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 // Allows module-level inline assembly by way of global_asm!()
353 (active, global_asm, "1.18.0", Some(35119), None),
355 // Allows overlapping impls of marker traits
356 (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
358 // Trait attribute to allow overlapping impls
359 (active, marker_trait_attr, "1.30.0", 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), None),
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),
400 // In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
401 (active, in_band_lifetimes, "1.23.0", Some(44524), None),
403 // Generic associated types (RFC 1598)
404 (active, generic_associated_types, "1.23.0", Some(44265), None),
407 (active, extern_in_paths, "1.23.0", Some(44660), None),
409 // Use `?` as the Kleene "at most one" operator
410 (active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
412 // Infer static outlives requirements; RFC 2093
413 (active, infer_static_outlives_requirements, "1.26.0", Some(44493), None),
415 // Multiple patterns with `|` in `if let` and `while let`
416 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
418 // Allows `#[repr(packed)]` attribute on structs
419 (active, repr_packed, "1.26.0", Some(33158), None),
421 // `use path as _;` and `extern crate c as _;`
422 (active, underscore_imports, "1.26.0", Some(48216), None),
424 // Allows macro invocations in `extern {}` blocks
425 (active, macros_in_extern, "1.27.0", Some(49476), None),
427 // `existential type`
428 (active, existential_type, "1.28.0", Some(34511), None),
430 // unstable #[target_feature] directives
431 (active, arm_target_feature, "1.27.0", Some(44839), None),
432 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
433 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
434 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
435 (active, mips_target_feature, "1.27.0", Some(44839), None),
436 (active, avx512_target_feature, "1.27.0", Some(44839), None),
437 (active, mmx_target_feature, "1.27.0", Some(44839), None),
438 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
439 (active, tbm_target_feature, "1.27.0", Some(44839), None),
440 (active, wasm_target_feature, "1.30.0", Some(44839), None),
442 // Allows macro invocations on modules expressions and statements and
443 // procedural macros to expand to non-items.
444 (active, proc_macro_mod, "1.27.0", Some(54727), None),
445 (active, proc_macro_expr, "1.27.0", Some(54727), None),
446 (active, proc_macro_non_items, "1.27.0", Some(54727), None),
447 (active, proc_macro_gen, "1.27.0", Some(54727), None),
449 // #[doc(alias = "...")]
450 (active, doc_alias, "1.27.0", Some(50146), None),
453 (active, tool_lints, "1.28.0", Some(44690), None),
455 // Allows irrefutable patterns in if-let and while-let statements (RFC 2086)
456 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
458 // Allows use of the :literal macro fragment specifier (RFC 1576)
459 (active, macro_literal_matcher, "1.27.0", Some(35625), None),
461 // inconsistent bounds in where clauses
462 (active, trivial_bounds, "1.28.0", Some(48214), None),
465 (active, label_break_value, "1.28.0", Some(48594), None),
467 // Integer match exhaustiveness checking
468 (active, exhaustive_integer_patterns, "1.30.0", Some(50907), None),
470 // RFC 2070: #[panic_implementation] / #[panic_handler]
471 (active, panic_implementation, "1.28.0", Some(44489), None),
473 // #[doc(keyword = "...")]
474 (active, doc_keyword, "1.28.0", Some(51315), None),
476 // Allows async and await syntax
477 (active, async_await, "1.28.0", Some(50547), None),
479 // #[alloc_error_handler]
480 (active, alloc_error_handler, "1.29.0", Some(51540), None),
482 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
484 // impl<I:Iterator> Iterator for &mut Iterator
485 // impl Debug for Foo<'_>
486 (active, impl_header_lifetime_elision, "1.30.0", Some(15872), Some(Edition::Edition2018)),
488 // Support for arbitrary delimited token streams in non-macro attributes
489 (active, unrestricted_attribute_tokens, "1.30.0", Some(44690), None),
491 // Allows `use x::y;` to resolve through `self::x`, not just `::x`
492 (active, uniform_paths, "1.30.0", Some(53130), None),
494 // Allows `Self` in type definitions
495 (active, self_in_typedefs, "1.30.0", Some(49303), None),
497 // Allows unsized rvalues at arguments and parameters
498 (active, unsized_locals, "1.30.0", Some(48055), None),
502 (active, custom_test_frameworks, "1.30.0", Some(50297), None),
504 // Non-builtin attributes in inner attribute position
505 (active, custom_inner_attributes, "1.30.0", Some(54726), None),
507 // Self struct constructor (RFC 2302)
508 (active, self_struct_ctor, "1.30.0", Some(51994), None),
510 // allow mixing of bind-by-move in patterns and references to
511 // those identifiers in guards, *if* we are using MIR-borrowck
512 // (aka NLL). Essentially this means you need to be on
513 // edition:2018 or later.
514 (active, bind_by_move_pattern_guards, "1.30.0", Some(15287), None),
516 // Allows `impl Trait` in bindings (`let`, `const`, `static`)
517 (active, impl_trait_in_bindings, "1.30.0", Some(34511), None),
521 (removed, import_shadowing, "1.0.0", None, None, None),
522 (removed, managed_boxes, "1.0.0", None, None, None),
523 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
524 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
525 (removed, reflect, "1.0.0", Some(27749), None, None),
526 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
527 (removed, opt_out_copy, "1.0.0", None, None, None),
528 (removed, quad_precision_float, "1.0.0", None, None, None),
529 (removed, struct_inherit, "1.0.0", None, None, None),
530 (removed, test_removed_feature, "1.0.0", None, None, None),
531 (removed, visible_private_types, "1.0.0", None, None, None),
532 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
533 // Allows using items which are missing stability attributes
535 (removed, unmarked_api, "1.0.0", None, None, None),
536 (removed, pushpop_unsafe, "1.2.0", None, None, None),
537 (removed, allocator, "1.0.0", None, None, None),
538 (removed, simd, "1.0.0", Some(27731), None,
539 Some("removed in favor of `#[repr(simd)]`")),
540 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
541 Some("merged into `#![feature(slice_patterns)]`")),
542 (removed, macro_reexport, "1.0.0", Some(29638), None,
543 Some("subsumed by `pub use`")),
547 (stable_removed, no_stack_check, "1.0.0", None, None),
551 (accepted, associated_types, "1.0.0", None, None),
552 // allow overloading augmented assignment operations like `a += b`
553 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
554 // allow empty structs and enum variants with braces
555 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
556 // Allows indexing into constant arrays.
557 (accepted, const_indexing, "1.26.0", Some(29947), None),
558 (accepted, default_type_params, "1.0.0", None, None),
559 (accepted, globs, "1.0.0", None, None),
560 (accepted, if_let, "1.0.0", None, None),
561 // A temporary feature gate used to enable parser extensions needed
562 // to bootstrap fix for #5723.
563 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
564 (accepted, macro_rules, "1.0.0", None, None),
565 // Allows using #![no_std]
566 (accepted, no_std, "1.6.0", None, None),
567 (accepted, slicing_syntax, "1.0.0", None, None),
568 (accepted, struct_variant, "1.0.0", None, None),
569 // These are used to test this portion of the compiler, they don't actually
571 (accepted, test_accepted_feature, "1.0.0", None, None),
572 (accepted, tuple_indexing, "1.0.0", None, None),
573 // Allows macros to appear in the type position.
574 (accepted, type_macros, "1.13.0", Some(27245), None),
575 (accepted, while_let, "1.0.0", None, None),
576 // Allows `#[deprecated]` attribute
577 (accepted, deprecated, "1.9.0", Some(29935), None),
579 (accepted, question_mark, "1.13.0", Some(31436), None),
580 // Allows `..` in tuple (struct) patterns
581 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
582 (accepted, item_like_imports, "1.15.0", Some(35120), None),
583 // Allows using `Self` and associated types in struct expressions and patterns.
584 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
585 // elide `'static` lifetimes in `static`s and `const`s
586 (accepted, static_in_const, "1.17.0", Some(35897), None),
587 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
588 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
589 // Allows the definition recursive static items.
590 (accepted, static_recursion, "1.17.0", Some(29719), None),
591 // pub(restricted) visibilities (RFC 1422)
592 (accepted, pub_restricted, "1.18.0", Some(32409), None),
593 // The #![windows_subsystem] attribute
594 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
595 // Allows `break {expr}` with a value inside `loop`s.
596 (accepted, loop_break_value, "1.19.0", Some(37339), None),
597 // Permits numeric fields in struct expressions and patterns.
598 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
599 // Coerces non capturing closures to function pointers
600 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
601 // Allows attributes on struct literal fields.
602 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
603 // Allows the definition of associated constants in `trait` or `impl`
605 (accepted, associated_consts, "1.20.0", Some(29646), None),
606 // Usage of the `compile_error!` macro
607 (accepted, compile_error, "1.20.0", Some(40872), None),
608 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
609 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
610 // Allow Drop types in constants (RFC 1440)
611 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
612 // Allows the sysV64 ABI to be specified on all platforms
613 // instead of just the platforms on which it is the C ABI
614 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
615 // Allows `repr(align(16))` struct attribute (RFC 1358)
616 (accepted, repr_align, "1.25.0", Some(33626), None),
617 // allow '|' at beginning of match arms (RFC 1925)
618 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
619 // Nested groups in `use` (RFC 2128)
620 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
622 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
623 // allow `..=` in patterns (RFC 1192)
624 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
625 // Termination trait in main (RFC 1937)
626 (accepted, termination_trait, "1.26.0", Some(43301), None),
627 // Copy/Clone closures (RFC 2132)
628 (accepted, clone_closures, "1.26.0", Some(44490), None),
629 (accepted, copy_closures, "1.26.0", Some(44490), None),
630 // Allows `impl Trait` in function arguments.
631 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
632 // Allows `impl Trait` in function return types.
633 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
635 (accepted, i128_type, "1.26.0", Some(35118), None),
636 // Default match binding modes (RFC 2005)
637 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
638 // allow `'_` placeholder lifetimes
639 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
640 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
641 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
642 // Allows cfg(target_feature = "...").
643 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
644 // Allows #[target_feature(...)]
645 (accepted, target_feature, "1.27.0", None, None),
646 // Trait object syntax with `dyn` prefix
647 (accepted, dyn_trait, "1.27.0", Some(44662), None),
648 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
649 (accepted, fn_must_use, "1.27.0", Some(43302), None),
650 // Allows use of the :lifetime macro fragment specifier
651 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
652 // Termination trait in tests (RFC 1937)
653 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
654 // The #[global_allocator] attribute
655 (accepted, global_allocator, "1.28.0", Some(27389), None),
656 // Allows `#[repr(transparent)]` attribute on newtype structs
657 (accepted, repr_transparent, "1.28.0", Some(43036), None),
658 // Defining procedural macros in `proc-macro` crates
659 (accepted, proc_macro, "1.29.0", Some(38356), None),
660 // `foo.rs` as an alternative to `foo/mod.rs`
661 (accepted, non_modrs_mods, "1.30.0", Some(44660), None),
662 // Allows use of the :vis macro fragment specifier
663 (accepted, macro_vis_matcher, "1.30.0", Some(41022), None),
664 // Allows importing and reexporting macros with `use`,
665 // enables macro modularization in general.
666 (accepted, use_extern_macros, "1.30.0", Some(35896), None),
667 // Allows keywords to be escaped for use as identifiers
668 (accepted, raw_identifiers, "1.30.0", Some(48589), None),
669 // Attributes scoped to tools
670 (accepted, tool_attributes, "1.30.0", Some(44690), None),
671 // Allows multi-segment paths in attributes and derives
672 (accepted, proc_macro_path_invoc, "1.30.0", Some(38356), None),
673 // Allows all literals in attribute lists and values of key-value pairs.
674 (accepted, attr_literals, "1.30.0", Some(34981), None),
675 // Infer outlives requirements; RFC 2093
676 (accepted, infer_outlives_requirements, "1.30.0", Some(44493), None),
677 (accepted, panic_handler, "1.30.0", Some(44489), None),
678 // Used to preserve symbols (see llvm.used)
679 (accepted, used, "1.30.0", Some(40289), None),
681 (accepted, crate_in_paths, "1.30.0", Some(45477), None),
682 // Resolve absolute paths as paths from other crates
683 (accepted, extern_absolute_paths, "1.30.0", Some(44660), None),
684 // Access to crate names passed via `--extern` through prelude
685 (accepted, extern_prelude, "1.30.0", Some(44660), None),
686 // Parentheses in patterns
687 (accepted, pattern_parentheses, "1.31.0", Some(51087), None),
690 // If you change this, please modify src/doc/unstable-book as well. You must
691 // move that documentation into the relevant place in the other docs, and
692 // remove the chapter on the flag.
694 #[derive(Copy, Clone, PartialEq, Debug)]
695 pub enum AttributeType {
696 /// Normal, builtin attribute that is consumed
697 /// by the compiler before the unused_attribute check
700 /// Builtin attribute that may not be consumed by the compiler
701 /// before the unused_attribute check. These attributes
702 /// will be ignored by the unused_attribute lint
705 /// Builtin attribute that is only allowed at the crate level
709 pub enum AttributeGate {
710 /// Is gated by a given feature gate, reason
711 /// and function to check if enabled
712 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
714 /// Ungated attribute, can be used on all release channels
719 fn is_deprecated(&self) -> bool {
721 Gated(Stability::Deprecated(_, _), ..) => true,
727 #[derive(Copy, Clone, Debug)]
730 // First argument is tracking issue link; second argument is an optional
731 // help message, which defaults to "remove this attribute"
732 Deprecated(&'static str, Option<&'static str>),
736 impl ::std::fmt::Debug for AttributeGate {
737 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
739 Gated(ref stab, name, expl, _) =>
740 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
741 Ungated => write!(fmt, "Ungated")
746 macro_rules! cfg_fn {
747 ($field: ident) => {{
748 fn f(features: &Features) -> bool {
751 f as fn(&Features) -> bool
755 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
756 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
759 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
760 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
763 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
764 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.path == builtin_name)
767 // Attributes that have a special meaning to rustc or rustdoc
768 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
771 ("warn", Normal, Ungated),
772 ("allow", Normal, Ungated),
773 ("forbid", Normal, Ungated),
774 ("deny", Normal, Ungated),
776 ("macro_use", Normal, Ungated),
777 ("macro_export", Normal, Ungated),
778 ("plugin_registrar", Normal, Ungated),
780 ("cfg", Normal, Ungated),
781 ("cfg_attr", Normal, Ungated),
782 ("main", Normal, Ungated),
783 ("start", Normal, Ungated),
784 ("repr", Normal, Ungated),
785 ("path", Normal, Ungated),
786 ("abi", Normal, Ungated),
787 ("automatically_derived", Normal, Ungated),
788 ("no_mangle", Normal, Ungated),
789 ("no_link", Normal, Ungated),
790 ("derive", Normal, Ungated),
791 ("should_panic", Normal, Ungated),
792 ("ignore", Normal, Ungated),
793 ("no_implicit_prelude", Normal, Ungated),
794 ("reexport_test_harness_main", Normal, Ungated),
795 ("link_args", Normal, Gated(Stability::Unstable,
797 "the `link_args` attribute is experimental and not \
798 portable across platforms, it is recommended to \
799 use `#[link(name = \"foo\")] instead",
800 cfg_fn!(link_args))),
801 ("macro_escape", Normal, Ungated),
804 ("structural_match", Whitelisted, Gated(Stability::Unstable,
806 "the semantics of constant patterns is \
808 cfg_fn!(structural_match))),
811 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
813 "non exhaustive is an experimental feature",
814 cfg_fn!(non_exhaustive))),
817 ("marker", Normal, Gated(Stability::Unstable,
819 "marker traits is an experimental feature",
820 cfg_fn!(marker_trait_attr))),
822 ("plugin", CrateLevel, Gated(Stability::Unstable,
824 "compiler plugins are experimental \
828 ("no_std", CrateLevel, Ungated),
829 ("no_core", CrateLevel, Gated(Stability::Unstable,
831 "no_core is experimental",
833 ("lang", Normal, Gated(Stability::Unstable,
835 "language items are subject to change",
836 cfg_fn!(lang_items))),
837 ("linkage", Whitelisted, Gated(Stability::Unstable,
839 "the `linkage` attribute is experimental \
840 and not portable across platforms",
842 ("thread_local", Whitelisted, Gated(Stability::Unstable,
844 "`#[thread_local]` is an experimental feature, and does \
845 not currently handle destructors.",
846 cfg_fn!(thread_local))),
848 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
850 "the `#[rustc_on_unimplemented]` attribute \
851 is an experimental feature",
852 cfg_fn!(on_unimplemented))),
853 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
854 "rustc_const_unstable",
855 "the `#[rustc_const_unstable]` attribute \
856 is an internal feature",
857 cfg_fn!(rustc_const_unstable))),
858 ("global_allocator", Normal, Ungated),
859 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
860 "allocator_internals",
861 "the `#[default_lib_allocator]` \
862 attribute is an experimental feature",
863 cfg_fn!(allocator_internals))),
864 ("needs_allocator", Normal, Gated(Stability::Unstable,
865 "allocator_internals",
866 "the `#[needs_allocator]` \
867 attribute is an experimental \
869 cfg_fn!(allocator_internals))),
870 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
872 "the `#[panic_runtime]` attribute is \
873 an experimental feature",
874 cfg_fn!(panic_runtime))),
875 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
876 "needs_panic_runtime",
877 "the `#[needs_panic_runtime]` \
878 attribute is an experimental \
880 cfg_fn!(needs_panic_runtime))),
881 ("rustc_outlives", Normal, Gated(Stability::Unstable,
883 "the `#[rustc_outlives]` attribute \
884 is just used for rustc unit tests \
885 and will never be stable",
886 cfg_fn!(rustc_attrs))),
887 ("rustc_variance", Normal, Gated(Stability::Unstable,
889 "the `#[rustc_variance]` attribute \
890 is just used for rustc unit tests \
891 and will never be stable",
892 cfg_fn!(rustc_attrs))),
893 ("rustc_regions", Normal, Gated(Stability::Unstable,
895 "the `#[rustc_regions]` attribute \
896 is just used for rustc unit tests \
897 and will never be stable",
898 cfg_fn!(rustc_attrs))),
899 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
901 "the `#[rustc_error]` attribute \
902 is just used for rustc unit tests \
903 and will never be stable",
904 cfg_fn!(rustc_attrs))),
905 ("rustc_dump_user_substs", Whitelisted, Gated(Stability::Unstable,
908 is just used for rustc unit tests \
909 and will never be stable",
910 cfg_fn!(rustc_attrs))),
911 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
913 "the `#[rustc_if_this_changed]` attribute \
914 is just used for rustc unit tests \
915 and will never be stable",
916 cfg_fn!(rustc_attrs))),
917 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
919 "the `#[rustc_if_this_changed]` attribute \
920 is just used for rustc unit tests \
921 and will never be stable",
922 cfg_fn!(rustc_attrs))),
923 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
925 "the `#[rustc_dirty]` attribute \
926 is just used for rustc unit tests \
927 and will never be stable",
928 cfg_fn!(rustc_attrs))),
929 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
931 "the `#[rustc_clean]` attribute \
932 is just used for rustc unit tests \
933 and will never be stable",
934 cfg_fn!(rustc_attrs))),
935 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
938 is just used for rustc unit tests \
939 and will never be stable",
940 cfg_fn!(rustc_attrs))),
941 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
944 is just used for rustc unit tests \
945 and will never be stable",
946 cfg_fn!(rustc_attrs))),
947 ("rustc_expected_cgu_reuse", Whitelisted, Gated(Stability::Unstable,
950 is just used for rustc unit tests \
951 and will never be stable",
952 cfg_fn!(rustc_attrs))),
953 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
956 is just used for rustc unit tests \
957 and will never be stable",
958 cfg_fn!(rustc_attrs))),
959 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
961 "internal rustc attributes will never be stable",
962 cfg_fn!(rustc_attrs))),
963 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
965 "internal rustc attributes will never be stable",
966 cfg_fn!(rustc_attrs))),
967 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
969 "the `#[rustc_mir]` attribute \
970 is just used for rustc unit tests \
971 and will never be stable",
972 cfg_fn!(rustc_attrs))),
973 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
975 "the `#[rustc_inherit_overflow_checks]` \
976 attribute is just used to control \
977 overflow checking behavior of several \
978 libcore functions that are inlined \
979 across crates and will never be stable",
980 cfg_fn!(rustc_attrs))),
982 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
984 "the `#[rustc_dump_program_clauses]` \
985 attribute is just used for rustc unit \
986 tests and will never be stable",
987 cfg_fn!(rustc_attrs))),
988 ("rustc_test_marker", Normal, Gated(Stability::Unstable,
990 "the `#[rustc_test_marker]` attribute \
991 is used internally to track tests",
992 cfg_fn!(rustc_attrs))),
993 ("rustc_test_marker2", Normal, Gated(Stability::Unstable,
995 "temporarily used by rustc to report some errors",
996 cfg_fn!(rustc_attrs))),
997 ("rustc_transparent_macro", Whitelisted, Gated(Stability::Unstable,
999 "used internally for testing macro hygiene",
1000 cfg_fn!(rustc_attrs))),
1003 ("nll", Whitelisted, Gated(Stability::Unstable,
1005 "Non lexical lifetimes",
1007 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
1008 "compiler_builtins",
1009 "the `#[compiler_builtins]` attribute is used to \
1010 identify the `compiler_builtins` crate which \
1011 contains compiler-rt intrinsics and will never be \
1013 cfg_fn!(compiler_builtins))),
1014 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
1015 "sanitizer_runtime",
1016 "the `#[sanitizer_runtime]` attribute is used to \
1017 identify crates that contain the runtime of a \
1018 sanitizer and will never be stable",
1019 cfg_fn!(sanitizer_runtime))),
1020 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
1022 "the `#[profiler_runtime]` attribute is used to \
1023 identify the `profiler_builtins` crate which \
1024 contains the profiler runtime and will never be \
1026 cfg_fn!(profiler_runtime))),
1028 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
1029 "allow_internal_unstable",
1030 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
1031 cfg_fn!(allow_internal_unstable))),
1033 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
1034 "allow_internal_unsafe",
1035 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
1036 cfg_fn!(allow_internal_unsafe))),
1038 ("fundamental", Whitelisted, Gated(Stability::Unstable,
1040 "the `#[fundamental]` attribute \
1041 is an experimental feature",
1042 cfg_fn!(fundamental))),
1044 ("proc_macro_derive", Normal, Ungated),
1046 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
1048 "internal implementation detail",
1049 cfg_fn!(rustc_attrs))),
1051 // FIXME: #14408 whitelist docs since rustdoc looks at them
1052 ("doc", Whitelisted, Ungated),
1054 // FIXME: #14406 these are processed in codegen, which happens after the
1056 ("cold", Whitelisted, Ungated),
1057 ("naked", Whitelisted, Gated(Stability::Unstable,
1059 "the `#[naked]` attribute \
1060 is an experimental feature",
1061 cfg_fn!(naked_functions))),
1062 ("target_feature", Whitelisted, Ungated),
1063 ("export_name", Whitelisted, Ungated),
1064 ("inline", Whitelisted, Ungated),
1065 ("link", Whitelisted, Ungated),
1066 ("link_name", Whitelisted, Ungated),
1067 ("link_section", Whitelisted, Ungated),
1068 ("no_builtins", Whitelisted, Ungated),
1069 ("no_mangle", Whitelisted, Ungated),
1070 ("no_debug", Whitelisted, Gated(
1071 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721", None),
1073 "the `#[no_debug]` attribute was an experimental feature that has been \
1074 deprecated due to lack of demand",
1075 cfg_fn!(no_debug))),
1076 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
1077 "omit_gdb_pretty_printer_section",
1078 "the `#[omit_gdb_pretty_printer_section]` \
1079 attribute is just used for the Rust test \
1081 cfg_fn!(omit_gdb_pretty_printer_section))),
1082 ("unsafe_destructor_blind_to_params",
1084 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761",
1085 Some("replace this attribute with `#[may_dangle]`")),
1086 "dropck_parametricity",
1087 "unsafe_destructor_blind_to_params has been replaced by \
1088 may_dangle and will be removed in the future",
1089 cfg_fn!(dropck_parametricity))),
1092 Gated(Stability::Unstable,
1094 "may_dangle has unstable semantics and may be removed in the future",
1095 cfg_fn!(dropck_eyepatch))),
1096 ("unwind", Whitelisted, Gated(Stability::Unstable,
1097 "unwind_attributes",
1098 "#[unwind] is experimental",
1099 cfg_fn!(unwind_attributes))),
1100 ("used", Whitelisted, Ungated),
1103 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1105 "`#[prelude_import]` is for use by rustc only",
1106 cfg_fn!(prelude_import))),
1108 // FIXME: #14407 these are only looked at on-demand so we can't
1109 // guarantee they'll have already been checked
1110 ("rustc_deprecated", Whitelisted, Ungated),
1111 ("must_use", Whitelisted, Ungated),
1112 ("stable", Whitelisted, Ungated),
1113 ("unstable", Whitelisted, Ungated),
1114 ("deprecated", Normal, Ungated),
1116 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1118 "unboxed_closures are still evolving",
1119 cfg_fn!(unboxed_closures))),
1121 ("windows_subsystem", Whitelisted, Ungated),
1123 ("proc_macro_attribute", Normal, Ungated),
1124 ("proc_macro", Normal, Ungated),
1126 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
1127 "rustc_derive_registrar",
1128 "used internally by rustc",
1129 cfg_fn!(rustc_attrs))),
1131 ("allow_fail", Normal, Gated(Stability::Unstable,
1133 "allow_fail attribute is currently unstable",
1134 cfg_fn!(allow_fail))),
1136 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1138 "this is an internal attribute that will \
1140 cfg_fn!(rustc_attrs))),
1142 // whitelists "identity-like" conversion methods to suggest on type mismatch
1143 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1145 "this is an internal attribute that will \
1147 cfg_fn!(rustc_attrs))),
1149 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1151 "never will be stable",
1152 cfg_fn!(rustc_attrs))),
1155 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1156 "infer_static_outlives_requirements",
1157 "infer 'static lifetime requirements",
1158 cfg_fn!(infer_static_outlives_requirements))),
1160 // RFC 2070 (deprecated attribute name)
1161 ("panic_implementation",
1163 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/44489\
1164 #issuecomment-415140224",
1165 Some("replace this attribute with `#[panic_handler]`")),
1166 "panic_implementation",
1167 "this attribute was renamed to `panic_handler`",
1168 cfg_fn!(panic_implementation))),
1171 ("panic_handler", Normal, Ungated),
1173 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1174 "alloc_error_handler",
1175 "#[alloc_error_handler] is an unstable feature",
1176 cfg_fn!(alloc_error_handler))),
1178 // Crate level attributes
1179 ("crate_name", CrateLevel, Ungated),
1180 ("crate_type", CrateLevel, Ungated),
1181 ("crate_id", CrateLevel, Ungated),
1182 ("feature", CrateLevel, Ungated),
1183 ("no_start", CrateLevel, Ungated),
1184 ("no_main", CrateLevel, Ungated),
1185 ("no_builtins", CrateLevel, Ungated),
1186 ("recursion_limit", CrateLevel, Ungated),
1187 ("type_length_limit", CrateLevel, Ungated),
1188 ("test_runner", CrateLevel, Gated(Stability::Unstable,
1189 "custom_test_frameworks",
1190 EXPLAIN_CUSTOM_TEST_FRAMEWORKS,
1191 cfg_fn!(custom_test_frameworks))),
1194 // cfg(...)'s that are feature gated
1195 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1196 // (name in cfg, feature, function to check if the feature is enabled)
1197 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1198 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1199 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1200 ("rustdoc", "doc_cfg", cfg_fn!(doc_cfg)),
1204 pub struct GatedCfg {
1210 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1211 let name = cfg.name().as_str();
1213 .position(|info| info.0 == name)
1222 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1223 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1224 if !has_feature(features) && !self.span.allows_unstable() {
1225 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1226 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1231 struct Context<'a> {
1232 features: &'a Features,
1233 parse_sess: &'a ParseSess,
1234 plugin_attributes: &'a [(String, AttributeType)],
1237 macro_rules! gate_feature_fn {
1238 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1239 let (cx, has_feature, span,
1240 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1241 let has_feature: bool = has_feature(&$cx.features);
1242 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1243 if !has_feature && !span.allows_unstable() {
1244 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1250 macro_rules! gate_feature {
1251 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1252 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1253 stringify!($feature), $explain, GateStrength::Hard)
1255 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1256 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1257 stringify!($feature), $explain, $level)
1261 impl<'a> Context<'a> {
1262 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1263 debug!("check_attribute(attr = {:?})", attr);
1264 let name = attr.name().as_str();
1265 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1267 if let Gated(_, name, desc, ref has_feature) = *gateage {
1268 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1269 } else if name == "doc" {
1270 if let Some(content) = attr.meta_item_list() {
1271 if content.iter().any(|c| c.check_name("include")) {
1272 gate_feature!(self, external_doc, attr.span,
1273 "#[doc(include = \"...\")] is experimental"
1278 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1282 for &(ref n, ref ty) in self.plugin_attributes {
1283 if attr.path == &**n {
1284 // Plugins can't gate attributes, so we don't check for it
1285 // unlike the code above; we only use this loop to
1286 // short-circuit to avoid the checks below
1287 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1291 if name.starts_with("rustc_") {
1292 gate_feature!(self, rustc_attrs, attr.span,
1293 "unless otherwise specified, attributes \
1294 with the prefix `rustc_` \
1295 are reserved for internal compiler diagnostics");
1296 } else if name.starts_with("derive_") {
1297 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1298 } else if !attr::is_known(attr) {
1299 // Only run the custom attribute lint during regular
1300 // feature gate checking. Macro gating runs
1301 // before the plugin attributes are registered
1302 // so we skip this then
1304 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1305 may have meaning added to it in the future", attr.path);
1306 gate_feature!(self, custom_attribute, attr.span, &msg);
1312 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1313 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1314 cx.check_attribute(attr, true);
1317 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1318 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1320 // FIXME (#28244): enforce that active features have issue numbers
1321 // assert!(issue.is_some())
1324 // search in Accepted, Removed, or Stable Removed features
1325 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1326 .find(|t| t.0 == feature);
1328 Some(&(_, _, issue, _)) => issue,
1329 None => panic!("Feature `{}` is not declared anywhere", feature),
1334 pub enum GateIssue {
1336 Library(Option<u32>)
1339 #[derive(Debug, Copy, Clone, PartialEq)]
1340 pub enum GateStrength {
1341 /// A hard error. (Most feature gates should use this.)
1343 /// Only a warning. (Use this only as backwards-compatibility demands.)
1347 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1349 feature_err(sess, feature, span, issue, explain).emit();
1352 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1353 explain: &str) -> DiagnosticBuilder<'a> {
1354 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1357 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1358 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1359 let diag = &sess.span_diagnostic;
1361 let issue = match issue {
1362 GateIssue::Language => find_lang_feature_issue(feature),
1363 GateIssue::Library(lib) => lib,
1366 let explanation = match issue {
1367 None | Some(0) => explain.to_owned(),
1368 Some(n) => format!("{} (see issue #{})", explain, n)
1371 let mut err = match level {
1372 GateStrength::Hard => {
1373 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1375 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1378 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1379 if sess.unstable_features.is_nightly_build() {
1380 err.help(&format!("add #![feature({})] to the \
1381 crate attributes to enable",
1385 // If we're on stable and only emitting a "soft" warning, add a note to
1386 // clarify that the feature isn't "on" (rather than being on but
1388 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1389 err.help("a nightly build of the compiler is required to enable this feature");
1396 const EXPLAIN_BOX_SYNTAX: &'static str =
1397 "box expression syntax is experimental; you can call `Box::new` instead.";
1399 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1400 "attributes on expressions are experimental.";
1402 pub const EXPLAIN_ASM: &'static str =
1403 "inline assembly is not stable enough for use and is subject to change";
1405 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1406 "`global_asm!` is not stable enough for use and is subject to change";
1408 pub const EXPLAIN_CUSTOM_TEST_FRAMEWORKS: &'static str =
1409 "custom test frameworks are an unstable feature";
1411 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1412 "`log_syntax!` is not stable enough for use and is subject to change";
1414 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1415 "`concat_idents` is not stable enough for use and is subject to change";
1417 pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
1418 "`format_args_nl` is only for internal language use and is subject to change";
1420 pub const EXPLAIN_TRACE_MACROS: &'static str =
1421 "`trace_macros` is not stable enough for use and is subject to change";
1422 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1423 "allow_internal_unstable side-steps feature gating and stability checks";
1424 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1425 "allow_internal_unsafe side-steps the unsafe_code lint";
1427 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1428 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1430 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1431 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1432 Prefer using procedural macro custom derive.";
1434 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1435 "attributes of the form `#[derive_*]` are reserved for the compiler";
1437 pub const EXPLAIN_LITERAL_MATCHER: &'static str =
1438 ":literal fragment specifier is experimental and subject to change";
1440 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1441 "unsized tuple coercion is not stable enough for use and is subject to change";
1443 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
1444 "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1446 struct PostExpansionVisitor<'a> {
1447 context: &'a Context<'a>,
1450 macro_rules! gate_feature_post {
1451 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1452 let (cx, span) = ($cx, $span);
1453 if !span.allows_unstable() {
1454 gate_feature!(cx.context, $feature, span, $explain)
1457 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1458 let (cx, span) = ($cx, $span);
1459 if !span.allows_unstable() {
1460 gate_feature!(cx.context, $feature, span, $explain, $level)
1465 impl<'a> PostExpansionVisitor<'a> {
1466 fn check_abi(&self, abi: Abi, span: Span) {
1468 Abi::RustIntrinsic => {
1469 gate_feature_post!(&self, intrinsics, span,
1470 "intrinsics are subject to change");
1472 Abi::PlatformIntrinsic => {
1473 gate_feature_post!(&self, platform_intrinsics, span,
1474 "platform intrinsics are experimental and possibly buggy");
1476 Abi::Vectorcall => {
1477 gate_feature_post!(&self, abi_vectorcall, span,
1478 "vectorcall is experimental and subject to change");
1481 gate_feature_post!(&self, abi_thiscall, span,
1482 "thiscall is experimental and subject to change");
1485 gate_feature_post!(&self, unboxed_closures, span,
1486 "rust-call ABI is subject to change");
1489 gate_feature_post!(&self, abi_ptx, span,
1490 "PTX ABIs are experimental and subject to change");
1492 Abi::Unadjusted => {
1493 gate_feature_post!(&self, abi_unadjusted, span,
1494 "unadjusted ABI is an implementation detail and perma-unstable");
1496 Abi::Msp430Interrupt => {
1497 gate_feature_post!(&self, abi_msp430_interrupt, span,
1498 "msp430-interrupt ABI is experimental and subject to change");
1500 Abi::X86Interrupt => {
1501 gate_feature_post!(&self, abi_x86_interrupt, span,
1502 "x86-interrupt ABI is experimental and subject to change");
1504 Abi::AmdGpuKernel => {
1505 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1506 "amdgpu-kernel ABI is experimental and subject to change");
1522 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1523 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1524 if !attr.span.allows_unstable() {
1525 // check for gated attributes
1526 self.context.check_attribute(attr, false);
1529 if attr.check_name("doc") {
1530 if let Some(content) = attr.meta_item_list() {
1531 if content.len() == 1 && content[0].check_name("cfg") {
1532 gate_feature_post!(&self, doc_cfg, attr.span,
1533 "#[doc(cfg(...))] is experimental"
1535 } else if content.iter().any(|c| c.check_name("masked")) {
1536 gate_feature_post!(&self, doc_masked, attr.span,
1537 "#[doc(masked)] is experimental"
1539 } else if content.iter().any(|c| c.check_name("spotlight")) {
1540 gate_feature_post!(&self, doc_spotlight, attr.span,
1541 "#[doc(spotlight)] is experimental"
1543 } else if content.iter().any(|c| c.check_name("alias")) {
1544 gate_feature_post!(&self, doc_alias, attr.span,
1545 "#[doc(alias = \"...\")] is experimental"
1547 } else if content.iter().any(|c| c.check_name("keyword")) {
1548 gate_feature_post!(&self, doc_keyword, attr.span,
1549 "#[doc(keyword = \"...\")] is experimental"
1555 if !self.context.features.unrestricted_attribute_tokens {
1556 // Unfortunately, `parse_meta` cannot be called speculatively
1557 // because it can report errors by itself, so we have to call it
1558 // only if the feature is disabled.
1559 if let Err(mut err) = attr.parse_meta(self.context.parse_sess) {
1560 err.help("try enabling `#![feature(unrestricted_attribute_tokens)]`").emit()
1565 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1566 if !name.as_str().is_ascii() {
1567 gate_feature_post!(&self,
1569 self.context.parse_sess.source_map().def_span(sp),
1570 "non-ascii idents are not fully supported.");
1574 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1575 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1576 if ident.name == "_" {
1577 gate_feature_post!(&self, underscore_imports, use_tree.span,
1578 "renaming imports with `_` is unstable");
1582 visit::walk_use_tree(self, use_tree, id);
1585 fn visit_item(&mut self, i: &'a ast::Item) {
1587 ast::ItemKind::ExternCrate(_) => {
1588 if i.ident.name == "_" {
1589 gate_feature_post!(&self, underscore_imports, i.span,
1590 "renaming extern crates with `_` is unstable");
1594 ast::ItemKind::ForeignMod(ref foreign_module) => {
1595 self.check_abi(foreign_module.abi, i.span);
1598 ast::ItemKind::Fn(..) => {
1599 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1600 gate_feature_post!(&self, plugin_registrar, i.span,
1601 "compiler plugins are experimental and possibly buggy");
1603 if attr::contains_name(&i.attrs[..], "start") {
1604 gate_feature_post!(&self, start, i.span,
1605 "a #[start] function is an experimental \
1606 feature whose signature may change \
1609 if attr::contains_name(&i.attrs[..], "main") {
1610 gate_feature_post!(&self, main, i.span,
1611 "declaration of a nonstandard #[main] \
1612 function may change over time, for now \
1613 a top-level `fn main()` is required");
1617 ast::ItemKind::Struct(..) => {
1618 if let Some(attr) = attr::find_by_name(&i.attrs[..], "repr") {
1619 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1620 if item.check_name("simd") {
1621 gate_feature_post!(&self, repr_simd, attr.span,
1622 "SIMD types are experimental and possibly buggy");
1624 if let Some((name, _)) = item.name_value_literal() {
1625 if name == "packed" {
1626 gate_feature_post!(&self, repr_packed, attr.span,
1627 "the `#[repr(packed(n))]` attribute \
1635 ast::ItemKind::TraitAlias(..) => {
1636 gate_feature_post!(&self, trait_alias,
1638 "trait aliases are not yet fully implemented");
1641 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1642 if polarity == ast::ImplPolarity::Negative {
1643 gate_feature_post!(&self, optin_builtin_traits,
1645 "negative trait bounds are not yet fully implemented; \
1646 use marker types for now");
1649 if let ast::Defaultness::Default = defaultness {
1650 gate_feature_post!(&self, specialization,
1652 "specialization is unstable");
1656 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1657 gate_feature_post!(&self, optin_builtin_traits,
1659 "auto traits are experimental and possibly buggy");
1662 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1663 let msg = "`macro` is experimental";
1664 gate_feature_post!(&self, decl_macro, i.span, msg);
1667 ast::ItemKind::Existential(..) => {
1672 "existential types are unstable"
1679 visit::walk_item(self, i);
1682 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1684 ast::ForeignItemKind::Fn(..) |
1685 ast::ForeignItemKind::Static(..) => {
1686 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1687 let links_to_llvm = match link_name {
1688 Some(val) => val.as_str().starts_with("llvm."),
1692 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1693 "linking to LLVM intrinsics is experimental");
1696 ast::ForeignItemKind::Ty => {
1697 gate_feature_post!(&self, extern_types, i.span,
1698 "extern types are experimental");
1700 ast::ForeignItemKind::Macro(..) => {}
1703 visit::walk_foreign_item(self, i)
1706 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1708 ast::TyKind::BareFn(ref bare_fn_ty) => {
1709 self.check_abi(bare_fn_ty.abi, ty.span);
1711 ast::TyKind::Never => {
1712 gate_feature_post!(&self, never_type, ty.span,
1713 "The `!` type is experimental");
1717 visit::walk_ty(self, ty)
1720 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1721 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1722 if let ast::TyKind::Never = output_ty.node {
1725 self.visit_ty(output_ty)
1730 fn visit_expr(&mut self, e: &'a ast::Expr) {
1732 ast::ExprKind::Box(_) => {
1733 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1735 ast::ExprKind::Type(..) => {
1736 gate_feature_post!(&self, type_ascription, e.span,
1737 "type ascription is experimental");
1739 ast::ExprKind::ObsoleteInPlace(..) => {
1740 // these get a hard error in ast-validation
1742 ast::ExprKind::Yield(..) => {
1743 gate_feature_post!(&self, generators,
1745 "yield syntax is experimental");
1747 ast::ExprKind::TryBlock(_) => {
1748 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
1750 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1752 gate_feature_post!(&self, if_while_or_patterns, e.span,
1753 "multiple patterns in `if let` and `while let` are unstable");
1756 ast::ExprKind::Block(_, opt_label) => {
1757 if let Some(label) = opt_label {
1758 gate_feature_post!(&self, label_break_value, label.ident.span,
1759 "labels on blocks are unstable");
1762 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1763 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1765 ast::ExprKind::Async(..) => {
1766 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1770 visit::walk_expr(self, e);
1773 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1774 visit::walk_arm(self, arm)
1777 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1778 match pattern.node {
1779 PatKind::Slice(_, Some(ref subslice), _) => {
1780 gate_feature_post!(&self, slice_patterns,
1782 "syntax for subslices in slice patterns is not yet stabilized");
1784 PatKind::Box(..) => {
1785 gate_feature_post!(&self, box_patterns,
1787 "box pattern syntax is experimental");
1789 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1790 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1791 "exclusive range pattern syntax is experimental");
1795 visit::walk_pat(self, pattern)
1798 fn visit_fn(&mut self,
1799 fn_kind: FnKind<'a>,
1800 fn_decl: &'a ast::FnDecl,
1804 FnKind::ItemFn(_, header, _, _) => {
1805 // check for const fn and async fn declarations
1806 if header.asyncness.is_async() {
1807 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1809 if header.constness.node == ast::Constness::Const {
1810 gate_feature_post!(&self, min_const_fn, span, "const fn is unstable");
1812 // stability of const fn methods are covered in
1813 // visit_trait_item and visit_impl_item below; this is
1814 // because default methods don't pass through this
1817 self.check_abi(header.abi, span);
1819 FnKind::Method(_, sig, _, _) => {
1820 self.check_abi(sig.header.abi, span);
1824 visit::walk_fn(self, fn_kind, fn_decl, span);
1827 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1829 ast::TraitItemKind::Method(ref sig, ref block) => {
1830 if block.is_none() {
1831 self.check_abi(sig.header.abi, ti.span);
1833 if sig.header.constness.node == ast::Constness::Const {
1834 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1837 ast::TraitItemKind::Type(_, ref default) => {
1838 // We use three if statements instead of something like match guards so that all
1839 // of these errors can be emitted if all cases apply.
1840 if default.is_some() {
1841 gate_feature_post!(&self, associated_type_defaults, ti.span,
1842 "associated type defaults are unstable");
1844 if !ti.generics.params.is_empty() {
1845 gate_feature_post!(&self, generic_associated_types, ti.span,
1846 "generic associated types are unstable");
1848 if !ti.generics.where_clause.predicates.is_empty() {
1849 gate_feature_post!(&self, generic_associated_types, ti.span,
1850 "where clauses on associated types are unstable");
1855 visit::walk_trait_item(self, ti);
1858 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1859 if ii.defaultness == ast::Defaultness::Default {
1860 gate_feature_post!(&self, specialization,
1862 "specialization is unstable");
1866 ast::ImplItemKind::Method(ref sig, _) => {
1867 if sig.header.constness.node == ast::Constness::Const {
1868 gate_feature_post!(&self, min_const_fn, ii.span, "const fn is unstable");
1871 ast::ImplItemKind::Existential(..) => {
1876 "existential types are unstable"
1879 ast::ImplItemKind::Type(_) => {
1880 if !ii.generics.params.is_empty() {
1881 gate_feature_post!(&self, generic_associated_types, ii.span,
1882 "generic associated types are unstable");
1884 if !ii.generics.where_clause.predicates.is_empty() {
1885 gate_feature_post!(&self, generic_associated_types, ii.span,
1886 "where clauses on associated types are unstable");
1891 visit::walk_impl_item(self, ii);
1894 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1895 for segment in &path.segments {
1896 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1897 // For such macros identifiers must have empty context, because this context is
1898 // used during name resolution and produced names must be unhygienic for compatibility.
1899 // On the other hand, we need the actual non-empty context for feature gate checking
1900 // because it's hygienic even for legacy macros. As previously stated, such context
1901 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1902 // there while keeping location info from the ident span.
1903 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1904 if segment.ident.name == keywords::Extern.name() {
1905 gate_feature_post!(&self, extern_in_paths, span,
1906 "`extern` in paths is experimental");
1910 visit::walk_path(self, path);
1913 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1914 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1915 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1916 "`crate` visibility modifier is experimental");
1918 visit::walk_vis(self, vis);
1922 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1923 crate_edition: Edition) -> Features {
1924 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1925 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1926 if let Some(reason) = reason {
1927 err.span_note(span, reason);
1932 // Some features are known to be incomplete and using them is likely to have
1933 // unanticipated results, such as compiler crashes. We warn the user about these
1935 let incomplete_features = ["generic_associated_types"];
1937 let mut features = Features::new();
1938 let mut edition_enabled_features = FxHashMap();
1940 for &edition in ALL_EDITIONS {
1941 if edition <= crate_edition {
1942 // The `crate_edition` implies its respective umbrella feature-gate
1943 // (i.e. `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
1944 edition_enabled_features.insert(Symbol::intern(edition.feature_name()), edition);
1948 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1949 if let Some(f_edition) = f_edition {
1950 if f_edition <= crate_edition {
1951 set(&mut features, DUMMY_SP);
1952 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1957 // Process the edition umbrella feature-gates first, to ensure
1958 // `edition_enabled_features` is completed before it's queried.
1959 for attr in krate_attrs {
1960 if !attr.check_name("feature") {
1964 let list = match attr.meta_item_list() {
1970 let name = if let Some(word) = mi.word() {
1976 if incomplete_features.iter().any(|f| *f == name.as_str()) {
1977 span_handler.struct_span_warn(
1980 "the feature `{}` is incomplete and may cause the compiler to crash",
1986 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1987 if *edition <= crate_edition {
1991 for &(name, .., f_edition, set) in ACTIVE_FEATURES {
1992 if let Some(f_edition) = f_edition {
1993 if f_edition <= *edition {
1994 // FIXME(Manishearth) there is currently no way to set
1995 // lib features by edition
1996 set(&mut features, DUMMY_SP);
1997 edition_enabled_features.insert(Symbol::intern(name), *edition);
2005 for attr in krate_attrs {
2006 if !attr.check_name("feature") {
2010 let list = match attr.meta_item_list() {
2013 span_err!(span_handler, attr.span, E0555,
2014 "malformed feature attribute, expected #![feature(...)]");
2020 let name = if let Some(word) = mi.word() {
2023 span_err!(span_handler, mi.span, E0556,
2024 "malformed feature, expected just one word");
2028 if let Some(edition) = edition_enabled_features.get(&name) {
2033 "the feature `{}` is included in the Rust {} edition",
2040 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
2041 // Handled in the separate loop above.
2045 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
2046 set(&mut features, mi.span);
2047 features.declared_lang_features.push((name, mi.span, None));
2051 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
2052 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
2053 if let Some((.., reason)) = removed.or(stable_removed) {
2054 feature_removed(span_handler, mi.span, *reason);
2058 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
2059 let since = Some(Symbol::intern(since));
2060 features.declared_lang_features.push((name, mi.span, since));
2064 features.declared_lib_features.push((name, mi.span));
2071 pub fn check_crate(krate: &ast::Crate,
2073 features: &Features,
2074 plugin_attributes: &[(String, AttributeType)],
2075 unstable: UnstableFeatures) {
2076 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2083 let visitor = &mut PostExpansionVisitor { context: &ctx };
2084 visit::walk_crate(visitor, krate);
2087 #[derive(Clone, Copy, Hash)]
2088 pub enum UnstableFeatures {
2089 /// Hard errors for unstable features are active, as on
2090 /// beta/stable channels.
2092 /// Allow features to be activated, as on nightly.
2094 /// Errors are bypassed for bootstrapping. This is required any time
2095 /// during the build that feature-related lints are set to warn or above
2096 /// because the build turns on warnings-as-errors and uses lots of unstable
2097 /// features. As a result, this is always required for building Rust itself.
2101 impl UnstableFeatures {
2102 pub fn from_environment() -> UnstableFeatures {
2103 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2104 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2105 // Whether we should enable unstable features for bootstrapping
2106 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2107 match (disable_unstable_features, bootstrap) {
2108 (_, true) => UnstableFeatures::Cheat,
2109 (true, _) => UnstableFeatures::Disallow,
2110 (false, _) => UnstableFeatures::Allow
2114 pub fn is_nightly_build(&self) -> bool {
2116 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2122 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2123 unstable: UnstableFeatures) {
2124 let allow_features = match unstable {
2125 UnstableFeatures::Allow => true,
2126 UnstableFeatures::Disallow => false,
2127 UnstableFeatures::Cheat => true
2129 if !allow_features {
2130 for attr in &krate.attrs {
2131 if attr.check_name("feature") {
2132 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2133 span_err!(span_handler, attr.span, E0554,
2134 "#![feature] may not be used on the {} release channel",