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_target::spec::abi::Abi;
29 use ast::{self, NodeId, PatKind, RangeEnd};
32 use edition::{ALL_EDITIONS, Edition};
33 use syntax_pos::{Span, DUMMY_SP};
34 use errors::{DiagnosticBuilder, Handler, FatalError};
35 use visit::{self, FnKind, Visitor};
37 use symbol::{keywords, Symbol};
43 fn f(features: &mut Features, _: Span) {
44 features.$field = true;
46 f as fn(&mut Features, Span)
50 macro_rules! declare_features {
51 ($((active, $feature: ident, $ver: expr, $issue: expr, $edition: expr),)+) => {
52 /// Represents active features that are currently being implemented or
53 /// currently being considered for addition/removal.
54 const ACTIVE_FEATURES:
55 &'static [(&'static str, &'static str, Option<u32>,
56 Option<Edition>, fn(&mut Features, Span))] =
57 &[$((stringify!($feature), $ver, $issue, $edition, set!($feature))),+];
59 /// A set of features to be used by later passes.
62 /// `#![feature]` attrs for stable language features, for error reporting
63 pub declared_stable_lang_features: Vec<(Symbol, Span)>,
64 /// `#![feature]` attrs for non-language (library) features
65 pub declared_lib_features: Vec<(Symbol, Span)>,
66 $(pub $feature: bool),+
70 pub fn new() -> Features {
72 declared_stable_lang_features: Vec::new(),
73 declared_lib_features: Vec::new(),
78 pub fn walk_feature_fields<F>(&self, mut f: F)
79 where F: FnMut(&str, bool)
81 $(f(stringify!($feature), self.$feature);)+
86 ($((removed, $feature: ident, $ver: expr, $issue: expr, None, $reason: expr),)+) => {
87 /// Represents unstable features which have since been removed (it was once Active)
88 const REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
89 $((stringify!($feature), $ver, $issue, $reason)),+
93 ($((stable_removed, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
94 /// Represents stable features which have since been removed (it was once Accepted)
95 const STABLE_REMOVED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
96 $((stringify!($feature), $ver, $issue, None)),+
100 ($((accepted, $feature: ident, $ver: expr, $issue: expr, None),)+) => {
101 /// Those language feature has since been Accepted (it was once Active)
102 const ACCEPTED_FEATURES: &[(&str, &str, Option<u32>, Option<&str>)] = &[
103 $((stringify!($feature), $ver, $issue, None)),+
108 // If you change this, please modify src/doc/unstable-book as well.
110 // Don't ever remove anything from this list; set them to 'Removed'.
112 // The version numbers here correspond to the version in which the current status
113 // was set. This is most important for knowing when a particular feature became
116 // NB: tools/tidy/src/features.rs parses this information directly out of the
117 // source, so take care when modifying it.
120 (active, asm, "1.0.0", Some(29722), None),
121 (active, concat_idents, "1.0.0", Some(29599), None),
122 (active, link_args, "1.0.0", Some(29596), None),
123 (active, log_syntax, "1.0.0", Some(29598), None),
124 (active, non_ascii_idents, "1.0.0", Some(28979), None),
125 (active, plugin_registrar, "1.0.0", Some(29597), None),
126 (active, thread_local, "1.0.0", Some(29594), None),
127 (active, trace_macros, "1.0.0", Some(29598), None),
129 // rustc internal, for now:
130 (active, intrinsics, "1.0.0", None, None),
131 (active, lang_items, "1.0.0", None, None),
133 (active, link_llvm_intrinsics, "1.0.0", Some(29602), None),
134 (active, linkage, "1.0.0", Some(29603), None),
135 (active, quote, "1.0.0", Some(29601), None),
139 (active, rustc_diagnostic_macros, "1.0.0", None, None),
140 (active, rustc_const_unstable, "1.0.0", None, None),
141 (active, box_syntax, "1.0.0", Some(49733), None),
142 (active, unboxed_closures, "1.0.0", Some(29625), None),
144 (active, fundamental, "1.0.0", Some(29635), None),
145 (active, main, "1.0.0", Some(29634), None),
146 (active, needs_allocator, "1.4.0", Some(27389), None),
147 (active, on_unimplemented, "1.0.0", Some(29628), None),
148 (active, plugin, "1.0.0", Some(29597), None),
149 (active, simd_ffi, "1.0.0", Some(27731), None),
150 (active, start, "1.0.0", Some(29633), None),
151 (active, structural_match, "1.8.0", Some(31434), None),
152 (active, panic_runtime, "1.10.0", Some(32837), None),
153 (active, needs_panic_runtime, "1.10.0", Some(32837), None),
155 // OIBIT specific features
156 (active, optin_builtin_traits, "1.0.0", Some(13231), None),
158 // Allows use of #[staged_api]
160 (active, staged_api, "1.0.0", None, None),
162 // Allows using #![no_core]
163 (active, no_core, "1.3.0", Some(29639), None),
165 // Allows using `box` in patterns; RFC 469
166 (active, box_patterns, "1.0.0", Some(29641), None),
168 // Allows using the unsafe_destructor_blind_to_params attribute;
170 (active, dropck_parametricity, "1.3.0", Some(28498), None),
172 // Allows using the may_dangle attribute; RFC 1327
173 (active, dropck_eyepatch, "1.10.0", Some(34761), None),
175 // Allows the use of custom attributes; RFC 572
176 (active, custom_attribute, "1.0.0", Some(29642), None),
178 // Allows the use of #[derive(Anything)] as sugar for
179 // #[derive_Anything].
180 (active, custom_derive, "1.0.0", Some(29644), None),
182 // Allows the use of rustc_* attributes; RFC 572
183 (active, rustc_attrs, "1.0.0", Some(29642), None),
185 // Allows the use of non lexical lifetimes; RFC 2094
186 (active, nll, "1.0.0", Some(43234), None),
188 // Allows the use of #[allow_internal_unstable]. This is an
189 // attribute on macro_rules! and can't use the attribute handling
190 // below (it has to be checked before expansion possibly makes
191 // macros disappear).
194 (active, allow_internal_unstable, "1.0.0", None, None),
196 // Allows the use of #[allow_internal_unsafe]. This is an
197 // attribute on macro_rules! and can't use the attribute handling
198 // below (it has to be checked before expansion possibly makes
199 // macros disappear).
202 (active, allow_internal_unsafe, "1.0.0", None, None),
204 // #23121. Array patterns have some hazards yet.
205 (active, slice_patterns, "1.0.0", Some(23121), None),
207 // Allows the definition of `const fn` functions.
208 (active, const_fn, "1.2.0", Some(24111), None),
210 // Allows let bindings and destructuring in `const fn` functions and constants.
211 (active, const_let, "1.22.1", Some(48821), None),
213 // Allows using #[prelude_import] on glob `use` items.
216 (active, prelude_import, "1.2.0", None, None),
218 // Allows default type parameters to influence type inference.
219 (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
221 // Allows associated type defaults
222 (active, associated_type_defaults, "1.2.0", Some(29661), None),
224 // allow `repr(simd)`, and importing the various simd intrinsics
225 (active, repr_simd, "1.4.0", Some(27731), None),
227 // allow `extern "platform-intrinsic" { ... }`
228 (active, platform_intrinsics, "1.4.0", Some(27731), None),
230 // allow `#[unwind(..)]`
231 // rustc internal for rust runtime
232 (active, unwind_attributes, "1.4.0", None, None),
234 // allow the use of `#[naked]` on functions.
235 (active, naked_functions, "1.9.0", Some(32408), None),
237 // allow `#[no_debug]`
238 (active, no_debug, "1.5.0", Some(29721), None),
240 // allow `#[omit_gdb_pretty_printer_section]`
242 (active, omit_gdb_pretty_printer_section, "1.5.0", None, None),
244 // Allows cfg(target_vendor = "...").
245 (active, cfg_target_vendor, "1.5.0", Some(29718), None),
247 // Allow attributes on expressions and non-item statements
248 (active, stmt_expr_attributes, "1.6.0", Some(15701), None),
250 // allow using type ascription in expressions
251 (active, type_ascription, "1.6.0", Some(23416), None),
253 // Allows cfg(target_thread_local)
254 (active, cfg_target_thread_local, "1.7.0", Some(29594), None),
257 (active, abi_vectorcall, "1.7.0", None, None),
260 (active, exclusive_range_pattern, "1.11.0", Some(37854), None),
262 // impl specialization (RFC 1210)
263 (active, specialization, "1.7.0", Some(31844), None),
265 // Allows cfg(target_has_atomic = "...").
266 (active, cfg_target_has_atomic, "1.9.0", Some(32976), None),
268 // The `!` type. Does not imply exhaustive_patterns (below) any more.
269 (active, never_type, "1.13.0", Some(35121), None),
271 // Allows exhaustive pattern matching on types that contain uninhabited types.
272 (active, exhaustive_patterns, "1.13.0", Some(51085), None),
274 // Allows all literals in attribute lists and values of key-value pairs.
275 (active, attr_literals, "1.13.0", Some(34981), None),
277 // Allows untagged unions `union U { ... }`
278 (active, untagged_unions, "1.13.0", Some(32836), None),
280 // Used to identify the `compiler_builtins` crate
282 (active, compiler_builtins, "1.13.0", None, None),
284 // Allows #[link(..., cfg(..))]
285 (active, link_cfg, "1.14.0", Some(37406), None),
287 (active, use_extern_macros, "1.15.0", Some(35896), None),
289 // `extern "ptx-*" fn()`
290 (active, abi_ptx, "1.15.0", Some(38788), None),
292 // The `repr(i128)` annotation for enums
293 (active, repr128, "1.16.0", Some(35118), None),
295 // The `unadjusted` ABI. Perma unstable.
297 (active, abi_unadjusted, "1.16.0", None, None),
299 // Declarative macros 2.0 (`macro`).
300 (active, decl_macro, "1.17.0", Some(39412), None),
302 // Allows #[link(kind="static-nobundle"...)]
303 (active, static_nobundle, "1.16.0", Some(37403), None),
305 // `extern "msp430-interrupt" fn()`
306 (active, abi_msp430_interrupt, "1.16.0", Some(38487), None),
308 // Used to identify crates that contain sanitizer runtimes
310 (active, sanitizer_runtime, "1.17.0", None, None),
312 // Used to identify crates that contain the profiler runtime
314 (active, profiler_runtime, "1.18.0", None, None),
316 // `extern "x86-interrupt" fn()`
317 (active, abi_x86_interrupt, "1.17.0", Some(40180), None),
320 // Allows the `catch {...}` expression
321 (active, catch_expr, "1.17.0", Some(31436), Some(Edition::Edition2018)),
323 // Used to preserve symbols (see llvm.used)
324 (active, used, "1.18.0", Some(40289), None),
326 // Allows module-level inline assembly by way of global_asm!()
327 (active, global_asm, "1.18.0", Some(35119), None),
329 // Allows overlapping impls of marker traits
330 (active, overlapping_marker_traits, "1.18.0", Some(29864), None),
332 // Allows use of the :vis macro fragment specifier
333 (active, macro_vis_matcher, "1.18.0", Some(41022), None),
336 (active, abi_thiscall, "1.19.0", None, None),
338 // Allows a test to fail without failing the whole suite
339 (active, allow_fail, "1.19.0", Some(42219), None),
341 // Allows unsized tuple coercion.
342 (active, unsized_tuple_coercion, "1.20.0", Some(42877), None),
345 (active, generators, "1.21.0", Some(43122), None),
348 (active, trait_alias, "1.24.0", Some(41517), None),
351 (active, allocator_internals, "1.20.0", None, None),
354 (active, doc_cfg, "1.21.0", Some(43781), None),
356 (active, doc_masked, "1.21.0", Some(44027), None),
358 (active, doc_spotlight, "1.22.0", Some(45040), None),
359 // #[doc(include="some-file")]
360 (active, external_doc, "1.22.0", Some(44732), None),
362 // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
363 (active, non_exhaustive, "1.22.0", Some(44109), None),
365 // `crate` as visibility modifier, synonymous to `pub(crate)`
366 (active, crate_visibility_modifier, "1.23.0", Some(45388), Some(Edition::Edition2018)),
369 (active, extern_types, "1.23.0", Some(43467), None),
371 // Allow trait methods with arbitrary self types
372 (active, arbitrary_self_types, "1.23.0", Some(44874), None),
375 (active, crate_in_paths, "1.23.0", Some(45477), Some(Edition::Edition2018)),
377 // In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
378 (active, in_band_lifetimes, "1.23.0", Some(44524), Some(Edition::Edition2018)),
380 // generic associated types (RFC 1598)
381 (active, generic_associated_types, "1.23.0", Some(44265), None),
383 // Resolve absolute paths as paths from other crates
384 (active, extern_absolute_paths, "1.24.0", Some(44660), Some(Edition::Edition2018)),
386 // `foo.rs` as an alternative to `foo/mod.rs`
387 (active, non_modrs_mods, "1.24.0", Some(44660), Some(Edition::Edition2018)),
390 (active, extern_in_paths, "1.23.0", Some(44660), None),
392 // Use `?` as the Kleene "at most one" operator
393 (active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
395 // Infer outlives requirements; RFC 2093
396 (active, infer_outlives_requirements, "1.26.0", Some(44493), None),
398 // Multiple patterns with `|` in `if let` and `while let`
399 (active, if_while_or_patterns, "1.26.0", Some(48215), None),
401 // Parentheses in patterns
402 (active, pattern_parentheses, "1.26.0", Some(51087), None),
404 // Allows `#[repr(packed)]` attribute on structs
405 (active, repr_packed, "1.26.0", Some(33158), None),
407 // `use path as _;` and `extern crate c as _;`
408 (active, underscore_imports, "1.26.0", Some(48216), None),
410 // The #[wasm_custom_section] attribute
411 (active, wasm_custom_section, "1.26.0", Some(51088), None),
413 // The #![wasm_import_module] attribute
414 (active, wasm_import_module, "1.26.0", Some(52090), None),
416 // Allows keywords to be escaped for use as identifiers
417 (active, raw_identifiers, "1.26.0", Some(48589), None),
419 // Allows macro invocations in `extern {}` blocks
420 (active, macros_in_extern, "1.27.0", Some(49476), None),
422 // `existential type`
423 (active, existential_type, "1.28.0", Some(34511), None),
425 // unstable #[target_feature] directives
426 (active, arm_target_feature, "1.27.0", Some(44839), None),
427 (active, aarch64_target_feature, "1.27.0", Some(44839), None),
428 (active, hexagon_target_feature, "1.27.0", Some(44839), None),
429 (active, powerpc_target_feature, "1.27.0", Some(44839), None),
430 (active, mips_target_feature, "1.27.0", Some(44839), None),
431 (active, avx512_target_feature, "1.27.0", Some(44839), None),
432 (active, mmx_target_feature, "1.27.0", Some(44839), None),
433 (active, sse4a_target_feature, "1.27.0", Some(44839), None),
434 (active, tbm_target_feature, "1.27.0", Some(44839), None),
436 // Allows macro invocations of the form `#[foo::bar]`
437 (active, proc_macro_path_invoc, "1.27.0", Some(38356), None),
439 // Allows macro invocations on modules expressions and statements and
440 // procedural macros to expand to non-items.
441 (active, proc_macro_mod, "1.27.0", Some(38356), None),
442 (active, proc_macro_expr, "1.27.0", Some(38356), None),
443 (active, proc_macro_non_items, "1.27.0", Some(38356), None),
444 (active, proc_macro_gen, "1.27.0", Some(38356), None),
446 // #[doc(alias = "...")]
447 (active, doc_alias, "1.27.0", Some(50146), None),
449 // Access to crate names passed via `--extern` through prelude
450 (active, extern_prelude, "1.27.0", Some(44660), Some(Edition::Edition2018)),
453 (active, tool_attributes, "1.25.0", Some(44690), None),
455 (active, tool_lints, "1.28.0", Some(44690), None),
457 // allow irrefutable patterns in if-let and while-let statements (RFC 2086)
458 (active, irrefutable_let_patterns, "1.27.0", Some(44495), None),
460 // Allows use of the :literal macro fragment specifier (RFC 1576)
461 (active, macro_literal_matcher, "1.27.0", Some(35625), None),
463 // inconsistent bounds in where clauses
464 (active, trivial_bounds, "1.28.0", Some(48214), None),
467 (active, label_break_value, "1.28.0", Some(48594), None),
469 // #[panic_implementation]
470 (active, panic_implementation, "1.28.0", Some(44489), None),
472 // #[doc(keyword = "...")]
473 (active, doc_keyword, "1.28.0", Some(51315), None),
475 // Allows async and await syntax
476 (active, async_await, "1.28.0", Some(50547), None),
478 // #[alloc_error_handler]
479 (active, alloc_error_handler, "1.29.0", Some(51540), None),
481 (active, abi_amdgpu_kernel, "1.29.0", Some(51575), None),
485 (removed, import_shadowing, "1.0.0", None, None, None),
486 (removed, managed_boxes, "1.0.0", None, None, None),
487 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
488 (removed, negate_unsigned, "1.0.0", Some(29645), None, None),
489 (removed, reflect, "1.0.0", Some(27749), None, None),
490 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
491 (removed, opt_out_copy, "1.0.0", None, None, None),
492 (removed, quad_precision_float, "1.0.0", None, None, None),
493 (removed, struct_inherit, "1.0.0", None, None, None),
494 (removed, test_removed_feature, "1.0.0", None, None, None),
495 (removed, visible_private_types, "1.0.0", None, None, None),
496 (removed, unsafe_no_drop_flag, "1.0.0", None, None, None),
497 // Allows using items which are missing stability attributes
499 (removed, unmarked_api, "1.0.0", None, None, None),
500 (removed, pushpop_unsafe, "1.2.0", None, None, None),
501 (removed, allocator, "1.0.0", None, None, None),
502 (removed, simd, "1.0.0", Some(27731), None,
503 Some("removed in favor of `#[repr(simd)]`")),
504 (removed, advanced_slice_patterns, "1.0.0", Some(23121), None,
505 Some("merged into `#![feature(slice_patterns)]`")),
506 (removed, macro_reexport, "1.0.0", Some(29638), None,
507 Some("subsumed by `#![feature(use_extern_macros)]` and `pub use`")),
511 (stable_removed, no_stack_check, "1.0.0", None, None),
515 (accepted, associated_types, "1.0.0", None, None),
516 // allow overloading augmented assignment operations like `a += b`
517 (accepted, augmented_assignments, "1.8.0", Some(28235), None),
518 // allow empty structs and enum variants with braces
519 (accepted, braced_empty_structs, "1.8.0", Some(29720), None),
520 // Allows indexing into constant arrays.
521 (accepted, const_indexing, "1.26.0", Some(29947), None),
522 (accepted, default_type_params, "1.0.0", None, None),
523 (accepted, globs, "1.0.0", None, None),
524 (accepted, if_let, "1.0.0", None, None),
525 // A temporary feature gate used to enable parser extensions needed
526 // to bootstrap fix for #5723.
527 (accepted, issue_5723_bootstrap, "1.0.0", None, None),
528 (accepted, macro_rules, "1.0.0", None, None),
529 // Allows using #![no_std]
530 (accepted, no_std, "1.6.0", None, None),
531 (accepted, slicing_syntax, "1.0.0", None, None),
532 (accepted, struct_variant, "1.0.0", None, None),
533 // These are used to test this portion of the compiler, they don't actually
535 (accepted, test_accepted_feature, "1.0.0", None, None),
536 (accepted, tuple_indexing, "1.0.0", None, None),
537 // Allows macros to appear in the type position.
538 (accepted, type_macros, "1.13.0", Some(27245), None),
539 (accepted, while_let, "1.0.0", None, None),
540 // Allows `#[deprecated]` attribute
541 (accepted, deprecated, "1.9.0", Some(29935), None),
543 (accepted, question_mark, "1.13.0", Some(31436), None),
544 // Allows `..` in tuple (struct) patterns
545 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627), None),
546 (accepted, item_like_imports, "1.15.0", Some(35120), None),
547 // Allows using `Self` and associated types in struct expressions and patterns.
548 (accepted, more_struct_aliases, "1.16.0", Some(37544), None),
549 // elide `'static` lifetimes in `static`s and `const`s
550 (accepted, static_in_const, "1.17.0", Some(35897), None),
551 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
552 (accepted, field_init_shorthand, "1.17.0", Some(37340), None),
553 // Allows the definition recursive static items.
554 (accepted, static_recursion, "1.17.0", Some(29719), None),
555 // pub(restricted) visibilities (RFC 1422)
556 (accepted, pub_restricted, "1.18.0", Some(32409), None),
557 // The #![windows_subsystem] attribute
558 (accepted, windows_subsystem, "1.18.0", Some(37499), None),
559 // Allows `break {expr}` with a value inside `loop`s.
560 (accepted, loop_break_value, "1.19.0", Some(37339), None),
561 // Permits numeric fields in struct expressions and patterns.
562 (accepted, relaxed_adts, "1.19.0", Some(35626), None),
563 // Coerces non capturing closures to function pointers
564 (accepted, closure_to_fn_coercion, "1.19.0", Some(39817), None),
565 // Allows attributes on struct literal fields.
566 (accepted, struct_field_attributes, "1.20.0", Some(38814), None),
567 // Allows the definition of associated constants in `trait` or `impl`
569 (accepted, associated_consts, "1.20.0", Some(29646), None),
570 // Usage of the `compile_error!` macro
571 (accepted, compile_error, "1.20.0", Some(40872), None),
572 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
573 (accepted, rvalue_static_promotion, "1.21.0", Some(38865), None),
574 // Allow Drop types in constants (RFC 1440)
575 (accepted, drop_types_in_const, "1.22.0", Some(33156), None),
576 // Allows the sysV64 ABI to be specified on all platforms
577 // instead of just the platforms on which it is the C ABI
578 (accepted, abi_sysv64, "1.24.0", Some(36167), None),
579 // Allows `repr(align(16))` struct attribute (RFC 1358)
580 (accepted, repr_align, "1.25.0", Some(33626), None),
581 // allow '|' at beginning of match arms (RFC 1925)
582 (accepted, match_beginning_vert, "1.25.0", Some(44101), None),
583 // Nested groups in `use` (RFC 2128)
584 (accepted, use_nested_groups, "1.25.0", Some(44494), None),
586 (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
587 // allow `..=` in patterns (RFC 1192)
588 (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
589 // Termination trait in main (RFC 1937)
590 (accepted, termination_trait, "1.26.0", Some(43301), None),
591 // Copy/Clone closures (RFC 2132)
592 (accepted, clone_closures, "1.26.0", Some(44490), None),
593 (accepted, copy_closures, "1.26.0", Some(44490), None),
594 // Allows `impl Trait` in function arguments.
595 (accepted, universal_impl_trait, "1.26.0", Some(34511), None),
596 // Allows `impl Trait` in function return types.
597 (accepted, conservative_impl_trait, "1.26.0", Some(34511), None),
599 (accepted, i128_type, "1.26.0", Some(35118), None),
600 // Default match binding modes (RFC 2005)
601 (accepted, match_default_bindings, "1.26.0", Some(42640), None),
602 // allow `'_` placeholder lifetimes
603 (accepted, underscore_lifetimes, "1.26.0", Some(44524), None),
604 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
605 (accepted, generic_param_attrs, "1.27.0", Some(48848), None),
606 // Allows cfg(target_feature = "...").
607 (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
608 // Allows #[target_feature(...)]
609 (accepted, target_feature, "1.27.0", None, None),
610 // Trait object syntax with `dyn` prefix
611 (accepted, dyn_trait, "1.27.0", Some(44662), None),
612 // allow `#[must_use]` on functions; and, must-use operators (RFC 1940)
613 (accepted, fn_must_use, "1.27.0", Some(43302), None),
614 // Allows use of the :lifetime macro fragment specifier
615 (accepted, macro_lifetime_matcher, "1.27.0", Some(34303), None),
616 // Termination trait in tests (RFC 1937)
617 (accepted, termination_trait_test, "1.27.0", Some(48854), None),
618 // The #[global_allocator] attribute
619 (accepted, global_allocator, "1.28.0", Some(27389), None),
620 // Allows `#[repr(transparent)]` attribute on newtype structs
621 (accepted, repr_transparent, "1.28.0", Some(43036), None),
622 // Defining procedural macros in `proc-macro` crates
623 (accepted, proc_macro, "1.29.0", Some(38356), None),
626 // If you change this, please modify src/doc/unstable-book as well. You must
627 // move that documentation into the relevant place in the other docs, and
628 // remove the chapter on the flag.
630 #[derive(Copy, Clone, PartialEq, Debug)]
631 pub enum AttributeType {
632 /// Normal, builtin attribute that is consumed
633 /// by the compiler before the unused_attribute check
636 /// Builtin attribute that may not be consumed by the compiler
637 /// before the unused_attribute check. These attributes
638 /// will be ignored by the unused_attribute lint
641 /// Builtin attribute that is only allowed at the crate level
645 pub enum AttributeGate {
646 /// Is gated by a given feature gate, reason
647 /// and function to check if enabled
648 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
650 /// Ungated attribute, can be used on all release channels
655 fn is_deprecated(&self) -> bool {
657 Gated(Stability::Deprecated(_), ..) => true,
663 #[derive(Copy, Clone, Debug)]
666 // Argument is tracking issue link.
667 Deprecated(&'static str),
671 impl ::std::fmt::Debug for AttributeGate {
672 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
674 Gated(ref stab, name, expl, _) =>
675 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
676 Ungated => write!(fmt, "Ungated")
681 macro_rules! cfg_fn {
682 ($field: ident) => {{
683 fn f(features: &Features) -> bool {
686 f as fn(&Features) -> bool
690 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
691 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
694 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
695 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.check_name(builtin_name))
698 // Attributes that have a special meaning to rustc or rustdoc
699 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
702 ("warn", Normal, Ungated),
703 ("allow", Normal, Ungated),
704 ("forbid", Normal, Ungated),
705 ("deny", Normal, Ungated),
707 ("macro_use", Normal, Ungated),
708 ("macro_export", Normal, Ungated),
709 ("plugin_registrar", Normal, Ungated),
711 ("cfg", Normal, Ungated),
712 ("cfg_attr", Normal, Ungated),
713 ("main", Normal, Ungated),
714 ("start", Normal, Ungated),
715 ("test", Normal, Ungated),
716 ("bench", Normal, Ungated),
717 ("repr", Normal, Ungated),
718 ("path", Normal, Ungated),
719 ("abi", Normal, Ungated),
720 ("automatically_derived", Normal, Ungated),
721 ("no_mangle", Normal, Ungated),
722 ("no_link", Normal, Ungated),
723 ("derive", Normal, Ungated),
724 ("should_panic", Normal, Ungated),
725 ("ignore", Normal, Ungated),
726 ("no_implicit_prelude", Normal, Ungated),
727 ("reexport_test_harness_main", Normal, Ungated),
728 ("link_args", Normal, Gated(Stability::Unstable,
730 "the `link_args` attribute is experimental and not \
731 portable across platforms, it is recommended to \
732 use `#[link(name = \"foo\")] instead",
733 cfg_fn!(link_args))),
734 ("macro_escape", Normal, Ungated),
737 ("structural_match", Whitelisted, Gated(Stability::Unstable,
739 "the semantics of constant patterns is \
741 cfg_fn!(structural_match))),
744 ("non_exhaustive", Whitelisted, Gated(Stability::Unstable,
746 "non exhaustive is an experimental feature",
747 cfg_fn!(non_exhaustive))),
749 ("plugin", CrateLevel, Gated(Stability::Unstable,
751 "compiler plugins are experimental \
755 ("no_std", CrateLevel, Ungated),
756 ("no_core", CrateLevel, Gated(Stability::Unstable,
758 "no_core is experimental",
760 ("lang", Normal, Gated(Stability::Unstable,
762 "language items are subject to change",
763 cfg_fn!(lang_items))),
764 ("linkage", Whitelisted, Gated(Stability::Unstable,
766 "the `linkage` attribute is experimental \
767 and not portable across platforms",
769 ("thread_local", Whitelisted, Gated(Stability::Unstable,
771 "`#[thread_local]` is an experimental feature, and does \
772 not currently handle destructors.",
773 cfg_fn!(thread_local))),
775 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
777 "the `#[rustc_on_unimplemented]` attribute \
778 is an experimental feature",
779 cfg_fn!(on_unimplemented))),
780 ("rustc_const_unstable", Normal, Gated(Stability::Unstable,
781 "rustc_const_unstable",
782 "the `#[rustc_const_unstable]` attribute \
783 is an internal feature",
784 cfg_fn!(rustc_const_unstable))),
785 ("global_allocator", Normal, Ungated),
786 ("default_lib_allocator", Whitelisted, Gated(Stability::Unstable,
787 "allocator_internals",
788 "the `#[default_lib_allocator]` \
789 attribute is an experimental feature",
790 cfg_fn!(allocator_internals))),
791 ("needs_allocator", Normal, Gated(Stability::Unstable,
792 "allocator_internals",
793 "the `#[needs_allocator]` \
794 attribute is an experimental \
796 cfg_fn!(allocator_internals))),
797 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
799 "the `#[panic_runtime]` attribute is \
800 an experimental feature",
801 cfg_fn!(panic_runtime))),
802 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
803 "needs_panic_runtime",
804 "the `#[needs_panic_runtime]` \
805 attribute is an experimental \
807 cfg_fn!(needs_panic_runtime))),
808 ("rustc_outlives", Normal, Gated(Stability::Unstable,
810 "the `#[rustc_outlives]` attribute \
811 is just used for rustc unit tests \
812 and will never be stable",
813 cfg_fn!(rustc_attrs))),
814 ("rustc_variance", Normal, Gated(Stability::Unstable,
816 "the `#[rustc_variance]` attribute \
817 is just used for rustc unit tests \
818 and will never be stable",
819 cfg_fn!(rustc_attrs))),
820 ("rustc_regions", Normal, Gated(Stability::Unstable,
822 "the `#[rustc_regions]` attribute \
823 is just used for rustc unit tests \
824 and will never be stable",
825 cfg_fn!(rustc_attrs))),
826 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
828 "the `#[rustc_error]` attribute \
829 is just used for rustc unit tests \
830 and will never be stable",
831 cfg_fn!(rustc_attrs))),
832 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
834 "the `#[rustc_if_this_changed]` attribute \
835 is just used for rustc unit tests \
836 and will never be stable",
837 cfg_fn!(rustc_attrs))),
838 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
840 "the `#[rustc_if_this_changed]` attribute \
841 is just used for rustc unit tests \
842 and will never be stable",
843 cfg_fn!(rustc_attrs))),
844 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
846 "the `#[rustc_dirty]` attribute \
847 is just used for rustc unit tests \
848 and will never be stable",
849 cfg_fn!(rustc_attrs))),
850 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
852 "the `#[rustc_clean]` attribute \
853 is just used for rustc unit tests \
854 and will never be stable",
855 cfg_fn!(rustc_attrs))),
856 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
859 is just used for rustc unit tests \
860 and will never be stable",
861 cfg_fn!(rustc_attrs))),
862 ("rustc_partition_codegened", Whitelisted, Gated(Stability::Unstable,
865 is just used for rustc unit tests \
866 and will never be stable",
867 cfg_fn!(rustc_attrs))),
868 ("rustc_synthetic", Whitelisted, Gated(Stability::Unstable,
871 is just used for rustc unit tests \
872 and will never be stable",
873 cfg_fn!(rustc_attrs))),
874 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
876 "internal rustc attributes will never be stable",
877 cfg_fn!(rustc_attrs))),
878 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
880 "internal rustc attributes will never be stable",
881 cfg_fn!(rustc_attrs))),
882 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
884 "the `#[rustc_mir]` attribute \
885 is just used for rustc unit tests \
886 and will never be stable",
887 cfg_fn!(rustc_attrs))),
888 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
890 "the `#[rustc_inherit_overflow_checks]` \
891 attribute is just used to control \
892 overflow checking behavior of several \
893 libcore functions that are inlined \
894 across crates and will never be stable",
895 cfg_fn!(rustc_attrs))),
897 ("rustc_dump_program_clauses", Whitelisted, Gated(Stability::Unstable,
899 "the `#[rustc_dump_program_clauses]` \
900 attribute is just used for rustc unit \
901 tests and will never be stable",
902 cfg_fn!(rustc_attrs))),
905 ("nll", Whitelisted, Gated(Stability::Unstable,
907 "Non lexical lifetimes",
909 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
911 "the `#[compiler_builtins]` attribute is used to \
912 identify the `compiler_builtins` crate which \
913 contains compiler-rt intrinsics and will never be \
915 cfg_fn!(compiler_builtins))),
916 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
918 "the `#[sanitizer_runtime]` attribute is used to \
919 identify crates that contain the runtime of a \
920 sanitizer and will never be stable",
921 cfg_fn!(sanitizer_runtime))),
922 ("profiler_runtime", Whitelisted, Gated(Stability::Unstable,
924 "the `#[profiler_runtime]` attribute is used to \
925 identify the `profiler_builtins` crate which \
926 contains the profiler runtime and will never be \
928 cfg_fn!(profiler_runtime))),
930 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
931 "allow_internal_unstable",
932 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
933 cfg_fn!(allow_internal_unstable))),
935 ("allow_internal_unsafe", Normal, Gated(Stability::Unstable,
936 "allow_internal_unsafe",
937 EXPLAIN_ALLOW_INTERNAL_UNSAFE,
938 cfg_fn!(allow_internal_unsafe))),
940 ("fundamental", Whitelisted, Gated(Stability::Unstable,
942 "the `#[fundamental]` attribute \
943 is an experimental feature",
944 cfg_fn!(fundamental))),
946 ("proc_macro_derive", Normal, Ungated),
948 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
950 "internal implementation detail",
951 cfg_fn!(rustc_attrs))),
953 // FIXME: #14408 whitelist docs since rustdoc looks at them
954 ("doc", Whitelisted, Ungated),
956 // FIXME: #14406 these are processed in codegen, which happens after the
958 ("cold", Whitelisted, Ungated),
959 ("naked", Whitelisted, Gated(Stability::Unstable,
961 "the `#[naked]` attribute \
962 is an experimental feature",
963 cfg_fn!(naked_functions))),
964 ("target_feature", Whitelisted, Ungated),
965 ("export_name", Whitelisted, Ungated),
966 ("inline", Whitelisted, Ungated),
967 ("link", Whitelisted, Ungated),
968 ("link_name", Whitelisted, Ungated),
969 ("link_section", Whitelisted, Ungated),
970 ("no_builtins", Whitelisted, Ungated),
971 ("no_mangle", Whitelisted, Ungated),
972 ("no_debug", Whitelisted, Gated(
973 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
975 "the `#[no_debug]` attribute was an experimental feature that has been \
976 deprecated due to lack of demand",
978 ("wasm_import_module", Normal, Gated(Stability::Unstable,
979 "wasm_import_module",
980 "experimental attribute",
981 cfg_fn!(wasm_import_module))),
982 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
983 "omit_gdb_pretty_printer_section",
984 "the `#[omit_gdb_pretty_printer_section]` \
985 attribute is just used for the Rust test \
987 cfg_fn!(omit_gdb_pretty_printer_section))),
988 ("unsafe_destructor_blind_to_params",
990 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761"),
991 "dropck_parametricity",
992 "unsafe_destructor_blind_to_params has been replaced by \
993 may_dangle and will be removed in the future",
994 cfg_fn!(dropck_parametricity))),
997 Gated(Stability::Unstable,
999 "may_dangle has unstable semantics and may be removed in the future",
1000 cfg_fn!(dropck_eyepatch))),
1001 ("unwind", Whitelisted, Gated(Stability::Unstable,
1002 "unwind_attributes",
1003 "#[unwind] is experimental",
1004 cfg_fn!(unwind_attributes))),
1005 ("used", Whitelisted, Gated(
1006 Stability::Unstable, "used",
1007 "the `#[used]` attribute is an experimental feature",
1011 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
1013 "`#[prelude_import]` is for use by rustc only",
1014 cfg_fn!(prelude_import))),
1016 // FIXME: #14407 these are only looked at on-demand so we can't
1017 // guarantee they'll have already been checked
1018 ("rustc_deprecated", Whitelisted, Ungated),
1019 ("must_use", Whitelisted, Ungated),
1020 ("stable", Whitelisted, Ungated),
1021 ("unstable", Whitelisted, Ungated),
1022 ("deprecated", Normal, Ungated),
1024 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
1026 "unboxed_closures are still evolving",
1027 cfg_fn!(unboxed_closures))),
1029 ("windows_subsystem", Whitelisted, Ungated),
1031 ("proc_macro_attribute", Normal, Ungated),
1032 ("proc_macro", Normal, Ungated),
1034 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
1035 "rustc_derive_registrar",
1036 "used internally by rustc",
1037 cfg_fn!(rustc_attrs))),
1039 ("allow_fail", Normal, Gated(Stability::Unstable,
1041 "allow_fail attribute is currently unstable",
1042 cfg_fn!(allow_fail))),
1044 ("rustc_std_internal_symbol", Whitelisted, Gated(Stability::Unstable,
1046 "this is an internal attribute that will \
1048 cfg_fn!(rustc_attrs))),
1050 // whitelists "identity-like" conversion methods to suggest on type mismatch
1051 ("rustc_conversion_suggestion", Whitelisted, Gated(Stability::Unstable,
1053 "this is an internal attribute that will \
1055 cfg_fn!(rustc_attrs))),
1057 ("rustc_args_required_const", Whitelisted, Gated(Stability::Unstable,
1059 "never will be stable",
1060 cfg_fn!(rustc_attrs))),
1063 ("infer_outlives_requirements", Normal, Gated(Stability::Unstable,
1064 "infer_outlives_requirements",
1065 "infer outlives requirements is an experimental feature",
1066 cfg_fn!(infer_outlives_requirements))),
1068 ("wasm_custom_section", Whitelisted, Gated(Stability::Unstable,
1069 "wasm_custom_section",
1070 "attribute is currently unstable",
1071 cfg_fn!(wasm_custom_section))),
1074 ("panic_implementation", Normal, Gated(Stability::Unstable,
1075 "panic_implementation",
1076 "#[panic_implementation] is an unstable feature",
1077 cfg_fn!(panic_implementation))),
1079 ("alloc_error_handler", Normal, Gated(Stability::Unstable,
1080 "alloc_error_handler",
1081 "#[alloc_error_handler] is an unstable feature",
1082 cfg_fn!(alloc_error_handler))),
1084 // Crate level attributes
1085 ("crate_name", CrateLevel, Ungated),
1086 ("crate_type", CrateLevel, Ungated),
1087 ("crate_id", CrateLevel, Ungated),
1088 ("feature", CrateLevel, Ungated),
1089 ("no_start", CrateLevel, Ungated),
1090 ("no_main", CrateLevel, Ungated),
1091 ("no_builtins", CrateLevel, Ungated),
1092 ("recursion_limit", CrateLevel, Ungated),
1093 ("type_length_limit", CrateLevel, Ungated),
1096 // cfg(...)'s that are feature gated
1097 const GATED_CFGS: &[(&str, &str, fn(&Features) -> bool)] = &[
1098 // (name in cfg, feature, function to check if the feature is enabled)
1099 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
1100 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
1101 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
1105 pub struct GatedCfg {
1111 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
1112 let name = cfg.name().as_str();
1114 .position(|info| info.0 == name)
1123 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
1124 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
1125 if !has_feature(features) && !self.span.allows_unstable() {
1126 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
1127 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
1132 struct Context<'a> {
1133 features: &'a Features,
1134 parse_sess: &'a ParseSess,
1135 plugin_attributes: &'a [(String, AttributeType)],
1138 macro_rules! gate_feature_fn {
1139 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
1140 let (cx, has_feature, span,
1141 name, explain, level) = ($cx, $has_feature, $span, $name, $explain, $level);
1142 let has_feature: bool = has_feature(&$cx.features);
1143 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
1144 if !has_feature && !span.allows_unstable() {
1145 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
1151 macro_rules! gate_feature {
1152 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
1153 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1154 stringify!($feature), $explain, GateStrength::Hard)
1156 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
1157 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
1158 stringify!($feature), $explain, $level)
1162 impl<'a> Context<'a> {
1163 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
1164 debug!("check_attribute(attr = {:?})", attr);
1165 let name = attr.name().as_str();
1166 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
1168 if let Gated(_, name, desc, ref has_feature) = *gateage {
1169 gate_feature_fn!(self, has_feature, attr.span, name, desc, GateStrength::Hard);
1170 } else if name == "doc" {
1171 if let Some(content) = attr.meta_item_list() {
1172 if content.iter().any(|c| c.check_name("include")) {
1173 gate_feature!(self, external_doc, attr.span,
1174 "#[doc(include = \"...\")] is experimental"
1179 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
1183 for &(ref n, ref ty) in self.plugin_attributes {
1184 if attr.path == &**n {
1185 // Plugins can't gate attributes, so we don't check for it
1186 // unlike the code above; we only use this loop to
1187 // short-circuit to avoid the checks below
1188 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
1192 if name.starts_with("rustc_") {
1193 gate_feature!(self, rustc_attrs, attr.span,
1194 "unless otherwise specified, attributes \
1195 with the prefix `rustc_` \
1196 are reserved for internal compiler diagnostics");
1197 } else if name.starts_with("derive_") {
1198 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
1199 } else if !attr::is_known(attr) {
1200 // Only run the custom attribute lint during regular
1201 // feature gate checking. Macro gating runs
1202 // before the plugin attributes are registered
1203 // so we skip this then
1205 if attr.is_scoped() {
1206 gate_feature!(self, tool_attributes, attr.span,
1207 &format!("scoped attribute `{}` is experimental", attr.path));
1208 if attr::is_known_tool(attr) {
1209 attr::mark_used(attr);
1212 self.parse_sess.span_diagnostic,
1215 "an unknown tool name found in scoped attribute: `{}`.",
1220 gate_feature!(self, custom_attribute, attr.span,
1221 &format!("The attribute `{}` is currently \
1222 unknown to the compiler and \
1224 added to it in the future",
1232 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
1233 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
1234 cx.check_attribute(attr, true);
1237 pub fn find_lang_feature_accepted_version(feature: &str) -> Option<&'static str> {
1238 ACCEPTED_FEATURES.iter().find(|t| t.0 == feature).map(|t| t.1)
1241 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
1242 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
1244 // FIXME (#28244): enforce that active features have issue numbers
1245 // assert!(issue.is_some())
1248 // search in Accepted, Removed, or Stable Removed features
1249 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
1250 .find(|t| t.0 == feature);
1252 Some(&(_, _, issue, _)) => issue,
1253 None => panic!("Feature `{}` is not declared anywhere", feature),
1258 pub enum GateIssue {
1260 Library(Option<u32>)
1263 #[derive(Debug, Copy, Clone, PartialEq)]
1264 pub enum GateStrength {
1265 /// A hard error. (Most feature gates should use this.)
1267 /// Only a warning. (Use this only as backwards-compatibility demands.)
1271 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
1273 feature_err(sess, feature, span, issue, explain).emit();
1276 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1277 explain: &str) -> DiagnosticBuilder<'a> {
1278 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
1281 fn leveled_feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
1282 explain: &str, level: GateStrength) -> DiagnosticBuilder<'a> {
1283 let diag = &sess.span_diagnostic;
1285 let issue = match issue {
1286 GateIssue::Language => find_lang_feature_issue(feature),
1287 GateIssue::Library(lib) => lib,
1290 let explanation = match issue {
1291 None | Some(0) => explain.to_owned(),
1292 Some(n) => format!("{} (see issue #{})", explain, n)
1295 let mut err = match level {
1296 GateStrength::Hard => {
1297 diag.struct_span_err_with_code(span, &explanation, stringify_error_code!(E0658))
1299 GateStrength::Soft => diag.struct_span_warn(span, &explanation),
1302 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1303 if sess.unstable_features.is_nightly_build() {
1304 err.help(&format!("add #![feature({})] to the \
1305 crate attributes to enable",
1309 // If we're on stable and only emitting a "soft" warning, add a note to
1310 // clarify that the feature isn't "on" (rather than being on but
1312 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
1313 err.help("a nightly build of the compiler is required to enable this feature");
1320 const EXPLAIN_BOX_SYNTAX: &'static str =
1321 "box expression syntax is experimental; you can call `Box::new` instead.";
1323 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
1324 "attributes on expressions are experimental.";
1326 pub const EXPLAIN_ASM: &'static str =
1327 "inline assembly is not stable enough for use and is subject to change";
1329 pub const EXPLAIN_GLOBAL_ASM: &'static str =
1330 "`global_asm!` is not stable enough for use and is subject to change";
1332 pub const EXPLAIN_LOG_SYNTAX: &'static str =
1333 "`log_syntax!` is not stable enough for use and is subject to change";
1335 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
1336 "`concat_idents` is not stable enough for use and is subject to change";
1338 pub const EXPLAIN_TRACE_MACROS: &'static str =
1339 "`trace_macros` is not stable enough for use and is subject to change";
1340 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
1341 "allow_internal_unstable side-steps feature gating and stability checks";
1342 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &'static str =
1343 "allow_internal_unsafe side-steps the unsafe_code lint";
1345 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
1346 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1348 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
1349 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1350 Prefer using procedural macro custom derive.";
1352 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
1353 "attributes of the form `#[derive_*]` are reserved for the compiler";
1355 pub const EXPLAIN_VIS_MATCHER: &'static str =
1356 ":vis fragment specifier is experimental and subject to change";
1358 pub const EXPLAIN_LITERAL_MATCHER: &'static str =
1359 ":literal fragment specifier is experimental and subject to change";
1361 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
1362 "unsized tuple coercion is not stable enough for use and is subject to change";
1364 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
1365 "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1367 pub const EXPLAIN_MACROS_IN_EXTERN: &'static str =
1368 "macro invocations in `extern {}` blocks are experimental.";
1370 // mention proc-macros when enabled
1371 pub const EXPLAIN_PROC_MACROS_IN_EXTERN: &'static str =
1372 "macro and proc-macro invocations in `extern {}` blocks are experimental.";
1374 struct PostExpansionVisitor<'a> {
1375 context: &'a Context<'a>,
1378 macro_rules! gate_feature_post {
1379 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1380 let (cx, span) = ($cx, $span);
1381 if !span.allows_unstable() {
1382 gate_feature!(cx.context, $feature, span, $explain)
1385 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
1386 let (cx, span) = ($cx, $span);
1387 if !span.allows_unstable() {
1388 gate_feature!(cx.context, $feature, span, $explain, $level)
1393 impl<'a> PostExpansionVisitor<'a> {
1394 fn check_abi(&self, abi: Abi, span: Span) {
1396 Abi::RustIntrinsic => {
1397 gate_feature_post!(&self, intrinsics, span,
1398 "intrinsics are subject to change");
1400 Abi::PlatformIntrinsic => {
1401 gate_feature_post!(&self, platform_intrinsics, span,
1402 "platform intrinsics are experimental and possibly buggy");
1404 Abi::Vectorcall => {
1405 gate_feature_post!(&self, abi_vectorcall, span,
1406 "vectorcall is experimental and subject to change");
1409 gate_feature_post!(&self, abi_thiscall, span,
1410 "thiscall is experimental and subject to change");
1413 gate_feature_post!(&self, unboxed_closures, span,
1414 "rust-call ABI is subject to change");
1417 gate_feature_post!(&self, abi_ptx, span,
1418 "PTX ABIs are experimental and subject to change");
1420 Abi::Unadjusted => {
1421 gate_feature_post!(&self, abi_unadjusted, span,
1422 "unadjusted ABI is an implementation detail and perma-unstable");
1424 Abi::Msp430Interrupt => {
1425 gate_feature_post!(&self, abi_msp430_interrupt, span,
1426 "msp430-interrupt ABI is experimental and subject to change");
1428 Abi::X86Interrupt => {
1429 gate_feature_post!(&self, abi_x86_interrupt, span,
1430 "x86-interrupt ABI is experimental and subject to change");
1432 Abi::AmdGpuKernel => {
1433 gate_feature_post!(&self, abi_amdgpu_kernel, span,
1434 "amdgpu-kernel ABI is experimental and subject to change");
1450 fn contains_novel_literal(item: &ast::MetaItem) -> bool {
1451 use ast::MetaItemKind::*;
1452 use ast::NestedMetaItemKind::*;
1456 NameValue(ref lit) => !lit.node.is_str(),
1457 List(ref list) => list.iter().any(|li| {
1459 MetaItem(ref mi) => contains_novel_literal(mi),
1466 impl<'a> PostExpansionVisitor<'a> {
1467 fn whole_crate_feature_gates(&mut self, _krate: &ast::Crate) {
1468 for &(ident, span) in &*self.context.parse_sess.non_modrs_mods.borrow() {
1469 if !span.allows_unstable() {
1470 let cx = &self.context;
1471 let level = GateStrength::Hard;
1472 let has_feature = cx.features.non_modrs_mods;
1473 let name = "non_modrs_mods";
1474 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}",
1475 name, span, has_feature);
1477 if !has_feature && !span.allows_unstable() {
1478 leveled_feature_err(
1479 cx.parse_sess, name, span, GateIssue::Language,
1480 "mod statements in non-mod.rs files are unstable", level
1482 .help(&format!("on stable builds, rename this file to {}{}mod.rs",
1483 ident, path::MAIN_SEPARATOR))
1491 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1492 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1493 if !attr.span.allows_unstable() {
1494 // check for gated attributes
1495 self.context.check_attribute(attr, false);
1498 if attr.check_name("doc") {
1499 if let Some(content) = attr.meta_item_list() {
1500 if content.len() == 1 && content[0].check_name("cfg") {
1501 gate_feature_post!(&self, doc_cfg, attr.span,
1502 "#[doc(cfg(...))] is experimental"
1504 } else if content.iter().any(|c| c.check_name("masked")) {
1505 gate_feature_post!(&self, doc_masked, attr.span,
1506 "#[doc(masked)] is experimental"
1508 } else if content.iter().any(|c| c.check_name("spotlight")) {
1509 gate_feature_post!(&self, doc_spotlight, attr.span,
1510 "#[doc(spotlight)] is experimental"
1512 } else if content.iter().any(|c| c.check_name("alias")) {
1513 gate_feature_post!(&self, doc_alias, attr.span,
1514 "#[doc(alias = \"...\")] is experimental"
1516 } else if content.iter().any(|c| c.check_name("keyword")) {
1517 gate_feature_post!(&self, doc_keyword, attr.span,
1518 "#[doc(keyword = \"...\")] is experimental"
1524 // allow attr_literals in #[repr(align(x))] and #[repr(packed(n))]
1525 let mut allow_attr_literal = false;
1526 if attr.path == "repr" {
1527 if let Some(content) = attr.meta_item_list() {
1528 allow_attr_literal = content.iter().any(
1529 |c| c.check_name("align") || c.check_name("packed"));
1533 if self.context.features.use_extern_macros && attr::is_known(attr) {
1537 if !allow_attr_literal {
1538 let meta = panictry!(attr.parse_meta(self.context.parse_sess));
1539 if contains_novel_literal(&meta) {
1540 gate_feature_post!(&self, attr_literals, attr.span,
1541 "non-string literals in attributes, or string \
1542 literals in top-level positions, are experimental");
1547 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1548 if !name.as_str().is_ascii() {
1549 gate_feature_post!(&self,
1551 self.context.parse_sess.codemap().def_span(sp),
1552 "non-ascii idents are not fully supported.");
1556 fn visit_use_tree(&mut self, use_tree: &'a ast::UseTree, id: NodeId, _nested: bool) {
1557 if let ast::UseTreeKind::Simple(Some(ident), ..) = use_tree.kind {
1558 if ident.name == "_" {
1559 gate_feature_post!(&self, underscore_imports, use_tree.span,
1560 "renaming imports with `_` is unstable");
1564 visit::walk_use_tree(self, use_tree, id);
1567 fn visit_item(&mut self, i: &'a ast::Item) {
1569 ast::ItemKind::ExternCrate(_) => {
1570 if i.ident.name == "_" {
1571 gate_feature_post!(&self, underscore_imports, i.span,
1572 "renaming extern crates with `_` is unstable");
1576 ast::ItemKind::ForeignMod(ref foreign_module) => {
1577 self.check_abi(foreign_module.abi, i.span);
1580 ast::ItemKind::Fn(..) => {
1581 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1582 gate_feature_post!(&self, plugin_registrar, i.span,
1583 "compiler plugins are experimental and possibly buggy");
1585 if attr::contains_name(&i.attrs[..], "start") {
1586 gate_feature_post!(&self, start, i.span,
1587 "a #[start] function is an experimental \
1588 feature whose signature may change \
1591 if attr::contains_name(&i.attrs[..], "main") {
1592 gate_feature_post!(&self, main, i.span,
1593 "declaration of a nonstandard #[main] \
1594 function may change over time, for now \
1595 a top-level `fn main()` is required");
1599 ast::ItemKind::Struct(..) => {
1600 if let Some(attr) = attr::find_by_name(&i.attrs[..], "repr") {
1601 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1602 if item.check_name("simd") {
1603 gate_feature_post!(&self, repr_simd, attr.span,
1604 "SIMD types are experimental and possibly buggy");
1606 if let Some((name, _)) = item.name_value_literal() {
1607 if name == "packed" {
1608 gate_feature_post!(&self, repr_packed, attr.span,
1609 "the `#[repr(packed(n))]` attribute \
1617 ast::ItemKind::TraitAlias(..) => {
1618 gate_feature_post!(&self, trait_alias,
1620 "trait aliases are not yet fully implemented");
1623 ast::ItemKind::Impl(_, polarity, defaultness, _, _, _, _) => {
1624 if polarity == ast::ImplPolarity::Negative {
1625 gate_feature_post!(&self, optin_builtin_traits,
1627 "negative trait bounds are not yet fully implemented; \
1628 use marker types for now");
1631 if let ast::Defaultness::Default = defaultness {
1632 gate_feature_post!(&self, specialization,
1634 "specialization is unstable");
1638 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
1639 gate_feature_post!(&self, optin_builtin_traits,
1641 "auto traits are experimental and possibly buggy");
1644 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
1645 let msg = "`macro` is experimental";
1646 gate_feature_post!(&self, decl_macro, i.span, msg);
1649 ast::ItemKind::Existential(..) => {
1654 "existential types are unstable"
1661 visit::walk_item(self, i);
1664 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1666 ast::ForeignItemKind::Fn(..) |
1667 ast::ForeignItemKind::Static(..) => {
1668 let link_name = attr::first_attr_value_str_by_name(&i.attrs, "link_name");
1669 let links_to_llvm = match link_name {
1670 Some(val) => val.as_str().starts_with("llvm."),
1674 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1675 "linking to LLVM intrinsics is experimental");
1678 ast::ForeignItemKind::Ty => {
1679 gate_feature_post!(&self, extern_types, i.span,
1680 "extern types are experimental");
1682 ast::ForeignItemKind::Macro(..) => {}
1685 visit::walk_foreign_item(self, i)
1688 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1690 ast::TyKind::BareFn(ref bare_fn_ty) => {
1691 self.check_abi(bare_fn_ty.abi, ty.span);
1693 ast::TyKind::Never => {
1694 gate_feature_post!(&self, never_type, ty.span,
1695 "The `!` type is experimental");
1699 visit::walk_ty(self, ty)
1702 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1703 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1704 if let ast::TyKind::Never = output_ty.node {
1707 self.visit_ty(output_ty)
1712 fn visit_expr(&mut self, e: &'a ast::Expr) {
1714 ast::ExprKind::Box(_) => {
1715 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1717 ast::ExprKind::Type(..) => {
1718 gate_feature_post!(&self, type_ascription, e.span,
1719 "type ascription is experimental");
1721 ast::ExprKind::ObsoleteInPlace(..) => {
1722 // these get a hard error in ast-validation
1724 ast::ExprKind::Yield(..) => {
1725 gate_feature_post!(&self, generators,
1727 "yield syntax is experimental");
1729 ast::ExprKind::Catch(_) => {
1730 gate_feature_post!(&self, catch_expr, e.span, "`catch` expression is experimental");
1732 ast::ExprKind::IfLet(ref pats, ..) | ast::ExprKind::WhileLet(ref pats, ..) => {
1734 gate_feature_post!(&self, if_while_or_patterns, e.span,
1735 "multiple patterns in `if let` and `while let` are unstable");
1738 ast::ExprKind::Block(_, opt_label) => {
1739 if let Some(label) = opt_label {
1740 gate_feature_post!(&self, label_break_value, label.ident.span,
1741 "labels on blocks are unstable");
1744 ast::ExprKind::Closure(_, ast::IsAsync::Async { .. }, ..) => {
1745 gate_feature_post!(&self, async_await, e.span, "async closures are unstable");
1747 ast::ExprKind::Async(..) => {
1748 gate_feature_post!(&self, async_await, e.span, "async blocks are unstable");
1752 visit::walk_expr(self, e);
1755 fn visit_arm(&mut self, arm: &'a ast::Arm) {
1756 visit::walk_arm(self, arm)
1759 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1760 match pattern.node {
1761 PatKind::Slice(_, Some(ref subslice), _) => {
1762 gate_feature_post!(&self, slice_patterns,
1764 "syntax for subslices in slice patterns is not yet stabilized");
1766 PatKind::Box(..) => {
1767 gate_feature_post!(&self, box_patterns,
1769 "box pattern syntax is experimental");
1771 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
1772 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1773 "exclusive range pattern syntax is experimental");
1775 PatKind::Paren(..) => {
1776 gate_feature_post!(&self, pattern_parentheses, pattern.span,
1777 "parentheses in patterns are unstable");
1781 visit::walk_pat(self, pattern)
1784 fn visit_fn(&mut self,
1785 fn_kind: FnKind<'a>,
1786 fn_decl: &'a ast::FnDecl,
1790 FnKind::ItemFn(_, header, _, _) => {
1791 // check for const fn and async fn declarations
1792 if header.asyncness.is_async() {
1793 gate_feature_post!(&self, async_await, span, "async fn is unstable");
1795 if header.constness.node == ast::Constness::Const {
1796 gate_feature_post!(&self, const_fn, span, "const fn is unstable");
1798 // stability of const fn methods are covered in
1799 // visit_trait_item and visit_impl_item below; this is
1800 // because default methods don't pass through this
1803 self.check_abi(header.abi, span);
1805 FnKind::Method(_, sig, _, _) => {
1806 self.check_abi(sig.header.abi, span);
1810 visit::walk_fn(self, fn_kind, fn_decl, span);
1813 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1815 ast::TraitItemKind::Method(ref sig, ref block) => {
1816 if block.is_none() {
1817 self.check_abi(sig.header.abi, ti.span);
1819 if sig.header.constness.node == ast::Constness::Const {
1820 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1823 ast::TraitItemKind::Type(_, ref default) => {
1824 // We use three if statements instead of something like match guards so that all
1825 // of these errors can be emitted if all cases apply.
1826 if default.is_some() {
1827 gate_feature_post!(&self, associated_type_defaults, ti.span,
1828 "associated type defaults are unstable");
1830 if !ti.generics.params.is_empty() {
1831 gate_feature_post!(&self, generic_associated_types, ti.span,
1832 "generic associated types are unstable");
1834 if !ti.generics.where_clause.predicates.is_empty() {
1835 gate_feature_post!(&self, generic_associated_types, ti.span,
1836 "where clauses on associated types are unstable");
1841 visit::walk_trait_item(self, ti);
1844 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1845 if ii.defaultness == ast::Defaultness::Default {
1846 gate_feature_post!(&self, specialization,
1848 "specialization is unstable");
1852 ast::ImplItemKind::Method(ref sig, _) => {
1853 if sig.header.constness.node == ast::Constness::Const {
1854 gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable");
1857 ast::ImplItemKind::Existential(..) => {
1862 "existential types are unstable"
1866 ast::ImplItemKind::Type(_) if !ii.generics.params.is_empty() => {
1867 gate_feature_post!(&self, generic_associated_types, ii.span,
1868 "generic associated types are unstable");
1872 visit::walk_impl_item(self, ii);
1875 fn visit_path(&mut self, path: &'a ast::Path, _id: NodeId) {
1876 for segment in &path.segments {
1877 // Identifiers we are going to check could come from a legacy macro (e.g. `#[test]`).
1878 // For such macros identifiers must have empty context, because this context is
1879 // used during name resolution and produced names must be unhygienic for compatibility.
1880 // On the other hand, we need the actual non-empty context for feature gate checking
1881 // because it's hygienic even for legacy macros. As previously stated, such context
1882 // cannot be kept in identifiers, so it's kept in paths instead and we take it from
1883 // there while keeping location info from the ident span.
1884 let span = segment.ident.span.with_ctxt(path.span.ctxt());
1885 if segment.ident.name == keywords::Crate.name() {
1886 gate_feature_post!(&self, crate_in_paths, span,
1887 "`crate` in paths is experimental");
1888 } else if segment.ident.name == keywords::Extern.name() {
1889 gate_feature_post!(&self, extern_in_paths, span,
1890 "`extern` in paths is experimental");
1894 visit::walk_path(self, path);
1897 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
1898 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
1899 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
1900 "`crate` visibility modifier is experimental");
1902 visit::walk_vis(self, vis);
1906 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
1907 crate_edition: Edition) -> Features {
1908 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
1909 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
1910 if let Some(reason) = reason {
1911 err.span_note(span, reason);
1916 let mut features = Features::new();
1918 let mut feature_checker = FeatureChecker::default();
1920 for &(.., f_edition, set) in ACTIVE_FEATURES.iter() {
1921 if let Some(f_edition) = f_edition {
1922 if f_edition <= crate_edition {
1923 set(&mut features, DUMMY_SP);
1928 for attr in krate_attrs {
1929 if !attr.check_name("feature") {
1933 let list = match attr.meta_item_list() {
1936 span_err!(span_handler, attr.span, E0555,
1937 "malformed feature attribute, expected #![feature(...)]");
1943 let name = if let Some(word) = mi.word() {
1946 span_err!(span_handler, mi.span, E0556,
1947 "malformed feature, expected just one word");
1951 if let Some((.., set)) = ACTIVE_FEATURES.iter().find(|f| name == f.0) {
1952 set(&mut features, mi.span);
1953 feature_checker.collect(&features, mi.span);
1957 let removed = REMOVED_FEATURES.iter().find(|f| name == f.0);
1958 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.0);
1959 if let Some((.., reason)) = removed.or(stable_removed) {
1960 feature_removed(span_handler, mi.span, *reason);
1964 if ACCEPTED_FEATURES.iter().any(|f| name == f.0) {
1965 features.declared_stable_lang_features.push((name, mi.span));
1969 if let Some(edition) = ALL_EDITIONS.iter().find(|e| name == e.feature_name()) {
1970 if *edition <= crate_edition {
1974 for &(.., f_edition, set) in ACTIVE_FEATURES.iter() {
1975 if let Some(f_edition) = f_edition {
1976 if *edition >= f_edition {
1977 // FIXME(Manishearth) there is currently no way to set
1978 // lib features by edition
1979 set(&mut features, DUMMY_SP);
1987 features.declared_lib_features.push((name, mi.span));
1991 feature_checker.check(span_handler);
1996 /// A collector for mutually exclusive and interdependent features and their flag spans.
1998 struct FeatureChecker {
1999 use_extern_macros: Option<Span>,
2000 custom_attribute: Option<Span>,
2003 impl FeatureChecker {
2004 // If this method turns out to be a hotspot due to branching,
2005 // the branching can be eliminated by modifying `set!()` to set these spans
2006 // only for the features that need to be checked for mutual exclusion.
2007 fn collect(&mut self, features: &Features, span: Span) {
2008 if features.use_extern_macros {
2009 // If self.use_extern_macros is None, set to Some(span)
2010 self.use_extern_macros = self.use_extern_macros.or(Some(span));
2013 if features.custom_attribute {
2014 self.custom_attribute = self.custom_attribute.or(Some(span));
2018 fn check(self, handler: &Handler) {
2019 if let (Some(pm_span), Some(ca_span)) = (self.use_extern_macros, self.custom_attribute) {
2020 handler.struct_span_err(pm_span, "Cannot use `#![feature(use_extern_macros)]` and \
2021 `#![feature(custom_attribute)] at the same time")
2022 .span_note(ca_span, "`#![feature(custom_attribute)]` declared here")
2030 pub fn check_crate(krate: &ast::Crate,
2032 features: &Features,
2033 plugin_attributes: &[(String, AttributeType)],
2034 unstable: UnstableFeatures) {
2035 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
2042 if !features.raw_identifiers {
2043 for &span in sess.raw_identifier_spans.borrow().iter() {
2044 if !span.allows_unstable() {
2045 gate_feature!(&ctx, raw_identifiers, span,
2046 "raw identifiers are experimental and subject to change"
2052 let visitor = &mut PostExpansionVisitor { context: &ctx };
2053 visitor.whole_crate_feature_gates(krate);
2054 visit::walk_crate(visitor, krate);
2057 #[derive(Clone, Copy, Hash)]
2058 pub enum UnstableFeatures {
2059 /// Hard errors for unstable features are active, as on
2060 /// beta/stable channels.
2062 /// Allow features to be activated, as on nightly.
2064 /// Errors are bypassed for bootstrapping. This is required any time
2065 /// during the build that feature-related lints are set to warn or above
2066 /// because the build turns on warnings-as-errors and uses lots of unstable
2067 /// features. As a result, this is always required for building Rust itself.
2071 impl UnstableFeatures {
2072 pub fn from_environment() -> UnstableFeatures {
2073 // Whether this is a feature-staged build, i.e. on the beta or stable channel
2074 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
2075 // Whether we should enable unstable features for bootstrapping
2076 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
2077 match (disable_unstable_features, bootstrap) {
2078 (_, true) => UnstableFeatures::Cheat,
2079 (true, _) => UnstableFeatures::Disallow,
2080 (false, _) => UnstableFeatures::Allow
2084 pub fn is_nightly_build(&self) -> bool {
2086 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
2092 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
2093 unstable: UnstableFeatures) {
2094 let allow_features = match unstable {
2095 UnstableFeatures::Allow => true,
2096 UnstableFeatures::Disallow => false,
2097 UnstableFeatures::Cheat => true
2099 if !allow_features {
2100 for attr in &krate.attrs {
2101 if attr.check_name("feature") {
2102 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2103 span_err!(span_handler, attr.span, E0554,
2104 "#![feature] may not be used on the {} release channel",