiscall, "1.19.0", None, None),
364 // Allows a test to fail without failing the whole suite
365 (active, allow_fail, "1.19.0", Some(42219), None),
367 // Allows unsized tuple coercion.
368 (active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
371 (active, generators, "1.21.0", Some(43122), None),
374 (active, trait_alias, "1.24.0", Some(41517), None),
377 (active, allocator_internals, "1.20.0", None, None),
380 (active, doc_cfg, "1.21.0", Some(43781), None),
382 (active, doc_masked, "1.21.0", Some(44027), None),
384 (active, doc_spotlight, "1.22.0", Some(45040), None),
385 // #[doc(include="some-file")]
386 (active, external_doc, "1.22.0", Some(44732), None),
388 // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
389 (active, non_exhaustive, "1.22.0", Some(44109), None),
391 // `crate` as visibility modifier, synonymous to `pub(crate)`
392 (active, crate_visibility_modifier, "1.23.0", Some(45388), Some(Edition::Edition2018)),
395 (active, extern_types, "1.23.0", Some(43467), None),
397 // Allows trait methods with arbitrary self types
398 (active, arbitrary_self_types, "1.23.0", Some(44874), None),
401 (active, crate_in_paths, "1.23.0", Some(45477), Some(Edition::Edition2018)),
403 // In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
404 (active, in_band_lifetimes, "1.23.0", Some(44524), None),
406 // Generic associated types (RFC 1598)
407 (active, generic_associated_types, "1.23.0", Some(44265), None),
409 // Resolve absolute paths as paths from other crates
410 (active, extern_absolute_paths, "1.24.0", Some(44660), Some(Edition::Edition2018)),
412 // `foo.rs` as an alternative to `foo/mod.rs`
413 (active, non_modrs_mods, "1.24.0", Some(44660), Some(Edition::Edition2018)),
416 (active, extern_in_paths, "1.23.0", Some(44660), None),
418 // Use `?` as the Kleene "at most one" operator
419 (active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
421 // Infer outlives requirements; RFC 2093
422 (active, infer_outlives_requirements, "1.26.0", Some(44493), None),
424 // Infer static outlives requirements; RFC 2093
425 (active, infer_static_outlives_requirements, "1.26.0", Some(44493), None),
427 // Multiple patterns with `|` in `if let` and `while let`
428 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
430 // Parentheses in patterns
431 (active, pattern_parentheses, "1.26.0", Some(51087), None),
433 // Allows `#[repr(packed)]` attribute on structs
434 (active, repr_packed, "1.26.0", Some(33158), None),
436 // `use path as _;` and `extern crate c as _;`
437 (active, underscore_imports, "1.26.0", Some(48216), None),
439 // Allows macro invocations in `extern {}` blocks
440 (active, macros_in_extern, "1.27.0", Some(49476), None),
442 // `existential type`
443 (active, existential_type, "1.28.0", Some(34511), None),
445 // unstable #[target_feature] directives
446 (active, arm_target_feature, "1.27.0", Some(44839), None),
447 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
448 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
449 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
450 (active, mips_target_feature, "1.27.0", Some(44839), None),
451 (active, avx512_target_feature, "1.27.0", Some(44839), None),
452 (active, mmx_target_feature, "1.27.0", Some(44839), None),
453 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
454 (active, tbm_target_feature, "1.27.0", Some(44839), None),
455 (active, wasm_target_feature, "1.30.0", Some(44839), None),
457 // Allows macro invocations on modules expressions and statements and
458 // procedural macros to expand to non-items.
459 (active, proc_macro_mod, "1.27.0", Some(38356), None),
460 (active, proc_macro_expr, "1.27.0", Some(38356), None),
461 (active, proc_macro_non_items, "1.27.0", Some(38356), None),
462 (active, proc_macro_gen, "1.27.0", Some(38356), None),
464 // #[doc(alias = "...")]
465 (active, doc_alias, "1.27.0", Some(50146), None),
467 // Access to crate names passed via `--extern` through prelude
468 (active, extern_prelude, "1.27.0", Some(44660), Some(Edition::Edition2018)),
471 (active, tool_lints, "1.28.0", Some(44690), None),
473 // Allows irrefutable patterns in if-let and while-let statements (RFC 2086)
474 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
476 // Allows use of the :literal macro fragment specifier (RFC 1576)
477 (active, macro_literal_matcher, "1.27.0", Some(35625), None),
479 // inconsistent bounds in where clauses
480 (active, trivial_bounds, "1.28.0", Some(48214), None),
483 (active, label_break_value, "1.28.0", Some(48594), None),
485 // Integer match exhaustiveness checking
486 (active, exhaustive_integer_patterns, "1.30.0", Some(50907), None),
488 // RFC 2070: #[panic_implementation] / #[panic_handler]
489 (active, panic_implementation, "1.28.0", Some(44489), None),
490 (active, panic_handler, "1.30.0", Some(44489), None),
492 // #[doc(keyword = "...")]
493 (active, doc_keyword, "1.28.0", Some(51315), None),
495 // Allows async and await syntax
496 (active, async_await, "1.28.0", Some(50547), None),
498 // #[alloc_error_handler]
499 (active, alloc_error_handler, "1.29.0", Some(51540), None),
501 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
503 // impl<I:Iterator> Iterator for &mut Iterator
504 // impl Debug for Foo<'_>
505 (active, impl_header_lifetime_elision, "1.30.0", Some(15872), Some(Edition::Edition2018)),
507 // Support for arbitrary delimited token streams in non-macro attributes
508 (active, unrestricted_attribute_tokens, "1.30.0", Some(44690), None),
510 // Allows `use x::y;` to resolve through `self::x`, not just `::x`
511 (active, uniform_paths, "1.30.0", Some(53130), None),
513 // Allows `Self` in type definitions
514 (active, self_in_typedefs, "1.30.0", Some(49303), None),
516 // unsized rvalues at arguments and parameters
517 (active, unsized_locals, "1.30.0", Some(48055), None),
521 (active, custom_test_frameworks, "1.30.0", Some(50297), None),
525 (removed, import_shadowing, "1.0.0", None, None, None),
526 (removed, managed_boxes, "1.0.0", None, None, None),
527 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
528 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
529 (removed, reflect, "1.0.0", Some(27749), None, None),
530 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
531 (removed, opt_out_copy, "1.0.0", None, None, None),
532 (removed, quad_precision_float, "1.0.0", None, None, None),
533 (removed, struct_inherit, "1.0.0", None, None, None),
534 (removed, test_removed_feature, "1.0.0", None, None, None),
535 (removed, visible_private_types, "1.0.0", None, None, None),
536 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
537 // Allows using items which are missing stability attributes
539 (removed, unmarked_api, "1.0.0", None, None, None),
540 (removed, pushpop_unsafe, "1.2.0", None, None, None),
541 (removed, allocator, "1.0.0", None, None, None),
542 (removed, simd, "1.0.0", Some(27731), None,
543 Some("removed in favor of `#[repr(simd)]`")),
544 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
545 Some("merged into `#![feature(slice_patterns)]`")),
546 (removed, macro_reexport, "1.0.0", Some(29638), None,
547 Some("subsumed by `pub use`")),
551 (stable_removed, no_stack_check, "1.0.0", None, None),
555 (accepted, associated_types, "1.0.0", None, None),
556 // allow overloading augmented assignment operations like `a += b`
557 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
558 // allow empty structs and enum variants with braces
559 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
560 // Allows indexing into constant arrays.
561 (accepted, const_indexing, "1.26.0", Some(29947), None),
562 (accepted, default_type_params, "1.0.0", None, None),
563 (accepted, globs, "1.0.0", None, None),
564 (accepted, if_let, "1.0.0", None, None),
565 // A temporary feature gate used to enable parser extensions needed
566 // to bootstrap fix for #5723.
567 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
568 (accepted, macro_rules, "1.0.0", None, None),
569 // Allows using #![no_std]
570 (accepted, no_std, "1.6.0", None, None),
571 (accepted, slicing_syntax, "1.0.0", None, None),
572 (accepted, struct_variant, "1.0.0", None, None),
573 // These are used to test this portion of the compiler, they don't actually
575 (accepted, test_accepted_feature, "1.0.0", None, None),
576 (accepted, tuple_indexing, "1.0.0", None, None),
577 // Allows macros to appear in the type position.
578 (accepted, type_macros, "1.13.0", Some(27245), None),
579 (accepted, while_let, "1.0.0", None, None),
580 // Allows `#[deprecated]` attribute
581 (accepted, deprecated, "1.9.0", Some(29935), None),
583 (accepted, question_mark, "1.13.0", Some(31436), None),
584 // Allows `..` in tuple (struct) patterns
585 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
586 (accepted, item_like_imports, "1.15.0", Some(35120), None),
587 // Allows using `Self` and associated types in struct expressions and patterns.
588 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
589 // elide `'static` lifetimes in `static`s and `const`s
590 (accepted, static_in_const, "1.17.0", Some(35897), None),
591 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
592 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
593 // Allows the definition recursive static items.
594 (accepted, static_recursion, "1.17.0", Some(29719), None),
595 // pub(restricted) visibilities (RFC 1422)
596 (accepted, pub_restricted, "1.18.0", Some(32409), None),
597 // The #![windows_subsystem] attribute
598 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
599 // Allows `break {expr}` with a value inside `loop`s.
600 (accepted, loop_break_value, "1.19.0", Some(37339), None),
601 // Permits numeric fields in struct expressions and patterns.
602 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
603 // Coerces non capturing closures to function pointers
604 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
605 // Allows attributes on struct literal fields.
606 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
607 // Allows the definition of associated constants in `trait` or `impl`
609 (accepted, associated_consts, "1.20.0", Some(29646), None),
610 // Usage of the `compile_error!` macro
611 (accepted, compile_error, "1.20.0", Some(40872), None),
612 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
613 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
614 // Allow Drop types in constants (RFC 1440)
615 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
616 // Allows the sysV64 ABI to be specified on all platforms
617 // instead of just the platforms on which it is the C ABI
618 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
619 // Allows `repr(align(16))` struct attribute (RFC 1358)
620 (accepted, repr_align, "1.25.0", Some(33626), None),
621 // allow '|' at beginning of match arms (RFC 1925)
622 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
623 // Nested groups in `use` (RFC 2128)
624 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
626 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
627 // allow `..=` in patterns (RFC 1192)
628 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
629 // Termination trait in main (RFC 1937)
630 (accepted, termination_trait, "1.26.0", Some(43301), None),
631 // Copy/Clone closures (RFC 2132)
632 (accepted, clone_closures, "1.26.0", Some(44490), None),
633 (accepted, copy_closures, "1.26.0", Some(44490), None),
634 // Allows `impl Trait` in function arguments.
635 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
636 // Allows `impl Trait` in function return types.
637 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
639 (accepted, i128_type, "1.26.0", Some(35118), None),
640 // Default match binding modes (RFC 2005)
641 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
642 // allow `'_` placeholder lifetimes
643 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
644 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
645 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
646 // Allows cfg(target_feature = "...").
647 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
648 // Allows #[target_feature(...)]
649 (accepted, target_feature, "1.27.0", None, None),
650 // Trait object syntax with `dyn` prefix
651 (accepted, dyn_trait, "1.27.0", Some(44662), None),
652 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
653 (accepted, fn_must_use, "1.27.0", Some(43302), None),
654 // Allows use of the :lifetime macro fragment specifier
655 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
656 // Termination trait in tests (RFC 1937)
657 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
658 // The #[global_allocator] attribute
659 (accepted, global_allocator, "1.28.0", Some(27389), None),
660 // Allows `#[repr(transparent)]` attribute on newtype structs
661 (accepted, repr_transparent, "1.28.0", Some(43036), None),
662 // Defining procedural macros in `proc-macro` crates
663 (accepted, proc_macro, "1.29.0", Some(38356), None),
664 // Allows use of the :vis macro fragment specifier
665 (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
666 // Allows importing and reexporting macros with `use`,
667 // enables macro modularization in general.
668 (accepted, use_extern_macros, "1.30.0", Some(35896), None),
669 // Allows keywords to be escaped for use as identifiers
670 (accepted, raw_identifiers, "1.30.0", Some(48589), None),
671 // Attributes scoped to tools
672 (accepted, tool_attributes, "1.30.0", Some(44690), None),
673 // Allows multi-segment paths in attributes and derives
674 (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
675 // Allows all literals in attribute lists and values of key-value pairs.
676 (accepted, attr_literals, "1.30.0", Some(34981), None),
679 // If you change this, please modify src/doc/unstable-book as well. You must
680 // move that documentation into the relevant place in the other docs, and
681 // remove the chapter on the flag.
683 #[derive(Copy, Clone, PartialEq, Debug)]
684 pub enum AttributeType {
685 /// Normal, builtin attribute that is consumed
686 /// by the compiler before the unused_attribute check
689 /// Builtin attribute that may not be consumed by the compiler
690 /// before the unused_attribute check. These attributes
691 /// will be ignored by the unused_attribute lint
694 /// Builtin attribute that is only allowed at the crate level
698 pub enum AttributeGate {
699 /// Is gated by a given feature gate, reason
700 /// and function to check if enabled
701 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
703 /// Ungated attribute, can be used on all release channels
708 fn is_deprecated(&self) -> bool {
710 Gated(Stability::Deprecated(_), ..) => true,
716 #[derive(Copy, Clone, Debug)]
719 // Argument is tracking issue link.
720 Deprecated(&'static str),
724 impl ::std::fmt::Debug for AttributeGate {
725 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
727 Gated(ref stab, name, expl, _) =>
728 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
729 Ungated => write!(fmt, "Ungated")
734 macro_rules! cfg_fn {
735 ($field: ident) => {{
736 fn f(features: &Features) -> bool {
739 f as fn(&Features) -> bool
743 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
744 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
747 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
748 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
751 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
752 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
755 // Attributes that have a special meaning to rustc or rustdoc
756 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
759 ("warn", Normal, Ungated),
760 ("allow", Normal, Ungated),
761 ("forbid", Normal, Ungated),
762 ("deny", Normal, Ungated),
764 ("macro_use", Normal, Ungated),
765 ("macro_export", Normal, Ungated),
766 ("plugin_registrar", Normal, Ungated),
768 ("cfg", Normal, Ungated),
769 ("cfg_attr", Normal, Ungated),
770 ("main", Normal, Ungated),
771 ("start", Normal, Ungated),
772 ("repr", Normal, Ungated),
773 ("path", Normal, Ungated),
774 ("abi", Normal, Ungated),
775 ("automatically_derived", Normal, Ungated),
776 ("no_mangle", Normal, Ungated),
777 ("no_link", Normal, Ungated),
778 ("derive", Normal, Ungated),
779 ("should_panic", Normal, Ungated),
780 ("ignore", Normal, Ungated),
781 ("no_implicit_prelude", Normal, Ungated),
782 ("reexport_test_harness_main", Normal, Ungated),
783 ("link_args", Normal, Gated(Stability::Unstable,
785 "the `link_args` attribute is experimental and not \
786 portable across platforms, it is recommended to \
787 use `#[link(name = \"foo\")] instead",
788 cfg_fn!(link_args))),
789 ("macro_escape", Normal, Ungated),
792 ("structural_match", Whitelisted, Gated(Stability::Unstable,
794 "the semantics of constant patterns is \
796 cfg_fn!(structural_match))),
799 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
801 "non exhaustive is an experimental feature",
802 cfg_fn!(non_exhaustive))),
804 ("plugin", CrateLevel, Gated(Stability::Unstable,
806 "compiler plugins are experimental \
810 ("no_std", CrateLevel, Ungated),
811 ("no_core", CrateLevel, Gated(Stability::Unstable,
813 "no_core is experimental",
815 ("lang", Normal, Gated(Stability::Unstable,
817 "language items are subject to change",
818 cfg_fn!(lang_items))),
819 ("linkage", Whitelisted, Gated(Stability::Unstable,
821 "the `linkage` attribute is experimental \
822 and not portable across platforms",
824 ("thread_local", Whitelisted, Gated(Stability::Unstable,
826 "`#[thread_local]` is an experimental feature, and does \
827 not currently handle destructors.",
828 cfg_fn!(thread_local))),
830 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
832 "the `#[rustc_on_unimplemented]` attribute \
833 is an experimental feature",
834 cfg_fn!(on_unimplemented))),
835 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
836 "rustc_const_unstable",
837 "the `#[rustc_const_unstable]` attribute \
838 is an internal feature",
839 cfg_fn!(rustc_const_unstable))),
840 ("global_allocator", Normal, Ungated),
841 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
842 "allocator_internals",
843 "the `#[default_lib_allocator]` \
844 attribute is an experimental feature",
845 cfg_fn!(allocator_internals))),
846 ("needs_allocator", Normal, Gated(Stability::Unstable,
847 "allocator_internals",
848 "the `#[needs_allocator]` \
849 attribute is an experimental \
851 cfg_fn!(allocator_internals))),
852 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
854 "the `#[panic_runtime]` attribute is \
855 an experimental feature",
856 cfg_fn!(panic_runtime))),
857 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
858 "needs_panic_runtime",
859 "the `#[needs_panic_runtime]` \
860 attribute is an experimental \
862 cfg_fn!(needs_panic_runtime))),
863 ("rustc_outlives", Normal, Gated(Stability::Unstable,
865 "the `#[rustc_outlives]` attribute \
866 is just used for rustc unit tests \
867 and will never be stable",
868 cfg_fn!(rustc_attrs))),
869 ("rustc_variance", Normal, Gated(Stability::Unstable,
871 "the `#[rustc_variance]` attribute \
872 is just used for rustc unit tests \
873 and will never be stable",
874 cfg_fn!(rustc_attrs))),
875 ("rustc_regions", Normal, Gated(Stability::Unstable,
877 "the `#[rustc_regions]` attribute \
878 is just used for rustc unit tests \
879 and will never be stable",
880 cfg_fn!(rustc_attrs))),
881 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
883 "the `#[rustc_error]` attribute \
884 is just used for rustc unit tests \
885 and will never be stable",
886 cfg_fn!(rustc_attrs))),
887 ("rustc_dump_user_substs", Whitelisted, Gated(Stability::Unstable,
890 is just used for rustc unit tests \
891 and will never be stable",
892 cfg_fn!(rustc_attrs))),
893 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
895 "the `#[rustc_if_this_changed]` attribute \
896 is just used for rustc unit tests \
897 and will never be stable",
898 cfg_fn!(rustc_attrs))),
899 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
901 "the `#[rustc_if_this_changed]` attribute \
902 is just used for rustc unit tests \
903 and will never be stable",
904 cfg_fn!(rustc_attrs))),
905 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
907 "the `#[rustc_dirty]` attribute \
908 is just used for rustc unit tests \
909 and will never be stable",
910 cfg_fn!(rustc_attrs))),
911 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
913 "the `#[rustc_clean]` attribute \
914 is just used for rustc unit tests \
915 and will never be stable",
916 cfg_fn!(rustc_attrs))),
917 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
920 is just used for rustc unit tests \
921 and will never be stable",
922 cfg_fn!(rustc_attrs))),
923 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
926 is just used for rustc unit tests \
927 and will never be stable",
928 cfg_fn!(rustc_attrs))),
929 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
932 is just used for rustc unit tests \
933 and will never be stable",
934 cfg_fn!(rustc_attrs))),
935 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
937 "internal rustc attributes will never be stable",
938 cfg_fn!(rustc_attrs))),
939 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
941 "internal rustc attributes will never be stable",
942 cfg_fn!(rustc_attrs))),
943 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
945 "the `#[rustc_mir]` attribute \
946 is just used for rustc unit tests \
947 and will never be stable",
948 cfg_fn!(rustc_attrs))),
949 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
951 "the `#[rustc_inherit_overflow_checks]` \
952 attribute is just used to control \
953 overflow checking behavior of several \
954 libcore functions that are inlined \
955 across crates and will never be stable",
956 cfg_fn!(rustc_attrs))),
958 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
960 "the `#[rustc_dump_program_clauses]` \
961 attribute is just used for rustc unit \
962 tests and will never be stable",
963 cfg_fn!(rustc_attrs))),
964 ("rustc_test_marker", Normal, Gated(Stability::Unstable,
966 "the `#[rustc_test_marker]` attribute \
967 is used internally to track tests",
968 cfg_fn!(rustc_attrs))),
971 ("nll", Whitelisted, Gated(Stability::Unstable,
973 "Non lexical lifetimes",
975 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
977 "the `#[compiler_builtins]` attribute is used to \
978 identify the `compiler_builtins` crate which \
979 contains compiler-rt intrinsics and will never be \
981 cfg_fn!(compiler_builtins))),
982 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
984 "the `#[sanitizer_runtime]` attribute is used to \
985 identify crates that contain the runtime of a \
986 sanitizer and will never be stable",
987 cfg_fn!(sanitizer_runtime))),
988 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
990 "the `#[profiler_runtime]` attribute is used to \
991 identify the `profiler_builtins` crate which \
992 contains the profiler runtime and will never be \
994 cfg_fn!(profiler_runtime))),
996 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
997 "allow_internal_unstable",
998 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
999 cfg_fn!(allow_internal_unstable))),
1001 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
1002 "allow_internal_unsafe",
1003 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
1004 cfg_fn!(allow_internal_unsafe))),
1006 ("fundamental", Whitelisted, Gated(Stability::Unstable,
1008 "the `#[fundamental]` attribute \
1009 is an experimental feature",
1010 cfg_fn!(fundamental))),
1012 ("proc_macro_derive", Normal, Ungated),
1014 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
1016 "internal implementation detail",
1017 cfg_fn!(rustc_attrs))),
1019 // FIXME: #14408 whitelist docs since rustdoc looks at them
1020 ("doc", Whitelisted, Ungated),
1022 // FIXME: #14406 these are processed in codegen, which happens after the
1024 ("cold", Whitelisted, Ungated),
1025 ("naked", Whitelisted, Gated(Stability::Unstable,
1027 "the `#[naked]` attribute \
1028 is an experimental feature",
1029 cfg_fn!(naked_functions))),
1030 ("target_feature", Whitelisted, Ungated),
1031 ("export_name", Whitelisted, Ungated),
1032 ("inline", Whitelisted, Ungated),
1033 ("link", Whitelisted, Ungated),
1034 ("link_name", Whitelisted, Ungated),
1035 ("link_section", Whitelisted, Ungated),
1036 ("no_builtins", Whitelisted, Ungated),
1037 ("no_mangle", Whitelisted, Ungated),
1038 ("no_debug", Whitelisted, Gated(
1039 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
1041 "the `#[no_debug]` attribute was an experimental feature that has been \
1042 deprecated due to lack of demand",
1043 cfg_fn!(no_debug))),
1044 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
1045 "omit_gdb_pretty_printer_section",
1046 "the `#[omit_gdb_pretty_printer_section]` \
1047 attribute is just used for the Rust test \
1049 cfg_fn!(omit_gdb_pretty_printer_section))),
1050 ("unsafe_destructor_blind_to_params",
1052 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761"),
1053 "dropck_parametricity",
1054 "unsafe_destructor_blind_to_params has been replaced by \
1055 may_dangle and will be removed in the future",
1056 cfg_fn!(dropck_parametricity))),
1059 Gated(Stability::Unstable,
1061 "may_dangle has unstable semantics and may be removed in the future",
1062 cfg_fn!(dropck_eyepatch))),
1063 ("unwind", Whitelisted, Gated(Stability::Unstable,
1064 "unwind_attributes",
1065 "#[unwind] is experimental",
1066 cfg_fn!(unwind_attributes))),
1067 ("used", Whitelisted, Gated(
1068 Stability::Unstable, "used",
1069 "the `#[used]` attribute is an experimental feature",
1073 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1075 "`#[prelude_import]` is for use by rustc only",
1076 cfg_fn!(prelude_import))),
1078 // FIXME: #14407 these are only looked at on-demand so we can't
1079 // guarantee they'll have already been checked
1080 ("rustc_deprecated", Whitelisted, Ungated),
1081 ("must_use", Whitelisted, Ungated),
1082 ("stable", Whitelisted, Ungated),
1083 ("unstable", Whitelisted, Ungated),
1084 ("deprecated", Normal, Ungated),
1086 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1088 "unboxed_closures are still evolving",
1089 cfg_fn!(unboxed_closures))),
1091 ("windows_subsystem", Whitelisted, Ungated),
1093 ("proc_macro_attribute", Normal, Ungated),
1094 ("proc_macro", Normal, Ungated),
1096 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
1097 "rustc_derive_registrar",
1098 "used internally by rustc",
1099 cfg_fn!(rustc_attrs))),
1101 ("allow_fail", Normal, Gated(Stability::Unstable,
1103 "allow_fail attribute is currently unstable",
1104 cfg_fn!(allow_fail))),
1106 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1108 "this is an internal attribute that will \
1110 cfg_fn!(rustc_attrs))),
1112 // whitelists "identity-like" conversion methods to suggest on type mismatch
1113 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1115 "this is an internal attribute that will \
1117 cfg_fn!(rustc_attrs))),
1119 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1121 "never will be stable",
1122 cfg_fn!(rustc_attrs))),
1125 ("infer_outlives_requirements", Normal, Gated(Stability::Unstable,
1126 "infer_outlives_requirements",
1127 "infer outlives requirements is an experimental feature",
1128 cfg_fn!(infer_outlives_requirements))),
1131 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1132 "infer_static_outlives_requirements",
1133 "infer 'static lifetime requirements",
1134 cfg_fn!(infer_static_outlives_requirements))),
1136 // RFC 2070 (deprecated attribute name)
1137 ("panic_implementation",
1139 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/44489\
1140 #issuecomment-415140224"),
1141 "panic_implementation",
1142 "This attribute was renamed to `panic_handler`",
1143 cfg_fn!(panic_implementation))),
1146 ("panic_handler", Normal, Gated(Stability::Unstable,
1148 "#[panic_handler] is an unstable feature",
1149 cfg_fn!(panic_handler))),
1151 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1152 "alloc_error_handler",
1153 "#[alloc_error_handler] is an unstable feature",
1154 cfg_fn!(alloc_error_handler))),
1156 // Crate level attributes
1157 ("crate_name", CrateLevel, Ungated),
1158 ("crate_type", CrateLevel, Ungated),
1159 ("crate_id", CrateLevel, Ungated),
1160 ("feature", CrateLevel, Ungated),
1161 ("no_start", CrateLevel, Ungated),
1162 ("no_main", CrateLevel, Ungated),
1163 ("no_builtins", CrateLevel, Ungated),
1164 ("recursion_limit", CrateLevel, Ungated),
1165 ("type_length_limit", CrateLevel, Ungated),
1166 ("test_runner", CrateLevel, Gated(Stability::Unstable,
1167 "custom_test_frameworks",
1168 EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
1169 cfg_fn!(custom_test_frameworks))),
1172 // cfg(...)'s that are feature gated
1173 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1174 // (name in cfg, feature, function to check if the feature is enabled)
1175 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1176 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1177 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1178 ("rustdoc", "doc_cfg", cfg_fn!(doc_cfg)),
1182 pub struct GatedCfg {
1188 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1189 let name = cfg.name().as_str();
1191 .position(|info| info.0 == name)
1200 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1201 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1202 if !has_feature(features) && !self.span.allows_unstable() {
1203 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1204 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1209 struct Context<'a> {
1210 features: &'a Features,
1211 parse_sess: &'a ParseSess,
1212 plugin_attributes: &'a [(String, AttributeType)],
1215 macro_rules! gate_feature_fn {
1216 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1217 let (cx, has_feature, span,
1218 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1219 let has_feature: bool = has_feature(&$cx.features);
1220 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1221 if !has_feature && !span.allows_unstable() {
1222 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1228 macro_rules! gate_feature {
1229 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1230 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1231 stringify!($feature), $explain, GateStrength::Hard)
1233 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1234 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1235 stringify!($feature), $explain, $level)
1239 impl<'a> Context<'a> {
1240 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1241 debug!("check_attribute(attr = {:?})", attr);
1242 let name = attr.name().as_str();
1243 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1245 if let Gated(_, name, desc, ref has_feature) = *gateage {
1246 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1247 } else if name == "doc" {
1248 if let Some(content) = attr.meta_item_list() {
1249 if content.iter().any(|c| c.check_name("include")) {
1250 gate_feature!(self, external_doc, attr.span,
1251 "#[doc(include = \"...\")] is experimental"
1256 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1260 for &(ref n, ref ty) in self.plugin_attributes {
1261 if attr.path == &**n {
1262 // Plugins can't gate attributes, so we don't check for it
1263 // unlike the code above; we only use this loop to
1264 // short-circuit to avoid the checks below
1265 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1269 if name.starts_with("rustc_") {
1270 gate_feature!(self, rustc_attrs, attr.span,
1271 "unless otherwise specified, attributes \
1272 with the prefix `rustc_` \
1273 are reserved for internal compiler diagnostics");
1274 } else if name.starts_with("derive_") {
1275 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1276 } else if !attr::is_known(attr) {
1277 // Only run the custom attribute lint during regular
1278 // feature gate checking. Macro gating runs
1279 // before the plugin attributes are registered
1280 // so we skip this then
1282 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1283 may have meaning added to it in the future", attr.path);
1284 gate_feature!(self, custom_attribute, attr.span, &msg);
1290 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1291 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1292 cx.check_attribute(attr, true);
1295 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1296 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1298 // FIXME (#28244): enforce that active features have issue numbers
1299 // assert!(issue.is_some())
1302 // search in Accepted, Removed, or Stable Removed features
1303 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1304 .find(|t| t.0 == feature);
1306 Some(&(_, _, issue, _)) => issue,
1307 None => panic!("Feature `{}` is not declared anywhere", feature),
1312 pub enum GateIssue {
1314 Library(Option<u32>)
1317 #[derive(Debug, Copy, Clone, PartialEq)]
1318 pub enum GateStrength {
1319 /// A hard error. (Most feature gates should use this.)
1321 /// Only a warning. (Use this only as backwards-compatibility demands.)
1325 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1327 feature_err(sess, feature, span, issue, explain).emit();
1330 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1331 explain: &str) -> DiagnosticBuilder<'a> {
1332 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1335 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1336 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1337 let diag = &sess.span_diagnostic;
1339 let issue = match issue {
1340 GateIssue::Language => find_lang_feature_issue(feature),
1341 GateIssue::Library(lib) => lib,
1344 let explanation = match issue {
1345 None | Some(0) => explain.to_owned(),
1346 Some(n) => format!("{} (see issue #{})", explain, n)
1349 let mut err = match level {
1350 GateStrength::Hard => {
1351 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1353 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1356 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1357 if sess.unstable_features.is_nightly_build() {
1358 err.help(&format!("add #![feature({})] to the \
1359 crate attributes to enable",
1363 // If we're on stable and only emitting a "soft" warning, add a note to
1364 // clarify that the feature isn't "on" (rather than being on but
1366 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1367 err.help("a nightly build of the compiler is required to enable this feature");
1374 const EXPLAIN_BOX_SYNTAX: &'static str =
1375 "box expression syntax is experimental; you can call `Box::new` instead.";
1377 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1378 "attributes on expressions are experimental.";
1380 pub const EXPLAIN_ASM: &'static str =
1381 "inline assembly is not stable enough for use and is subject to change";
1383 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1384 "`global_asm!` is not stable enough for use and is subject to change";
1386 pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &'static str =
1387 "custom test frameworks are an unstable feature";
1389 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1390 "`log_syntax!` is not stable enough for use and is subject to change";
1392 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1393 "`concat_idents` is not stable enough for use and is subject to change";
1395 pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
1396 "`format_args_nl` is only for internal language use and is subject to change";
1398 pub const EXPLAIN_TRACE_MACROS: &'static str =
1399 "`trace_macros` is not stable enough for use and is subject to change";
1400 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1401 "allow_internal_unstable side-steps feature gating and stability checks";
1402 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1403 "allow_internal_unsafe side-steps the unsafe_code lint";
1405 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1406 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1408 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1409 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1410 Prefer using procedural macro custom derive.";
1412 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1413 "attributes of the form `#[derive_*]` are reserved for the compiler";
1415 pub const EXPLAIN_LITERAL_MATCHER: &'static str =
1416 ":literal fragment specifier is experimental and subject to change";
1418 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1419 "unsized tuple coercion is not stable enough for use and is subject to change";
1421 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
1422 "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1424 struct PostExpansionVisitor<'a> {
1425 context: &'a Context<'a>,
1428 macro_rules! gate_feature_post {
1429 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1430 let (cx, span) = ($cx, $span);
1431 if !span.allows_unstable() {
1432 gate_feature!(cx.context, $feature, span, $explain)
1435 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1436 let (cx, span) = ($cx, $span);
1437 if !span.allows_unstable() {
1438 gate_feature!(cx.context, $feature, span, $explain, $level)
1443 impl<'a> PostExpansionVisitor<'a> {
1444 fn check_abi(&self, abi: Abi, span: Span) {
1446 Abi::RustIntrinsic => {
1447 gate_feature_post!(&self, intrinsics, span,
1448 "intrinsics are subject to change");
1450 Abi::PlatformIntrinsic => {
1451 gate_feature_post!(&self, platform_intrinsics, span,
1452 "platform intrinsics are experimental and possibly buggy");
1454 Abi::Vectorcall => {
1455 gate_feature_post!(&self, abi_vectorcall, span,
1456 "vectorcall is experimental and subject to change");
1459 gate_feature_post!(&self, abi_thiscall, span,
1460 "thiscall is experimental and subject to change");
1463 gate_feature_post!(&self, unboxed_closures, span,
1464 "rust-call ABI is subject to change");
1467 gate_feature_post!(&self, abi_ptx, span,
1468 "PTX ABIs are experimental and subject to change");
1470 Abi::Unadjusted => {
1471 gate_feature_post!(&self, abi_unadjusted, span,
1472 "unadjusted ABI is an implementation detail and perma-unstable");
1474 Abi::Msp430Interrupt => {
1475 gate_feature_post!(&self, abi_msp430_interrupt, span,
1476 "msp430-interrupt ABI is experimental and subject to change");
1478 Abi::X86Interrupt => {
1479 gate_feature_post!(&self, abi_x86_interrupt, span,
1480 "x86-interrupt ABI is experimental and subject to change");
1482 Abi::AmdGpuKernel => {
1483 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1484 "amdgpu-kernel ABI is experimental and subject to change");
1500 impl<'a> PostExpansionVisitor<'a> {
1501 fn whole_crate_feature_gates(&mut self, _krate: &ast::Crate) {
1502 for &(ident, span) in &*self.context.parse_sess.non_modrs_mods.borrow() {
1503 if !span.allows_unstable() {
1504 let cx = &self.context;
1505 let level = GateStrength::Hard;
1506 let has_feature = cx.features.non_modrs_mods;
1507 let name = "non_modrs_mods";
1508 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}",
1509 name, span, has_feature);
1511 if !has_feature && !span.allows_unstable() {
1512 leveled_feature_err(
1513 cx.parse_sess, name, span, GateIssue::Language,
1514 "mod statements in non-mod.rs files are unstable", level
1516 .help(&format!("on stable builds, rename this file to {}{}mod.rs",
1517 ident, path::MAIN_SEPARATOR))
1525 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1526 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1527 if !attr.span.allows_unstable() {
1528 // check for gated attributes
1529 self.context.check_attribute(attr, false);
1532 if attr.check_name("doc") {
1533 if let Some(content) = attr.meta_item_list() {
1534 if content.len() == 1 && content[0].check_name("cfg") {
1535 gate_feature_post!(&self, doc_cfg, attr.span,
1536 "#[doc(cfg(...))] is experimental"
1538 } else if content.iter().any(|c| c.check_name("masked")) {
1539 gate_feature_post!(&self, doc_masked, attr.span,
1540 "#[doc(masked)] is experimental"
1542 } else if content.iter().any(|c| c.check_name("spotlight")) {
1543 gate_feature_post!(&self, doc_spotlight, attr.span,
1544 "#[doc(spotlight)] is experimental"
1546 } else if content.iter().any(|c| c.check_name("alias")) {
1547 gate_feature_post!(&self, doc_alias, attr.span,
1548 "#[doc(alias = \"...\")] is experimental"
1550 } else if content.iter().any(|c| c.check_name("keyword")) {
1551 gate_feature_post!(&self, doc_keyword, attr.span,
1552 "#[doc(keyword = \"...\")] is experimental"
1558 if !self.context.features.unrestricted_attribute_tokens {
1559 // Unfortunately, `parse_meta` cannot be called speculatively
1560 // because it can report errors by itself, so we have to call it
1561 // only if the feature is disabled.
1562 if let Err(mut err) = attr.parse_meta(self.context.parse_sess) {
1563 err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
1568 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1569 if !name.as_str().is_ascii() {
1570 gate_feature_post!(&self,
1572 self.context.parse_sess.source_map().def_span(sp),
1573 "non-ascii idents are not fully supported.");
1577 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1578 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1579 if ident.name == "_" {
1580 gate_feature_post!(&self, underscore_imports, use_tree.span,
1581 "renaming imports with `_` is unstable");
1585 visit::walk_use_tree(self, use_tree, id);
1588 fn visit_item(&mut self, i: &'a ast::Item) {
1590 ast::ItemKind::ExternCrate(_) => {
1591 if i.ident.name == "_" {
1592 gate_feature_post!(&self, underscore_imports, i.span,
1593 "renaming extern crates with `_` is unstable");
1597 ast::ItemKind::ForeignMod(ref foreign_module) => {
1598 self.check_abi(foreign_module.abi, i.span);
1601 ast::ItemKind::Fn(..) => {
1602 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1603 gate_feature_post!(&self, plugin_registrar, i.span,
1604 "compiler plugins are experimental and possibly buggy");
1606 if attr::contains_name(&i.attrs[..], "start") {
1607 gate_feature_post!(&self, start, i.span,
1608 "a #[start] function is an experimental \
1609 feature whose signature may change \
1612 if attr::contains_name(&i.attrs[..], "main") {
1613 gate_feature_post!(&self, main, i.span,
1614 "declaration of a nonstandard #[main] \
1615 function may change over time, for now \
1616 a top-level `fn main()` is required");
1620 ast::ItemKind::Struct(..) => {
1621 if let Some(attr) = attr::find_by_name(&i.attrs[..], "repr") {
1622 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1623 if item.check_name("simd") {
1624 gate_feature_post!(&self, repr_simd, attr.span,
1625 "SIMD types are experimental and possibly buggy");
1627 if let Some((name, _)) = item.name_value_literal() {
1628 if name == "packed" {
1629 gate_feature_post!(&self, repr_packed, attr.span,
1630 "the `#[repr(packed(n))]` attribute \
1638 ast::ItemKind::TraitAlias(..) => {
1639 gate_feature_post!(&self, trait_alias,
1641 "trait aliases are not yet fully implemented");
1644 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1645 if polarity == ast::ImplPolarity::Negative {
1646 gate_feature_post!(&self, optin_builtin_traits,
1648 "negative trait bounds are not yet fully implemented; \
1649 use marker types for now");
1652 if let ast::Defaultness::Default = defaultness {
1653 gate_feature_post!(&self, specialization,
1655 "specialization is unstable");
1659 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1660 gate_feature_post!(&self, optin_builtin_traits,
1662 "auto traits are experimental and possibly buggy");
1665 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1666 let msg = "`macro` is experimental";
1667 gate_feature_post!(&self, decl_macro, i.span, msg);
1670 ast::ItemKind::Existential(..) => {
1675 "existential types are unstable"
1682 visit::walk_item(self, i);
1685 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1687 ast::ForeignItemKind::Fn(..) |
1688 ast::ForeignItemKind::Static(..) => {
1689 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1690 let links_to_llvm = match link_name {
1691 Some(val) => val.as_str().starts_with("llvm."),
1695 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1696 "linking to LLVM intrinsics is experimental");
1699 ast::ForeignItemKind::Ty => {
1700 gate_feature_post!(&self, extern_types, i.span,
1701 "extern types are experimental");
1703 ast::ForeignItemKind::Macro(..) => {}
1706 visit::walk_foreign_item(self, i)
1709 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1711 ast::TyKind::BareFn(ref bare_fn_ty) => {
1712 self.check_abi(bare_fn_ty.abi, ty.span);
1714 ast::TyKind::Never => {
1715 gate_feature_post!(&self, never_type, ty.span,
1716 "The `!` type is experimental");
1720 visit::walk_ty(self, ty)
1723 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1724 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1725 if let ast::TyKind::Never = output_ty.node {
1728 self.visit_ty(output_ty)
1733 fn visit_expr(&mut self, e: &'a ast::Expr) {
1735 ast::ExprKind::Box(_) => {
1736 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1738 ast::ExprKind::Type(..) => {
1739 gate_feature_post!(&self, type_ascription, e.span,
1740 "type ascription is experimental");
1742 ast::ExprKind::ObsoleteInPlace(..) => {
1743 // these get a hard error in ast-validation
1745 ast::ExprKind::Yield(..) => {
1746 gate_feature_post!(&self, generators,
1748 "yield syntax is experimental");
1750 ast::ExprKind::TryBlock(_) => {
1751 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
1753 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1755 gate_feature_post!(&self, if_while_or_patterns, e.span,
1756 "multiple patterns in `if let` and `while let` are unstable");
1759 ast::ExprKind::Block(_, opt_label) => {
1760 if let Some(label) = opt_label {
1761 gate_feature_post!(&self, label_break_value, label.ident.span,
1762 "labels on blocks are unstable");
1765 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1766 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1768 ast::ExprKind::Async(..) => {
1769 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1773 visit::walk_expr(self, e);
1776 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1777 visit::walk_arm(self, arm)
1780 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1781 match pattern.node {
1782 PatKind::Slice(_, Some(ref subslice), _) => {
1783 gate_feature_post!(&self, slice_patterns,
1785 "syntax for subslices in slice patterns is not yet stabilized");
1787 PatKind::Box(..) => {
1788 gate_feature_post!(&self, box_patterns,
1790 "box pattern syntax is experimental");
1792 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1793 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1794 "exclusive range pattern syntax is experimental");
1796 PatKind::Paren(..) => {
1797 gate_feature_post!(&self, pattern_parentheses, pattern.span,
1798 "parentheses in patterns are unstable");
1802 visit::walk_pat(self, pattern)
1805 fn visit_fn(&mut self,
1806 fn_kind: FnKind<'a>,
1807 fn_decl: &'a ast::FnDecl,
1811 FnKind::ItemFn(_, header, _, _) => {
1812 // check for const fn and async fn declarations
1813 if header.asyncness.is_async() {
1814 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1816 if header.constness.node == ast::Constness::Const {
1817 gate_feature_post!(&self, min_const_fn, span, "const fn is unstable");
1819 // stability of const fn methods are covered in
1820 // visit_trait_item and visit_impl_item below; this is
1821 // because default methods don't pass through this
1824 self.check_abi(header.abi, span);
1826 FnKind::Method(_, sig, _, _) => {
1827 self.check_abi(sig.header.abi, span);
1831 visit::walk_fn(self, fn_kind, fn_decl, span);
1834 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1836 ast::TraitItemKind::Method(ref sig, ref block) => {
1837 if block.is_none() {
1838 self.check_abi(sig.header.abi, ti.span);
1840 if sig.header.constness.node == ast::Constness::Const {
1841 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1844 ast::TraitItemKind::Type(_, ref default) => {
1845 // We use three if statements instead of something like match guards so that all
1846 // of these errors can be emitted if all cases apply.
1847 if default.is_some() {
1848 gate_feature_post!(&self, associated_type_defaults, ti.span,
1849 "associated type defaults are unstable");
1851 if !ti.generics.params.is_empty() {
1852 gate_feature_post!(&self, generic_associated_types, ti.span,
1853 "generic associated types are unstable");
1855 if !ti.generics.where_clause.predicates.is_empty() {
1856 gate_feature_post!(&self, generic_associated_types, ti.span,
1857 "where clauses on associated types are unstable");
1862 visit::walk_trait_item(self, ti);
1865 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1866 if ii.defaultness == ast::Defaultness::Default {
1867 gate_feature_post!(&self, specialization,
1869 "specialization is unstable");
1873 ast::ImplItemKind::Method(ref sig, _) => {
1874 if sig.header.constness.node == ast::Constness::Const {
1875 gate_feature_post!(&self, min_const_fn, ii.span, "const fn is unstable");
1878 ast::ImplItemKind::Existential(..) => {
1883 "existential types are unstable"
1886 ast::ImplItemKind::Type(_) => {
1887 if !ii.generics.params.is_empty() {
1888 gate_feature_post!(&self, generic_associated_types, ii.span,
1889 "generic associated types are unstable");
1891 if !ii.generics.where_clause.predicates.is_empty() {
1892 gate_feature_post!(&self, generic_associated_types, ii.span,
1893 "where clauses on associated types are unstable");
1898 visit::walk_impl_item(self, ii);
1901 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1902 for segment in &path.segments {
1903 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1904 // For such macros identifiers must have empty context, because this context is
1905 // used during name resolution and produced names must be unhygienic for compatibility.
1906 // On the other hand, we need the actual non-empty context for feature gate checking
1907 // because it's hygienic even for legacy macros. As previously stated, such context
1908 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1909 // there while keeping location info from the ident span.
1910 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1911 if segment.ident.name == keywords::Crate.name() {
1912 gate_feature_post!(&self, crate_in_paths, span,
1913 "`crate` in paths is experimental");
1914 } else if segment.ident.name == keywords::Extern.name() {
1915 gate_feature_post!(&self, extern_in_paths, span,
1916 "`extern` in paths is experimental");
1920 visit::walk_path(self, path);
1923 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1924 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1925 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1926 "`crate` visibility modifier is experimental");
1928 visit::walk_vis(self, vis);
1932 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1933 crate_edition: Edition) -> Features {
1934 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1935 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1936 if let Some(reason) = reason {
1937 err.span_note(span, reason);
1942 // Some features are known to be incomplete and using them is likely to have
1943 // unanticipated results, such as compiler crashes. We warn the user about these
1945 let incomplete_features = ["generic_associated_types"];
1947 let mut features = Features::new();
1948 let mut edition_enabled_features = FxHashMap();
1950 for &edition in ALL_EDITIONS {
1951 if edition <= crate_edition {
1952 // The `crate_edition` implies its respective umbrella feature-gate
1953 // (i.e. `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
1954 edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
1958 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1959 if let Some(f_edition) = f_edition {
1960 if f_edition <= crate_edition {
1961 set(&mut features, DUMMY_SP);
1962 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1967 // Process the edition umbrella feature-gates first, to ensure
1968 // `edition_enabled_features` is completed before it's queried.
1969 for attr in krate_attrs {
1970 if !attr.check_name("feature") {
1974 let list = match attr.meta_item_list() {
1980 let name = if let Some(word) = mi.word() {
1986 if incomplete_features.iter().any(|f| *f == name.as_str()) {
1987 span_handler.struct_span_warn(
1990 "the feature `{}` is incomplete and may cause the compiler to crash",
1996 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1997 if *edition <= crate_edition {
2001 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
2002 if let Some(f_edition) = f_edition {
2003 if f_edition <= *edition {
2004 // FIXME(Manishearth) there is currently no way to set
2005 // lib features by edition
2006 set(&mut features, DUMMY_SP);
2007 edition_enabled_features.insert(Symbol::intern(name), *edition);
2015 for attr in krate_attrs {
2016 if !attr.check_name("feature") {
2020 let list = match attr.meta_item_list() {
2023 span_err!(span_handler, attr.span, E0555,
2024 "malformed feature attribute, expected #![feature(...)]");
2030 let name = if let Some(word) = mi.word() {
2033 span_err!(span_handler, mi.span, E0556,
2034 "malformed feature, expected just one word");
2038 if let Some(edition) = edition_enabled_features.get(&name) {
2043 "the feature `{}` is included in the Rust {} edition",
2050 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
2051 // Handled in the separate loop above.
2055 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
2056 set(&mut features, mi.span);
2057 features.declared_lang_features.push((name, mi.span, None));
2061 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
2062 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
2063 if let Some((.., reason)) = removed.or(stable_removed) {
2064 feature_removed(span_handler, mi.span, *reason);
2068 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
2069 let since = Some(Symbol::intern(since));
2070 features.declared_lang_features.push((name, mi.span, since));
2074 features.declared_lib_features.push((name, mi.span));
2081 pub fn check_crate(krate: &ast::Crate,
2083 features: &Features,
2084 plugin_attributes: &[(String, AttributeType)],
2085 unstable: UnstableFeatures) {
2086 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2093 let visitor = &mut PostExpansionVisitor { context: &ctx };
2094 visitor.whole_crate_feature_gates(krate);
2095 visit::walk_crate(visitor, krate);
2098 #[derive(Clone, Copy, Hash)]
2099 pub enum UnstableFeatures {
2100 /// Hard errors for unstable features are active, as on
2101 /// beta/stable channels.
2103 /// Allow features to be activated, as on nightly.
2105 /// Errors are bypassed for bootstrapping. This is required any time
2106 /// during the build that feature-related lints are set to warn or above
2107 /// because the build turns on warnings-as-errors and uses lots of unstable
2108 /// features. As a result, this is always required for building Rust itself.
2112 impl UnstableFeatures {
2113 pub fn from_environment() -> UnstableFeatures {
2114 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2115 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2116 // Whether we should enable unstable features for bootstrapping
2117 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2118 match (disable_unstable_features, bootstrap) {
2119 (_, true) => UnstableFeatures::Cheat,
2120 (true, _) => UnstableFeatures::Disallow,
2121 (false, _) => UnstableFeatures::Allow
2125 pub fn is_nightly_build(&self) -> bool {
2127 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2133 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2134 unstable: UnstableFeatures) {
2135 let allow_features = match unstable {
2136 UnstableFeatures::Allow => true,
2137 UnstableFeatures::Disallow => false,
2138 UnstableFeatures::Cheat => true
2140 if !allow_features {
2141 for attr in &krate.attrs {
2142 if attr.check_name("feature") {
2143 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2144 span_err!(span_handler, attr.span, E0554,
2145 "#![feature] may not be used on the {} release channel",