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};
33 use edition::{ALL_EDITIONS, Edition};
34 use syntax_pos::{Span, DUMMY_SP};
35 use errors::{DiagnosticBuilder, Handler, FatalError};
36 use visit::{self, FnKind, Visitor};
38 use symbol::{keywords, Symbol};
44 fn f(features: &mut Features, _: Span) {
45 features.$field = true;
47 f as fn(&mut Features, Span)
51 macro_rules! declare_features {
52 ($((active, $feature: ident, $ver: expr, $issue: expr, $edition: expr),)+) => {
53 /// Represents active features that are currently being implemented or
54 /// currently being considered for addition/removal.
55 const ACTIVE_FEATURES:
56 &'static [(&'static str, &'static str, Option<u32>,
57 Option<Edition>, fn(&mut Features, Span))] =
58 &[$((stringify!($feature), $ver, $issue, $edition, set!($feature))),+];
60 /// A set of features to be used by later passes.
63 /// `#![feature]` attrs for language features, for error reporting
64 pub declared_lang_features: Vec<(Symbol, Span, Option<Symbol>)>,
65 /// `#![feature]` attrs for non-language (library) features
66 pub declared_lib_features: Vec<(Symbol, Span)>,
67 $(pub $feature: bool),+
71 pub fn new() -> Features {
73 declared_lang_features: Vec::new(),
74 declared_lib_features: Vec::new(),
79 pub fn walk_feature_fields<F>(&self, mut f: F)
80 where F: FnMut(&str, bool)
82 $(f(stringify!($feature), self.$feature);)+
85 pub fn use_extern_macros(&self) -> bool {
86 // The `decl_macro` and `tool_attributes` features imply `use_extern_macros`.
87 self.use_extern_macros || self.decl_macro || self.tool_attributes
92 ($((removed, $feature: ident, $ver: expr, $issue: expr, None, $reason: expr),)+) => {
93 /// Represents unstable features which have since been removed (it was once Active)
94 const REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
95 $((stringify!($feature), $ver, $issue, $reason)),+
99 ($((stable_removed, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
100 /// Represents stable features which have since been removed (it was once Accepted)
101 const STABLE_REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
102 $((stringify!($feature), $ver, $issue, None)),+
106 ($((accepted, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
107 /// Those language feature has since been Accepted (it was once Active)
108 const ACCEPTED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
109 $((stringify!($feature), $ver, $issue, None)),+
114 // If you change this, please modify src/doc/unstable-book as well.
116 // Don't ever remove anything from this list; set them to 'Removed'.
118 // The version numbers here correspond to the version in which the current status
119 // was set. This is most important for knowing when a particular feature became
122 // NB: tools/tidy/src/features.rs parses this information directly out of the
123 // source, so take care when modifying it.
126 (active, asm, "1.0.0", Some(29722), None),
127 (active, concat_idents, "1.0.0", Some(29599), None),
128 (active, link_args, "1.0.0", Some(29596), None),
129 (active, log_syntax, "1.0.0", Some(29598), None),
130 (active, non_ascii_idents, "1.0.0", Some(28979), None),
131 (active, plugin_registrar, "1.0.0", Some(29597), None),
132 (active, thread_local, "1.0.0", Some(29594), None),
133 (active, trace_macros, "1.0.0", Some(29598), None),
135 // rustc internal, for now:
136 (active, intrinsics, "1.0.0", None, None),
137 (active, lang_items, "1.0.0", None, None),
138 (active, format_args_nl, "1.29.0", None, None),
140 (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
141 (active, linkage, "1.0.0", Some(29603), None),
142 (active, quote, "1.0.0", Some(29601), None),
145 (active, rustc_diagnostic_macros, "1.0.0", None, None),
146 (active, rustc_const_unstable, "1.0.0", None, None),
147 (active, box_syntax, "1.0.0", Some(49733), None),
148 (active, unboxed_closures, "1.0.0", Some(29625), None),
150 (active, fundamental, "1.0.0", Some(29635), None),
151 (active, main, "1.0.0", Some(29634), None),
152 (active, needs_allocator, "1.4.0", Some(27389), None),
153 (active, on_unimplemented, "1.0.0", Some(29628), None),
154 (active, plugin, "1.0.0", Some(29597), None),
155 (active, simd_ffi, "1.0.0", Some(27731), None),
156 (active, start, "1.0.0", Some(29633), None),
157 (active, structural_match, "1.8.0", Some(31434), None),
158 (active, panic_runtime, "1.10.0", Some(32837), None),
159 (active, needs_panic_runtime, "1.10.0", Some(32837), None),
161 // OIBIT specific features
162 (active, optin_builtin_traits, "1.0.0", Some(13231), None),
164 // Allows use of #[staged_api]
166 (active, staged_api, "1.0.0", None, None),
168 // Allows using #![no_core]
169 (active, no_core, "1.3.0", Some(29639), None),
171 // Allows using `box` in patterns; RFC 469
172 (active, box_patterns, "1.0.0", Some(29641), None),
174 // Allows using the unsafe_destructor_blind_to_params attribute;
176 (active, dropck_parametricity, "1.3.0", Some(28498), None),
178 // Allows using the may_dangle attribute; RFC 1327
179 (active, dropck_eyepatch, "1.10.0", Some(34761), None),
181 // Allows the use of custom attributes; RFC 572
182 (active, custom_attribute, "1.0.0", Some(29642), None),
184 // Allows the use of #[derive(Anything)] as sugar for
185 // #[derive_Anything].
186 (active, custom_derive, "1.0.0", Some(29644), None),
188 // Allows the use of rustc_* attributes; RFC 572
189 (active, rustc_attrs, "1.0.0", Some(29642), None),
191 // Allows the use of non lexical lifetimes; RFC 2094
192 (active, nll, "1.0.0", Some(43234), None),
194 // Allows the use of #[allow_internal_unstable]. This is an
195 // attribute on macro_rules! and can't use the attribute handling
196 // below (it has to be checked before expansion possibly makes
197 // macros disappear).
200 (active, allow_internal_unstable, "1.0.0", None, None),
202 // Allows the use of #[allow_internal_unsafe]. This is an
203 // attribute on macro_rules! and can't use the attribute handling
204 // below (it has to be checked before expansion possibly makes
205 // macros disappear).
208 (active, allow_internal_unsafe, "1.0.0", None, None),
210 // #23121. Array patterns have some hazards yet.
211 (active, slice_patterns, "1.0.0", Some(23121), None),
213 // Allows the definition of `const fn` functions.
214 (active, const_fn, "1.2.0", Some(24111), None),
216 // Allows let bindings and destructuring in `const fn` functions and constants.
217 (active, const_let, "1.22.1", Some(48821), None),
219 // Allows using #[prelude_import] on glob `use` items.
222 (active, prelude_import, "1.2.0", None, None),
224 // Allows default type parameters to influence type inference.
225 (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
227 // Allows associated type defaults
228 (active, associated_type_defaults, "1.2.0", Some(29661), None),
230 // allow `repr(simd)`, and importing the various simd intrinsics
231 (active, repr_simd, "1.4.0", Some(27731), None),
233 // allow `extern "platform-intrinsic" { ... }`
234 (active, platform_intrinsics, "1.4.0", Some(27731), None),
236 // allow `#[unwind(..)]`
237 // rustc internal for rust runtime
238 (active, unwind_attributes, "1.4.0", None, None),
240 // allow the use of `#[naked]` on functions.
241 (active, naked_functions, "1.9.0", Some(32408), None),
243 // allow `#[no_debug]`
244 (active, no_debug, "1.5.0", Some(29721), None),
246 // allow `#[omit_gdb_pretty_printer_section]`
248 (active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
250 // Allows cfg(target_vendor = "...").
251 (active, cfg_target_vendor, "1.5.0", Some(29718), None),
253 // Allow attributes on expressions and non-item statements
254 (active, stmt_expr_attributes, "1.6.0", Some(15701), None),
256 // allow using type ascription in expressions
257 (active, type_ascription, "1.6.0", Some(23416), None),
259 // Allows cfg(target_thread_local)
260 (active, cfg_target_thread_local, "1.7.0", Some(29594), None),
263 (active, abi_vectorcall, "1.7.0", None, None),
266 (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
268 // impl specialization (RFC 1210)
269 (active, specialization, "1.7.0", Some(31844), None),
271 // Allows cfg(target_has_atomic = "...").
272 (active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
274 // The `!` type. Does not imply exhaustive_patterns (below) any more.
275 (active, never_type, "1.13.0", Some(35121), None),
277 // Allows exhaustive pattern matching on types that contain uninhabited types.
278 (active, exhaustive_patterns, "1.13.0", Some(51085), None),
280 // Allows all literals in attribute lists and values of key-value pairs.
281 (active, attr_literals, "1.13.0", Some(34981), None),
283 // Allows untagged unions `union U { ... }`
284 (active, untagged_unions, "1.13.0", Some(32836), None),
286 // Used to identify the `compiler_builtins` crate
288 (active, compiler_builtins, "1.13.0", None, None),
290 // Allows #[link(..., cfg(..))]
291 (active, link_cfg, "1.14.0", Some(37406), None),
293 (active, use_extern_macros, "1.15.0", Some(35896), Some(Edition::Edition2018)),
295 // `extern "ptx-*" fn()`
296 (active, abi_ptx, "1.15.0", Some(38788), None),
298 // The `repr(i128)` annotation for enums
299 (active, repr128, "1.16.0", Some(35118), None),
301 // The `unadjusted` ABI. Perma unstable.
303 (active, abi_unadjusted, "1.16.0", None, None),
305 // Declarative macros 2.0 (`macro`).
306 (active, decl_macro, "1.17.0", Some(39412), None),
308 // Allows #[link(kind="static-nobundle"...)]
309 (active, static_nobundle, "1.16.0", Some(37403), None),
311 // `extern "msp430-interrupt" fn()`
312 (active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
314 // Used to identify crates that contain sanitizer runtimes
316 (active, sanitizer_runtime, "1.17.0", None, None),
318 // Used to identify crates that contain the profiler runtime
320 (active, profiler_runtime, "1.18.0", None, None),
322 // `extern "x86-interrupt" fn()`
323 (active, abi_x86_interrupt, "1.17.0", Some(40180), None),
325 // Allows the `catch {...}` expression
326 (active, catch_expr, "1.17.0", Some(31436), None),
328 // Used to preserve symbols (see llvm.used)
329 (active, used, "1.18.0", Some(40289), None),
331 // Allows module-level inline assembly by way of global_asm!()
332 (active, global_asm, "1.18.0", Some(35119), None),
334 // Allows overlapping impls of marker traits
335 (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
337 // Allows use of the :vis macro fragment specifier
338 (active, macro_vis_matcher, "1.18.0", Some(41022), None),
341 (active, abi_thiscall, "1.19.0", None, None),
343 // Allows a test to fail without failing the whole suite
344 (active, allow_fail, "1.19.0", Some(42219), None),
346 // Allows unsized tuple coercion.
347 (active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
350 (active, generators, "1.21.0", Some(43122), None),
353 (active, trait_alias, "1.24.0", Some(41517), None),
356 (active, allocator_internals, "1.20.0", None, None),
359 (active, doc_cfg, "1.21.0", Some(43781), None),
361 (active, doc_masked, "1.21.0", Some(44027), None),
363 (active, doc_spotlight, "1.22.0", Some(45040), None),
364 // #[doc(include="some-file")]
365 (active, external_doc, "1.22.0", Some(44732), None),
367 // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
368 (active, non_exhaustive, "1.22.0", Some(44109), None),
370 // `crate` as visibility modifier, synonymous to `pub(crate)`
371 (active, crate_visibility_modifier, "1.23.0", Some(45388), Some(Edition::Edition2018)),
374 (active, extern_types, "1.23.0", Some(43467), None),
376 // Allow trait methods with arbitrary self types
377 (active, arbitrary_self_types, "1.23.0", Some(44874), None),
380 (active, crate_in_paths, "1.23.0", Some(45477), Some(Edition::Edition2018)),
382 // In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
383 (active, in_band_lifetimes, "1.23.0", Some(44524), None),
385 // generic associated types (RFC 1598)
386 (active, generic_associated_types, "1.23.0", Some(44265), None),
388 // Resolve absolute paths as paths from other crates
389 (active, extern_absolute_paths, "1.24.0", Some(44660), Some(Edition::Edition2018)),
391 // `foo.rs` as an alternative to `foo/mod.rs`
392 (active, non_modrs_mods, "1.24.0", Some(44660), Some(Edition::Edition2018)),
395 (active, extern_in_paths, "1.23.0", Some(44660), None),
397 // Use `?` as the Kleene "at most one" operator
398 (active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
400 // Infer outlives requirements; RFC 2093
401 (active, infer_outlives_requirements, "1.26.0", Some(44493), None),
403 // Infer static outlives requirements; RFC 2093
404 (active, infer_static_outlives_requirements, "1.26.0", Some(44493), None),
406 // Multiple patterns with `|` in `if let` and `while let`
407 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
409 // Parentheses in patterns
410 (active, pattern_parentheses, "1.26.0", Some(51087), None),
412 // Allows `#[repr(packed)]` attribute on structs
413 (active, repr_packed, "1.26.0", Some(33158), None),
415 // `use path as _;` and `extern crate c as _;`
416 (active, underscore_imports, "1.26.0", Some(48216), None),
418 // Allows keywords to be escaped for use as identifiers
419 (active, raw_identifiers, "1.26.0", Some(48589), Some(Edition::Edition2018)),
421 // Allows macro invocations in `extern {}` blocks
422 (active, macros_in_extern, "1.27.0", Some(49476), None),
424 // `existential type`
425 (active, existential_type, "1.28.0", Some(34511), None),
427 // unstable #[target_feature] directives
428 (active, arm_target_feature, "1.27.0", Some(44839), None),
429 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
430 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
431 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
432 (active, mips_target_feature, "1.27.0", Some(44839), None),
433 (active, avx512_target_feature, "1.27.0", Some(44839), None),
434 (active, mmx_target_feature, "1.27.0", Some(44839), None),
435 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
436 (active, tbm_target_feature, "1.27.0", Some(44839), None),
438 // Allows macro invocations of the form `#[foo::bar]`
439 (active, proc_macro_path_invoc, "1.27.0", Some(38356), None),
441 // Allows macro invocations on modules expressions and statements and
442 // procedural macros to expand to non-items.
443 (active, proc_macro_mod, "1.27.0", Some(38356), None),
444 (active, proc_macro_expr, "1.27.0", Some(38356), None),
445 (active, proc_macro_non_items, "1.27.0", Some(38356), None),
446 (active, proc_macro_gen, "1.27.0", Some(38356), None),
448 // #[doc(alias = "...")]
449 (active, doc_alias, "1.27.0", Some(50146), None),
451 // Access to crate names passed via `--extern` through prelude
452 (active, extern_prelude, "1.27.0", Some(44660), Some(Edition::Edition2018)),
455 (active, tool_attributes, "1.25.0", Some(44690), None),
457 (active, tool_lints, "1.28.0", Some(44690), None),
459 // allow irrefutable patterns in if-let and while-let statements (RFC 2086)
460 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
462 // Allows use of the :literal macro fragment specifier (RFC 1576)
463 (active, macro_literal_matcher, "1.27.0", Some(35625), None),
465 // inconsistent bounds in where clauses
466 (active, trivial_bounds, "1.28.0", Some(48214), None),
469 (active, label_break_value, "1.28.0", Some(48594), None),
471 // #[panic_implementation]
472 (active, panic_implementation, "1.28.0", Some(44489), None),
474 // #[doc(keyword = "...")]
475 (active, doc_keyword, "1.28.0", Some(51315), None),
477 // Allows async and await syntax
478 (active, async_await, "1.28.0", Some(50547), None),
480 // #[alloc_error_handler]
481 (active, alloc_error_handler, "1.29.0", Some(51540), None),
483 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
485 // impl<I:Iterator> Iterator for &mut Iterator
486 // impl Debug for Foo<'_>
487 (active, impl_header_lifetime_elision, "1.30.0", Some(15872), Some(Edition::Edition2018)),
491 (removed, import_shadowing, "1.0.0", None, None, None),
492 (removed, managed_boxes, "1.0.0", None, None, None),
493 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
494 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
495 (removed, reflect, "1.0.0", Some(27749), None, None),
496 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
497 (removed, opt_out_copy, "1.0.0", None, None, None),
498 (removed, quad_precision_float, "1.0.0", None, None, None),
499 (removed, struct_inherit, "1.0.0", None, None, None),
500 (removed, test_removed_feature, "1.0.0", None, None, None),
501 (removed, visible_private_types, "1.0.0", None, None, None),
502 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
503 // Allows using items which are missing stability attributes
505 (removed, unmarked_api, "1.0.0", None, None, None),
506 (removed, pushpop_unsafe, "1.2.0", None, None, None),
507 (removed, allocator, "1.0.0", None, None, None),
508 (removed, simd, "1.0.0", Some(27731), None,
509 Some("removed in favor of `#[repr(simd)]`")),
510 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
511 Some("merged into `#![feature(slice_patterns)]`")),
512 (removed, macro_reexport, "1.0.0", Some(29638), None,
513 Some("subsumed by `#![feature(use_extern_macros)]` and `pub use`")),
517 (stable_removed, no_stack_check, "1.0.0", None, None),
521 (accepted, associated_types, "1.0.0", None, None),
522 // allow overloading augmented assignment operations like `a += b`
523 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
524 // allow empty structs and enum variants with braces
525 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
526 // Allows indexing into constant arrays.
527 (accepted, const_indexing, "1.26.0", Some(29947), None),
528 (accepted, default_type_params, "1.0.0", None, None),
529 (accepted, globs, "1.0.0", None, None),
530 (accepted, if_let, "1.0.0", None, None),
531 // A temporary feature gate used to enable parser extensions needed
532 // to bootstrap fix for #5723.
533 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
534 (accepted, macro_rules, "1.0.0", None, None),
535 // Allows using #![no_std]
536 (accepted, no_std, "1.6.0", None, None),
537 (accepted, slicing_syntax, "1.0.0", None, None),
538 (accepted, struct_variant, "1.0.0", None, None),
539 // These are used to test this portion of the compiler, they don't actually
541 (accepted, test_accepted_feature, "1.0.0", None, None),
542 (accepted, tuple_indexing, "1.0.0", None, None),
543 // Allows macros to appear in the type position.
544 (accepted, type_macros, "1.13.0", Some(27245), None),
545 (accepted, while_let, "1.0.0", None, None),
546 // Allows `#[deprecated]` attribute
547 (accepted, deprecated, "1.9.0", Some(29935), None),
549 (accepted, question_mark, "1.13.0", Some(31436), None),
550 // Allows `..` in tuple (struct) patterns
551 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
552 (accepted, item_like_imports, "1.15.0", Some(35120), None),
553 // Allows using `Self` and associated types in struct expressions and patterns.
554 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
555 // elide `'static` lifetimes in `static`s and `const`s
556 (accepted, static_in_const, "1.17.0", Some(35897), None),
557 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
558 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
559 // Allows the definition recursive static items.
560 (accepted, static_recursion, "1.17.0", Some(29719), None),
561 // pub(restricted) visibilities (RFC 1422)
562 (accepted, pub_restricted, "1.18.0", Some(32409), None),
563 // The #![windows_subsystem] attribute
564 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
565 // Allows `break {expr}` with a value inside `loop`s.
566 (accepted, loop_break_value, "1.19.0", Some(37339), None),
567 // Permits numeric fields in struct expressions and patterns.
568 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
569 // Coerces non capturing closures to function pointers
570 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
571 // Allows attributes on struct literal fields.
572 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
573 // Allows the definition of associated constants in `trait` or `impl`
575 (accepted, associated_consts, "1.20.0", Some(29646), None),
576 // Usage of the `compile_error!` macro
577 (accepted, compile_error, "1.20.0", Some(40872), None),
578 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
579 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
580 // Allow Drop types in constants (RFC 1440)
581 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
582 // Allows the sysV64 ABI to be specified on all platforms
583 // instead of just the platforms on which it is the C ABI
584 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
585 // Allows `repr(align(16))` struct attribute (RFC 1358)
586 (accepted, repr_align, "1.25.0", Some(33626), None),
587 // allow '|' at beginning of match arms (RFC 1925)
588 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
589 // Nested groups in `use` (RFC 2128)
590 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
592 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
593 // allow `..=` in patterns (RFC 1192)
594 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
595 // Termination trait in main (RFC 1937)
596 (accepted, termination_trait, "1.26.0", Some(43301), None),
597 // Copy/Clone closures (RFC 2132)
598 (accepted, clone_closures, "1.26.0", Some(44490), None),
599 (accepted, copy_closures, "1.26.0", Some(44490), None),
600 // Allows `impl Trait` in function arguments.
601 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
602 // Allows `impl Trait` in function return types.
603 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
605 (accepted, i128_type, "1.26.0", Some(35118), None),
606 // Default match binding modes (RFC 2005)
607 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
608 // allow `'_` placeholder lifetimes
609 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
610 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
611 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
612 // Allows cfg(target_feature = "...").
613 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
614 // Allows #[target_feature(...)]
615 (accepted, target_feature, "1.27.0", None, None),
616 // Trait object syntax with `dyn` prefix
617 (accepted, dyn_trait, "1.27.0", Some(44662), None),
618 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
619 (accepted, fn_must_use, "1.27.0", Some(43302), None),
620 // Allows use of the :lifetime macro fragment specifier
621 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
622 // Termination trait in tests (RFC 1937)
623 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
624 // The #[global_allocator] attribute
625 (accepted, global_allocator, "1.28.0", Some(27389), None),
626 // Allows `#[repr(transparent)]` attribute on newtype structs
627 (accepted, repr_transparent, "1.28.0", Some(43036), None),
628 // Defining procedural macros in `proc-macro` crates
629 (accepted, proc_macro, "1.29.0", Some(38356), None),
632 // If you change this, please modify src/doc/unstable-book as well. You must
633 // move that documentation into the relevant place in the other docs, and
634 // remove the chapter on the flag.
636 #[derive(Copy, Clone, PartialEq, Debug)]
637 pub enum AttributeType {
638 /// Normal, builtin attribute that is consumed
639 /// by the compiler before the unused_attribute check
642 /// Builtin attribute that may not be consumed by the compiler
643 /// before the unused_attribute check. These attributes
644 /// will be ignored by the unused_attribute lint
647 /// Builtin attribute that is only allowed at the crate level
651 pub enum AttributeGate {
652 /// Is gated by a given feature gate, reason
653 /// and function to check if enabled
654 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
656 /// Ungated attribute, can be used on all release channels
661 fn is_deprecated(&self) -> bool {
663 Gated(Stability::Deprecated(_), ..) => true,
669 #[derive(Copy, Clone, Debug)]
672 // Argument is tracking issue link.
673 Deprecated(&'static str),
677 impl ::std::fmt::Debug for AttributeGate {
678 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
680 Gated(ref stab, name, expl, _) =>
681 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
682 Ungated => write!(fmt, "Ungated")
687 macro_rules! cfg_fn {
688 ($field: ident) => {{
689 fn f(features: &Features) -> bool {
692 f as fn(&Features) -> bool
696 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
697 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
700 pub fn is_builtin_attr_name(name: ast::Name) -> bool {
701 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| name == builtin_name)
704 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
705 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.check_name(builtin_name)) ||
706 attr.name().as_str().starts_with("rustc_")
709 // Attributes that have a special meaning to rustc or rustdoc
710 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
713 ("warn", Normal, Ungated),
714 ("allow", Normal, Ungated),
715 ("forbid", Normal, Ungated),
716 ("deny", Normal, Ungated),
718 ("macro_use", Normal, Ungated),
719 ("macro_export", Normal, Ungated),
720 ("plugin_registrar", Normal, Ungated),
722 ("cfg", Normal, Ungated),
723 ("cfg_attr", Normal, Ungated),
724 ("main", Normal, Ungated),
725 ("start", Normal, Ungated),
726 ("test", Normal, Ungated),
727 ("bench", Normal, Ungated),
728 ("repr", Normal, Ungated),
729 ("path", Normal, Ungated),
730 ("abi", Normal, Ungated),
731 ("automatically_derived", Normal, Ungated),
732 ("no_mangle", Normal, Ungated),
733 ("no_link", Normal, Ungated),
734 ("derive", Normal, Ungated),
735 ("should_panic", Normal, Ungated),
736 ("ignore", Normal, Ungated),
737 ("no_implicit_prelude", Normal, Ungated),
738 ("reexport_test_harness_main", Normal, Ungated),
739 ("link_args", Normal, Gated(Stability::Unstable,
741 "the `link_args` attribute is experimental and not \
742 portable across platforms, it is recommended to \
743 use `#[link(name = \"foo\")] instead",
744 cfg_fn!(link_args))),
745 ("macro_escape", Normal, Ungated),
748 ("structural_match", Whitelisted, Gated(Stability::Unstable,
750 "the semantics of constant patterns is \
752 cfg_fn!(structural_match))),
755 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
757 "non exhaustive is an experimental feature",
758 cfg_fn!(non_exhaustive))),
760 ("plugin", CrateLevel, Gated(Stability::Unstable,
762 "compiler plugins are experimental \
766 ("no_std", CrateLevel, Ungated),
767 ("no_core", CrateLevel, Gated(Stability::Unstable,
769 "no_core is experimental",
771 ("lang", Normal, Gated(Stability::Unstable,
773 "language items are subject to change",
774 cfg_fn!(lang_items))),
775 ("linkage", Whitelisted, Gated(Stability::Unstable,
777 "the `linkage` attribute is experimental \
778 and not portable across platforms",
780 ("thread_local", Whitelisted, Gated(Stability::Unstable,
782 "`#[thread_local]` is an experimental feature, and does \
783 not currently handle destructors.",
784 cfg_fn!(thread_local))),
786 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
788 "the `#[rustc_on_unimplemented]` attribute \
789 is an experimental feature",
790 cfg_fn!(on_unimplemented))),
791 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
792 "rustc_const_unstable",
793 "the `#[rustc_const_unstable]` attribute \
794 is an internal feature",
795 cfg_fn!(rustc_const_unstable))),
796 ("global_allocator", Normal, Ungated),
797 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
798 "allocator_internals",
799 "the `#[default_lib_allocator]` \
800 attribute is an experimental feature",
801 cfg_fn!(allocator_internals))),
802 ("needs_allocator", Normal, Gated(Stability::Unstable,
803 "allocator_internals",
804 "the `#[needs_allocator]` \
805 attribute is an experimental \
807 cfg_fn!(allocator_internals))),
808 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
810 "the `#[panic_runtime]` attribute is \
811 an experimental feature",
812 cfg_fn!(panic_runtime))),
813 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
814 "needs_panic_runtime",
815 "the `#[needs_panic_runtime]` \
816 attribute is an experimental \
818 cfg_fn!(needs_panic_runtime))),
819 ("rustc_outlives", Normal, Gated(Stability::Unstable,
821 "the `#[rustc_outlives]` attribute \
822 is just used for rustc unit tests \
823 and will never be stable",
824 cfg_fn!(rustc_attrs))),
825 ("rustc_variance", Normal, Gated(Stability::Unstable,
827 "the `#[rustc_variance]` attribute \
828 is just used for rustc unit tests \
829 and will never be stable",
830 cfg_fn!(rustc_attrs))),
831 ("rustc_regions", Normal, Gated(Stability::Unstable,
833 "the `#[rustc_regions]` attribute \
834 is just used for rustc unit tests \
835 and will never be stable",
836 cfg_fn!(rustc_attrs))),
837 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
839 "the `#[rustc_error]` attribute \
840 is just used for rustc unit tests \
841 and will never be stable",
842 cfg_fn!(rustc_attrs))),
843 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
845 "the `#[rustc_if_this_changed]` attribute \
846 is just used for rustc unit tests \
847 and will never be stable",
848 cfg_fn!(rustc_attrs))),
849 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
851 "the `#[rustc_if_this_changed]` attribute \
852 is just used for rustc unit tests \
853 and will never be stable",
854 cfg_fn!(rustc_attrs))),
855 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
857 "the `#[rustc_dirty]` attribute \
858 is just used for rustc unit tests \
859 and will never be stable",
860 cfg_fn!(rustc_attrs))),
861 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
863 "the `#[rustc_clean]` attribute \
864 is just used for rustc unit tests \
865 and will never be stable",
866 cfg_fn!(rustc_attrs))),
867 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
870 is just used for rustc unit tests \
871 and will never be stable",
872 cfg_fn!(rustc_attrs))),
873 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
876 is just used for rustc unit tests \
877 and will never be stable",
878 cfg_fn!(rustc_attrs))),
879 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
882 is just used for rustc unit tests \
883 and will never be stable",
884 cfg_fn!(rustc_attrs))),
885 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
887 "internal rustc attributes will never be stable",
888 cfg_fn!(rustc_attrs))),
889 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
891 "internal rustc attributes will never be stable",
892 cfg_fn!(rustc_attrs))),
893 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
895 "the `#[rustc_mir]` attribute \
896 is just used for rustc unit tests \
897 and will never be stable",
898 cfg_fn!(rustc_attrs))),
899 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
901 "the `#[rustc_inherit_overflow_checks]` \
902 attribute is just used to control \
903 overflow checking behavior of several \
904 libcore functions that are inlined \
905 across crates and will never be stable",
906 cfg_fn!(rustc_attrs))),
908 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
910 "the `#[rustc_dump_program_clauses]` \
911 attribute is just used for rustc unit \
912 tests and will never be stable",
913 cfg_fn!(rustc_attrs))),
916 ("nll", Whitelisted, Gated(Stability::Unstable,
918 "Non lexical lifetimes",
920 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
922 "the `#[compiler_builtins]` attribute is used to \
923 identify the `compiler_builtins` crate which \
924 contains compiler-rt intrinsics and will never be \
926 cfg_fn!(compiler_builtins))),
927 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
929 "the `#[sanitizer_runtime]` attribute is used to \
930 identify crates that contain the runtime of a \
931 sanitizer and will never be stable",
932 cfg_fn!(sanitizer_runtime))),
933 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
935 "the `#[profiler_runtime]` attribute is used to \
936 identify the `profiler_builtins` crate which \
937 contains the profiler runtime and will never be \
939 cfg_fn!(profiler_runtime))),
941 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
942 "allow_internal_unstable",
943 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
944 cfg_fn!(allow_internal_unstable))),
946 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
947 "allow_internal_unsafe",
948 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
949 cfg_fn!(allow_internal_unsafe))),
951 ("fundamental", Whitelisted, Gated(Stability::Unstable,
953 "the `#[fundamental]` attribute \
954 is an experimental feature",
955 cfg_fn!(fundamental))),
957 ("proc_macro_derive", Normal, Ungated),
959 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
961 "internal implementation detail",
962 cfg_fn!(rustc_attrs))),
964 // FIXME: #14408 whitelist docs since rustdoc looks at them
965 ("doc", Whitelisted, Ungated),
967 // FIXME: #14406 these are processed in codegen, which happens after the
969 ("cold", Whitelisted, Ungated),
970 ("naked", Whitelisted, Gated(Stability::Unstable,
972 "the `#[naked]` attribute \
973 is an experimental feature",
974 cfg_fn!(naked_functions))),
975 ("target_feature", Whitelisted, Ungated),
976 ("export_name", Whitelisted, Ungated),
977 ("inline", Whitelisted, Ungated),
978 ("link", Whitelisted, Ungated),
979 ("link_name", Whitelisted, Ungated),
980 ("link_section", Whitelisted, Ungated),
981 ("no_builtins", Whitelisted, Ungated),
982 ("no_mangle", Whitelisted, Ungated),
983 ("no_debug", Whitelisted, Gated(
984 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
986 "the `#[no_debug]` attribute was an experimental feature that has been \
987 deprecated due to lack of demand",
989 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
990 "omit_gdb_pretty_printer_section",
991 "the `#[omit_gdb_pretty_printer_section]` \
992 attribute is just used for the Rust test \
994 cfg_fn!(omit_gdb_pretty_printer_section))),
995 ("unsafe_destructor_blind_to_params",
997 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761"),
998 "dropck_parametricity",
999 "unsafe_destructor_blind_to_params has been replaced by \
1000 may_dangle and will be removed in the future",
1001 cfg_fn!(dropck_parametricity))),
1004 Gated(Stability::Unstable,
1006 "may_dangle has unstable semantics and may be removed in the future",
1007 cfg_fn!(dropck_eyepatch))),
1008 ("unwind", Whitelisted, Gated(Stability::Unstable,
1009 "unwind_attributes",
1010 "#[unwind] is experimental",
1011 cfg_fn!(unwind_attributes))),
1012 ("used", Whitelisted, Gated(
1013 Stability::Unstable, "used",
1014 "the `#[used]` attribute is an experimental feature",
1018 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1020 "`#[prelude_import]` is for use by rustc only",
1021 cfg_fn!(prelude_import))),
1023 // FIXME: #14407 these are only looked at on-demand so we can't
1024 // guarantee they'll have already been checked
1025 ("rustc_deprecated", Whitelisted, Ungated),
1026 ("must_use", Whitelisted, Ungated),
1027 ("stable", Whitelisted, Ungated),
1028 ("unstable", Whitelisted, Ungated),
1029 ("deprecated", Normal, Ungated),
1031 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1033 "unboxed_closures are still evolving",
1034 cfg_fn!(unboxed_closures))),
1036 ("windows_subsystem", Whitelisted, Ungated),
1038 ("proc_macro_attribute", Normal, Ungated),
1039 ("proc_macro", Normal, Ungated),
1041 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
1042 "rustc_derive_registrar",
1043 "used internally by rustc",
1044 cfg_fn!(rustc_attrs))),
1046 ("allow_fail", Normal, Gated(Stability::Unstable,
1048 "allow_fail attribute is currently unstable",
1049 cfg_fn!(allow_fail))),
1051 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1053 "this is an internal attribute that will \
1055 cfg_fn!(rustc_attrs))),
1057 // whitelists "identity-like" conversion methods to suggest on type mismatch
1058 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1060 "this is an internal attribute that will \
1062 cfg_fn!(rustc_attrs))),
1064 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1066 "never will be stable",
1067 cfg_fn!(rustc_attrs))),
1070 ("infer_outlives_requirements", Normal, Gated(Stability::Unstable,
1071 "infer_outlives_requirements",
1072 "infer outlives requirements is an experimental feature",
1073 cfg_fn!(infer_outlives_requirements))),
1076 ("infer_static_outlives_requirements", Normal, Gated(Stability::Unstable,
1077 "infer_static_outlives_requirements",
1078 "infer 'static lifetime requirements",
1079 cfg_fn!(infer_static_outlives_requirements))),
1082 ("panic_implementation", Normal, Gated(Stability::Unstable,
1083 "panic_implementation",
1084 "#[panic_implementation] is an unstable feature",
1085 cfg_fn!(panic_implementation))),
1087 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1088 "alloc_error_handler",
1089 "#[alloc_error_handler] is an unstable feature",
1090 cfg_fn!(alloc_error_handler))),
1092 // Crate level attributes
1093 ("crate_name", CrateLevel, Ungated),
1094 ("crate_type", CrateLevel, Ungated),
1095 ("crate_id", CrateLevel, Ungated),
1096 ("feature", CrateLevel, Ungated),
1097 ("no_start", CrateLevel, Ungated),
1098 ("no_main", CrateLevel, Ungated),
1099 ("no_builtins", CrateLevel, Ungated),
1100 ("recursion_limit", CrateLevel, Ungated),
1101 ("type_length_limit", CrateLevel, Ungated),
1104 // cfg(...)'s that are feature gated
1105 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1106 // (name in cfg, feature, function to check if the feature is enabled)
1107 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1108 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1109 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1113 pub struct GatedCfg {
1119 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1120 let name = cfg.name().as_str();
1122 .position(|info| info.0 == name)
1131 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1132 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1133 if !has_feature(features) && !self.span.allows_unstable() {
1134 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1135 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1140 struct Context<'a> {
1141 features: &'a Features,
1142 parse_sess: &'a ParseSess,
1143 plugin_attributes: &'a [(String, AttributeType)],
1146 macro_rules! gate_feature_fn {
1147 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1148 let (cx, has_feature, span,
1149 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1150 let has_feature: bool = has_feature(&$cx.features);
1151 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1152 if !has_feature && !span.allows_unstable() {
1153 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1159 macro_rules! gate_feature {
1160 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1161 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1162 stringify!($feature), $explain, GateStrength::Hard)
1164 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1165 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1166 stringify!($feature), $explain, $level)
1170 impl<'a> Context<'a> {
1171 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1172 debug!("check_attribute(attr = {:?})", attr);
1173 let name = attr.name().as_str();
1174 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1176 if let Gated(_, name, desc, ref has_feature) = *gateage {
1177 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1178 } else if name == "doc" {
1179 if let Some(content) = attr.meta_item_list() {
1180 if content.iter().any(|c| c.check_name("include")) {
1181 gate_feature!(self, external_doc, attr.span,
1182 "#[doc(include = \"...\")] is experimental"
1187 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1191 for &(ref n, ref ty) in self.plugin_attributes {
1192 if attr.path == &**n {
1193 // Plugins can't gate attributes, so we don't check for it
1194 // unlike the code above; we only use this loop to
1195 // short-circuit to avoid the checks below
1196 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1200 if name.starts_with("rustc_") {
1201 gate_feature!(self, rustc_attrs, attr.span,
1202 "unless otherwise specified, attributes \
1203 with the prefix `rustc_` \
1204 are reserved for internal compiler diagnostics");
1205 } else if name.starts_with("derive_") {
1206 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1207 } else if !attr::is_known(attr) {
1208 // Only run the custom attribute lint during regular
1209 // feature gate checking. Macro gating runs
1210 // before the plugin attributes are registered
1211 // so we skip this then
1213 let msg = format!("The attribute `{}` is currently unknown to the compiler and \
1214 may have meaning added to it in the future", attr.path);
1215 gate_feature!(self, custom_attribute, attr.span, &msg);
1221 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1222 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1223 cx.check_attribute(attr, true);
1226 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1227 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1229 // FIXME (#28244): enforce that active features have issue numbers
1230 // assert!(issue.is_some())
1233 // search in Accepted, Removed, or Stable Removed features
1234 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1235 .find(|t| t.0 == feature);
1237 Some(&(_, _, issue, _)) => issue,
1238 None => panic!("Feature `{}` is not declared anywhere", feature),
1243 pub enum GateIssue {
1245 Library(Option<u32>)
1248 #[derive(Debug, Copy, Clone, PartialEq)]
1249 pub enum GateStrength {
1250 /// A hard error. (Most feature gates should use this.)
1252 /// Only a warning. (Use this only as backwards-compatibility demands.)
1256 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1258 feature_err(sess, feature, span, issue, explain).emit();
1261 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1262 explain: &str) -> DiagnosticBuilder<'a> {
1263 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1266 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1267 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1268 let diag = &sess.span_diagnostic;
1270 let issue = match issue {
1271 GateIssue::Language => find_lang_feature_issue(feature),
1272 GateIssue::Library(lib) => lib,
1275 let explanation = match issue {
1276 None | Some(0) => explain.to_owned(),
1277 Some(n) => format!("{} (see issue #{})", explain, n)
1280 let mut err = match level {
1281 GateStrength::Hard => {
1282 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1284 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1287 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1288 if sess.unstable_features.is_nightly_build() {
1289 err.help(&format!("add #![feature({})] to the \
1290 crate attributes to enable",
1294 // If we're on stable and only emitting a "soft" warning, add a note to
1295 // clarify that the feature isn't "on" (rather than being on but
1297 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1298 err.help("a nightly build of the compiler is required to enable this feature");
1305 const EXPLAIN_BOX_SYNTAX: &'static str =
1306 "box expression syntax is experimental; you can call `Box::new` instead.";
1308 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1309 "attributes on expressions are experimental.";
1311 pub const EXPLAIN_ASM: &'static str =
1312 "inline assembly is not stable enough for use and is subject to change";
1314 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1315 "`global_asm!` is not stable enough for use and is subject to change";
1317 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1318 "`log_syntax!` is not stable enough for use and is subject to change";
1320 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1321 "`concat_idents` is not stable enough for use and is subject to change";
1323 pub const EXPLAIN_FORMAT_ARGS_NL: &'static str =
1324 "`format_args_nl` is only for internal language use and is subject to change";
1326 pub const EXPLAIN_TRACE_MACROS: &'static str =
1327 "`trace_macros` is not stable enough for use and is subject to change";
1328 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1329 "allow_internal_unstable side-steps feature gating and stability checks";
1330 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1331 "allow_internal_unsafe side-steps the unsafe_code lint";
1333 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1334 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1336 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1337 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1338 Prefer using procedural macro custom derive.";
1340 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1341 "attributes of the form `#[derive_*]` are reserved for the compiler";
1343 pub const EXPLAIN_VIS_MATCHER: &'static str =
1344 ":vis fragment specifier is experimental and subject to change";
1346 pub const EXPLAIN_LITERAL_MATCHER: &'static str =
1347 ":literal fragment specifier is experimental and subject to change";
1349 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1350 "unsized tuple coercion is not stable enough for use and is subject to change";
1352 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
1353 "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1355 pub const EXPLAIN_MACROS_IN_EXTERN: &'static str =
1356 "macro invocations in `extern {}` blocks are experimental.";
1358 // mention proc-macros when enabled
1359 pub const EXPLAIN_PROC_MACROS_IN_EXTERN: &'static str =
1360 "macro and proc-macro invocations in `extern {}` blocks are experimental.";
1362 struct PostExpansionVisitor<'a> {
1363 context: &'a Context<'a>,
1366 macro_rules! gate_feature_post {
1367 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1368 let (cx, span) = ($cx, $span);
1369 if !span.allows_unstable() {
1370 gate_feature!(cx.context, $feature, span, $explain)
1373 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1374 let (cx, span) = ($cx, $span);
1375 if !span.allows_unstable() {
1376 gate_feature!(cx.context, $feature, span, $explain, $level)
1381 impl<'a> PostExpansionVisitor<'a> {
1382 fn check_abi(&self, abi: Abi, span: Span) {
1384 Abi::RustIntrinsic => {
1385 gate_feature_post!(&self, intrinsics, span,
1386 "intrinsics are subject to change");
1388 Abi::PlatformIntrinsic => {
1389 gate_feature_post!(&self, platform_intrinsics, span,
1390 "platform intrinsics are experimental and possibly buggy");
1392 Abi::Vectorcall => {
1393 gate_feature_post!(&self, abi_vectorcall, span,
1394 "vectorcall is experimental and subject to change");
1397 gate_feature_post!(&self, abi_thiscall, span,
1398 "thiscall is experimental and subject to change");
1401 gate_feature_post!(&self, unboxed_closures, span,
1402 "rust-call ABI is subject to change");
1405 gate_feature_post!(&self, abi_ptx, span,
1406 "PTX ABIs are experimental and subject to change");
1408 Abi::Unadjusted => {
1409 gate_feature_post!(&self, abi_unadjusted, span,
1410 "unadjusted ABI is an implementation detail and perma-unstable");
1412 Abi::Msp430Interrupt => {
1413 gate_feature_post!(&self, abi_msp430_interrupt, span,
1414 "msp430-interrupt ABI is experimental and subject to change");
1416 Abi::X86Interrupt => {
1417 gate_feature_post!(&self, abi_x86_interrupt, span,
1418 "x86-interrupt ABI is experimental and subject to change");
1420 Abi::AmdGpuKernel => {
1421 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1422 "amdgpu-kernel ABI is experimental and subject to change");
1438 fn contains_novel_literal(item: &ast::MetaItem) -> bool {
1439 use ast::MetaItemKind::*;
1440 use ast::NestedMetaItemKind::*;
1444 NameValue(ref lit) => !lit.node.is_str(),
1445 List(ref list) => list.iter().any(|li| {
1447 MetaItem(ref mi) => contains_novel_literal(mi),
1454 impl<'a> PostExpansionVisitor<'a> {
1455 fn whole_crate_feature_gates(&mut self, _krate: &ast::Crate) {
1456 for &(ident, span) in &*self.context.parse_sess.non_modrs_mods.borrow() {
1457 if !span.allows_unstable() {
1458 let cx = &self.context;
1459 let level = GateStrength::Hard;
1460 let has_feature = cx.features.non_modrs_mods;
1461 let name = "non_modrs_mods";
1462 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}",
1463 name, span, has_feature);
1465 if !has_feature && !span.allows_unstable() {
1466 leveled_feature_err(
1467 cx.parse_sess, name, span, GateIssue::Language,
1468 "mod statements in non-mod.rs files are unstable", level
1470 .help(&format!("on stable builds, rename this file to {}{}mod.rs",
1471 ident, path::MAIN_SEPARATOR))
1479 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1480 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1481 if !attr.span.allows_unstable() {
1482 // check for gated attributes
1483 self.context.check_attribute(attr, false);
1486 if attr.check_name("doc") {
1487 if let Some(content) = attr.meta_item_list() {
1488 if content.len() == 1 && content[0].check_name("cfg") {
1489 gate_feature_post!(&self, doc_cfg, attr.span,
1490 "#[doc(cfg(...))] is experimental"
1492 } else if content.iter().any(|c| c.check_name("masked")) {
1493 gate_feature_post!(&self, doc_masked, attr.span,
1494 "#[doc(masked)] is experimental"
1496 } else if content.iter().any(|c| c.check_name("spotlight")) {
1497 gate_feature_post!(&self, doc_spotlight, attr.span,
1498 "#[doc(spotlight)] is experimental"
1500 } else if content.iter().any(|c| c.check_name("alias")) {
1501 gate_feature_post!(&self, doc_alias, attr.span,
1502 "#[doc(alias = \"...\")] is experimental"
1504 } else if content.iter().any(|c| c.check_name("keyword")) {
1505 gate_feature_post!(&self, doc_keyword, attr.span,
1506 "#[doc(keyword = \"...\")] is experimental"
1512 // allow attr_literals in #[repr(align(x))] and #[repr(packed(n))]
1513 let mut allow_attr_literal = false;
1514 if attr.path == "repr" {
1515 if let Some(content) = attr.meta_item_list() {
1516 allow_attr_literal = content.iter().any(
1517 |c| c.check_name("align") || c.check_name("packed"));
1521 if self.context.features.use_extern_macros() && attr::is_known(attr) {
1525 if !allow_attr_literal {
1526 let meta = panictry!(attr.parse_meta(self.context.parse_sess));
1527 if contains_novel_literal(&meta) {
1528 gate_feature_post!(&self, attr_literals, attr.span,
1529 "non-string literals in attributes, or string \
1530 literals in top-level positions, are experimental");
1535 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1536 if !name.as_str().is_ascii() {
1537 gate_feature_post!(&self,
1539 self.context.parse_sess.codemap().def_span(sp),
1540 "non-ascii idents are not fully supported.");
1544 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1545 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1546 if ident.name == "_" {
1547 gate_feature_post!(&self, underscore_imports, use_tree.span,
1548 "renaming imports with `_` is unstable");
1552 visit::walk_use_tree(self, use_tree, id);
1555 fn visit_item(&mut self, i: &'a ast::Item) {
1557 ast::ItemKind::ExternCrate(_) => {
1558 if i.ident.name == "_" {
1559 gate_feature_post!(&self, underscore_imports, i.span,
1560 "renaming extern crates with `_` is unstable");
1564 ast::ItemKind::ForeignMod(ref foreign_module) => {
1565 self.check_abi(foreign_module.abi, i.span);
1568 ast::ItemKind::Fn(..) => {
1569 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1570 gate_feature_post!(&self, plugin_registrar, i.span,
1571 "compiler plugins are experimental and possibly buggy");
1573 if attr::contains_name(&i.attrs[..], "start") {
1574 gate_feature_post!(&self, start, i.span,
1575 "a #[start] function is an experimental \
1576 feature whose signature may change \
1579 if attr::contains_name(&i.attrs[..], "main") {
1580 gate_feature_post!(&self, main, i.span,
1581 "declaration of a nonstandard #[main] \
1582 function may change over time, for now \
1583 a top-level `fn main()` is required");
1587 ast::ItemKind::Struct(..) => {
1588 if let Some(attr) = attr::find_by_name(&i.attrs[..], "repr") {
1589 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1590 if item.check_name("simd") {
1591 gate_feature_post!(&self, repr_simd, attr.span,
1592 "SIMD types are experimental and possibly buggy");
1594 if let Some((name, _)) = item.name_value_literal() {
1595 if name == "packed" {
1596 gate_feature_post!(&self, repr_packed, attr.span,
1597 "the `#[repr(packed(n))]` attribute \
1605 ast::ItemKind::TraitAlias(..) => {
1606 gate_feature_post!(&self, trait_alias,
1608 "trait aliases are not yet fully implemented");
1611 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1612 if polarity == ast::ImplPolarity::Negative {
1613 gate_feature_post!(&self, optin_builtin_traits,
1615 "negative trait bounds are not yet fully implemented; \
1616 use marker types for now");
1619 if let ast::Defaultness::Default = defaultness {
1620 gate_feature_post!(&self, specialization,
1622 "specialization is unstable");
1626 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1627 gate_feature_post!(&self, optin_builtin_traits,
1629 "auto traits are experimental and possibly buggy");
1632 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1633 let msg = "`macro` is experimental";
1634 gate_feature_post!(&self, decl_macro, i.span, msg);
1637 ast::ItemKind::Existential(..) => {
1642 "existential types are unstable"
1649 visit::walk_item(self, i);
1652 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1654 ast::ForeignItemKind::Fn(..) |
1655 ast::ForeignItemKind::Static(..) => {
1656 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1657 let links_to_llvm = match link_name {
1658 Some(val) => val.as_str().starts_with("llvm."),
1662 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1663 "linking to LLVM intrinsics is experimental");
1666 ast::ForeignItemKind::Ty => {
1667 gate_feature_post!(&self, extern_types, i.span,
1668 "extern types are experimental");
1670 ast::ForeignItemKind::Macro(..) => {}
1673 visit::walk_foreign_item(self, i)
1676 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1678 ast::TyKind::BareFn(ref bare_fn_ty) => {
1679 self.check_abi(bare_fn_ty.abi, ty.span);
1681 ast::TyKind::Never => {
1682 gate_feature_post!(&self, never_type, ty.span,
1683 "The `!` type is experimental");
1687 visit::walk_ty(self, ty)
1690 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1691 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1692 if let ast::TyKind::Never = output_ty.node {
1695 self.visit_ty(output_ty)
1700 fn visit_expr(&mut self, e: &'a ast::Expr) {
1702 ast::ExprKind::Box(_) => {
1703 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1705 ast::ExprKind::Type(..) => {
1706 gate_feature_post!(&self, type_ascription, e.span,
1707 "type ascription is experimental");
1709 ast::ExprKind::ObsoleteInPlace(..) => {
1710 // these get a hard error in ast-validation
1712 ast::ExprKind::Yield(..) => {
1713 gate_feature_post!(&self, generators,
1715 "yield syntax is experimental");
1717 ast::ExprKind::Catch(_) => {
1718 gate_feature_post!(&self, catch_expr, e.span, "`catch` expression is experimental");
1720 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1722 gate_feature_post!(&self, if_while_or_patterns, e.span,
1723 "multiple patterns in `if let` and `while let` are unstable");
1726 ast::ExprKind::Block(_, opt_label) => {
1727 if let Some(label) = opt_label {
1728 gate_feature_post!(&self, label_break_value, label.ident.span,
1729 "labels on blocks are unstable");
1732 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1733 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1735 ast::ExprKind::Async(..) => {
1736 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1740 visit::walk_expr(self, e);
1743 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1744 visit::walk_arm(self, arm)
1747 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1748 match pattern.node {
1749 PatKind::Slice(_, Some(ref subslice), _) => {
1750 gate_feature_post!(&self, slice_patterns,
1752 "syntax for subslices in slice patterns is not yet stabilized");
1754 PatKind::Box(..) => {
1755 gate_feature_post!(&self, box_patterns,
1757 "box pattern syntax is experimental");
1759 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1760 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1761 "exclusive range pattern syntax is experimental");
1763 PatKind::Paren(..) => {
1764 gate_feature_post!(&self, pattern_parentheses, pattern.span,
1765 "parentheses in patterns are unstable");
1769 visit::walk_pat(self, pattern)
1772 fn visit_fn(&mut self,
1773 fn_kind: FnKind<'a>,
1774 fn_decl: &'a ast::FnDecl,
1778 FnKind::ItemFn(_, header, _, _) => {
1779 // check for const fn and async fn declarations
1780 if header.asyncness.is_async() {
1781 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1783 if header.constness.node == ast::Constness::Const {
1784 gate_feature_post!(&self, const_fn, span, "const fn is unstable");
1786 // stability of const fn methods are covered in
1787 // visit_trait_item and visit_impl_item below; this is
1788 // because default methods don't pass through this
1791 self.check_abi(header.abi, span);
1793 FnKind::Method(_, sig, _, _) => {
1794 self.check_abi(sig.header.abi, span);
1798 visit::walk_fn(self, fn_kind, fn_decl, span);
1801 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1803 ast::TraitItemKind::Method(ref sig, ref block) => {
1804 if block.is_none() {
1805 self.check_abi(sig.header.abi, ti.span);
1807 if sig.header.constness.node == ast::Constness::Const {
1808 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1811 ast::TraitItemKind::Type(_, ref default) => {
1812 // We use three if statements instead of something like match guards so that all
1813 // of these errors can be emitted if all cases apply.
1814 if default.is_some() {
1815 gate_feature_post!(&self, associated_type_defaults, ti.span,
1816 "associated type defaults are unstable");
1818 if !ti.generics.params.is_empty() {
1819 gate_feature_post!(&self, generic_associated_types, ti.span,
1820 "generic associated types are unstable");
1822 if !ti.generics.where_clause.predicates.is_empty() {
1823 gate_feature_post!(&self, generic_associated_types, ti.span,
1824 "where clauses on associated types are unstable");
1829 visit::walk_trait_item(self, ti);
1832 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1833 if ii.defaultness == ast::Defaultness::Default {
1834 gate_feature_post!(&self, specialization,
1836 "specialization is unstable");
1840 ast::ImplItemKind::Method(ref sig, _) => {
1841 if sig.header.constness.node == ast::Constness::Const {
1842 gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable");
1845 ast::ImplItemKind::Existential(..) => {
1850 "existential types are unstable"
1854 ast::ImplItemKind::Type(_) if !ii.generics.params.is_empty() => {
1855 gate_feature_post!(&self, generic_associated_types, ii.span,
1856 "generic associated types are unstable");
1860 visit::walk_impl_item(self, ii);
1863 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1864 for segment in &path.segments {
1865 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1866 // For such macros identifiers must have empty context, because this context is
1867 // used during name resolution and produced names must be unhygienic for compatibility.
1868 // On the other hand, we need the actual non-empty context for feature gate checking
1869 // because it's hygienic even for legacy macros. As previously stated, such context
1870 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1871 // there while keeping location info from the ident span.
1872 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1873 if segment.ident.name == keywords::Crate.name() {
1874 gate_feature_post!(&self, crate_in_paths, span,
1875 "`crate` in paths is experimental");
1876 } else if segment.ident.name == keywords::Extern.name() {
1877 gate_feature_post!(&self, extern_in_paths, span,
1878 "`extern` in paths is experimental");
1882 visit::walk_path(self, path);
1885 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1886 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1887 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1888 "`crate` visibility modifier is experimental");
1890 visit::walk_vis(self, vis);
1894 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1895 crate_edition: Edition) -> Features {
1896 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1897 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1898 if let Some(reason) = reason {
1899 err.span_note(span, reason);
1904 let mut features = Features::new();
1906 let mut feature_checker = FeatureChecker::default();
1908 let mut edition_enabled_features = FxHashMap();
1910 for &(name, .., f_edition, set) in ACTIVE_FEATURES.iter() {
1911 if let Some(f_edition) = f_edition {
1912 if f_edition <= crate_edition {
1913 set(&mut features, DUMMY_SP);
1914 edition_enabled_features.insert(Symbol::intern(name), crate_edition);
1919 for attr in krate_attrs {
1920 if !attr.check_name("feature") {
1924 let list = match attr.meta_item_list() {
1927 span_err!(span_handler, attr.span, E0555,
1928 "malformed feature attribute, expected #![feature(...)]");
1934 let name = if let Some(word) = mi.word() {
1937 span_err!(span_handler, mi.span, E0556,
1938 "malformed feature, expected just one word");
1942 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1943 if *edition <= crate_edition {
1947 for &(name, .., f_edition, set) in ACTIVE_FEATURES.iter() {
1948 if let Some(f_edition) = f_edition {
1949 if f_edition <= *edition {
1950 // FIXME(Manishearth) there is currently no way to set
1951 // lib features by edition
1952 set(&mut features, DUMMY_SP);
1953 edition_enabled_features.insert(Symbol::intern(name), *edition);
1961 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
1962 if let Some(edition) = edition_enabled_features.get(&name) {
1967 "the feature `{}` is included in the Rust {} edition",
1972 set(&mut features, mi.span);
1973 feature_checker.collect(&features, mi.span);
1974 features.declared_lang_features.push((name, mi.span, None));
1979 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
1980 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
1981 if let Some((.., reason)) = removed.or(stable_removed) {
1982 feature_removed(span_handler, mi.span, *reason);
1986 if let Some((_, since, ..)) = ACCEPTED_FEATURES.iter().find(|f| name == f.0) {
1987 let since = Some(Symbol::intern(since));
1988 features.declared_lang_features.push((name, mi.span, since));
1992 features.declared_lib_features.push((name, mi.span));
1996 feature_checker.check(span_handler);
2001 /// A collector for mutually exclusive and interdependent features and their flag spans.
2003 struct FeatureChecker {
2004 use_extern_macros: Option<Span>,
2005 custom_attribute: Option<Span>,
2008 impl FeatureChecker {
2009 // If this method turns out to be a hotspot due to branching,
2010 // the branching can be eliminated by modifying `set!()` to set these spans
2011 // only for the features that need to be checked for mutual exclusion.
2012 fn collect(&mut self, features: &Features, span: Span) {
2013 if features.use_extern_macros() {
2014 // If self.use_extern_macros is None, set to Some(span)
2015 self.use_extern_macros = self.use_extern_macros.or(Some(span));
2018 if features.custom_attribute {
2019 self.custom_attribute = self.custom_attribute.or(Some(span));
2023 fn check(self, handler: &Handler) {
2024 if let (Some(pm_span), Some(ca_span)) = (self.use_extern_macros, self.custom_attribute) {
2025 handler.struct_span_err(pm_span, "Cannot use `#![feature(use_extern_macros)]` and \
2026 `#![feature(custom_attribute)] at the same time")
2027 .span_note(ca_span, "`#![feature(custom_attribute)]` declared here")
2035 pub fn check_crate(krate: &ast::Crate,
2037 features: &Features,
2038 plugin_attributes: &[(String, AttributeType)],
2039 unstable: UnstableFeatures) {
2040 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2047 if !features.raw_identifiers {
2048 for &span in sess.raw_identifier_spans.borrow().iter() {
2049 if !span.allows_unstable() {
2050 gate_feature!(&ctx, raw_identifiers, span,
2051 "raw identifiers are experimental and subject to change"
2057 let visitor = &mut PostExpansionVisitor { context: &ctx };
2058 visitor.whole_crate_feature_gates(krate);
2059 visit::walk_crate(visitor, krate);
2062 #[derive(Clone, Copy, Hash)]
2063 pub enum UnstableFeatures {
2064 /// Hard errors for unstable features are active, as on
2065 /// beta/stable channels.
2067 /// Allow features to be activated, as on nightly.
2069 /// Errors are bypassed for bootstrapping. This is required any time
2070 /// during the build that feature-related lints are set to warn or above
2071 /// because the build turns on warnings-as-errors and uses lots of unstable
2072 /// features. As a result, this is always required for building Rust itself.
2076 impl UnstableFeatures {
2077 pub fn from_environment() -> UnstableFeatures {
2078 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2079 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2080 // Whether we should enable unstable features for bootstrapping
2081 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2082 match (disable_unstable_features, bootstrap) {
2083 (_, true) => UnstableFeatures::Cheat,
2084 (true, _) => UnstableFeatures::Disallow,
2085 (false, _) => UnstableFeatures::Allow
2089 pub fn is_nightly_build(&self) -> bool {
2091 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2097 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2098 unstable: UnstableFeatures) {
2099 let allow_features = match unstable {
2100 UnstableFeatures::Allow => true,
2101 UnstableFeatures::Disallow => false,
2102 UnstableFeatures::Cheat => true
2104 if !allow_features {
2105 for attr in &krate.attrs {
2106 if attr.check_name("feature") {
2107 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2108 span_err!(span_handler, attr.span, E0554,
2109 "#![feature] may not be used on the {} release channel",