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::*;
29 use ast::{self, NodeId, PatKind, RangeEnd};
33 use errors::{DiagnosticBuilder, Handler, FatalError};
34 use visit::{self, FnKind, Visitor};
38 use std::ascii::AsciiExt;
43 fn f(features: &mut Features) -> &mut bool {
46 f as fn(&mut Features) -> &mut bool
50 macro_rules! declare_features {
51 ($((active, $feature: ident, $ver: expr, $issue: expr),)+) => {
52 /// Represents active features that are currently being implemented or
53 /// currently being considered for addition/removal.
54 const ACTIVE_FEATURES: &'static [(&'static str, &'static str,
55 Option<u32>, fn(&mut Features) -> &mut bool)] = &[
56 $((stringify!($feature), $ver, $issue, setter!($feature))),+
59 /// A set of features to be used by later passes.
61 /// #![feature] attrs for stable language features, for error reporting
62 pub declared_stable_lang_features: Vec<(Symbol, Span)>,
63 /// #![feature] attrs for non-language (library) features
64 pub declared_lib_features: Vec<(Symbol, Span)>,
65 $(pub $feature: bool),+
69 pub fn new() -> Features {
71 declared_stable_lang_features: Vec::new(),
72 declared_lib_features: Vec::new(),
79 ($((removed, $feature: ident, $ver: expr, $issue: expr),)+) => {
80 /// Represents unstable features which have since been removed (it was once Active)
81 const REMOVED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
82 $((stringify!($feature), $ver, $issue)),+
86 ($((stable_removed, $feature: ident, $ver: expr, $issue: expr),)+) => {
87 /// Represents stable features which have since been removed (it was once Accepted)
88 const STABLE_REMOVED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
89 $((stringify!($feature), $ver, $issue)),+
93 ($((accepted, $feature: ident, $ver: expr, $issue: expr),)+) => {
94 /// Those language feature has since been Accepted (it was once Active)
95 const ACCEPTED_FEATURES: &'static [(&'static str, &'static str, Option<u32>)] = &[
96 $((stringify!($feature), $ver, $issue)),+
101 // If you change this, please modify src/doc/unstable-book as well.
103 // Don't ever remove anything from this list; set them to 'Removed'.
105 // The version numbers here correspond to the version in which the current status
106 // was set. This is most important for knowing when a particular feature became
109 // NB: The featureck.py script parses this information directly out of the source
110 // so take care when modifying it.
113 (active, asm, "1.0.0", Some(29722)),
114 (active, concat_idents, "1.0.0", Some(29599)),
115 (active, link_args, "1.0.0", Some(29596)),
116 (active, log_syntax, "1.0.0", Some(29598)),
117 (active, non_ascii_idents, "1.0.0", Some(28979)),
118 (active, plugin_registrar, "1.0.0", Some(29597)),
119 (active, thread_local, "1.0.0", Some(29594)),
120 (active, trace_macros, "1.0.0", Some(29598)),
122 // rustc internal, for now:
123 (active, intrinsics, "1.0.0", None),
124 (active, lang_items, "1.0.0", None),
126 (active, link_llvm_intrinsics, "1.0.0", Some(29602)),
127 (active, linkage, "1.0.0", Some(29603)),
128 (active, quote, "1.0.0", Some(29601)),
129 (active, simd, "1.0.0", Some(27731)),
133 (active, rustc_diagnostic_macros, "1.0.0", None),
134 (active, advanced_slice_patterns, "1.0.0", Some(23121)),
135 (active, box_syntax, "1.0.0", Some(27779)),
136 (active, placement_in_syntax, "1.0.0", Some(27779)),
137 (active, unboxed_closures, "1.0.0", Some(29625)),
139 (active, allocator, "1.0.0", Some(27389)),
140 (active, fundamental, "1.0.0", Some(29635)),
141 (active, main, "1.0.0", Some(29634)),
142 (active, needs_allocator, "1.4.0", Some(27389)),
143 (active, on_unimplemented, "1.0.0", Some(29628)),
144 (active, plugin, "1.0.0", Some(29597)),
145 (active, simd_ffi, "1.0.0", Some(27731)),
146 (active, start, "1.0.0", Some(29633)),
147 (active, structural_match, "1.8.0", Some(31434)),
148 (active, panic_runtime, "1.10.0", Some(32837)),
149 (active, needs_panic_runtime, "1.10.0", Some(32837)),
151 // OIBIT specific features
152 (active, optin_builtin_traits, "1.0.0", Some(13231)),
154 // macro reexport needs more discussion and stabilization
155 (active, macro_reexport, "1.0.0", Some(29638)),
157 // Allows use of #[staged_api]
159 (active, staged_api, "1.0.0", None),
161 // Allows using #![no_core]
162 (active, no_core, "1.3.0", Some(29639)),
164 // Allows using `box` in patterns; RFC 469
165 (active, box_patterns, "1.0.0", Some(29641)),
167 // Allows using the unsafe_destructor_blind_to_params attribute;
169 (active, dropck_parametricity, "1.3.0", Some(28498)),
171 // Allows using the may_dangle attribute; RFC 1327
172 (active, dropck_eyepatch, "1.10.0", Some(34761)),
174 // Allows the use of custom attributes; RFC 572
175 (active, custom_attribute, "1.0.0", Some(29642)),
177 // Allows the use of #[derive(Anything)] as sugar for
178 // #[derive_Anything].
179 (active, custom_derive, "1.0.0", Some(29644)),
181 // Allows the use of rustc_* attributes; RFC 572
182 (active, rustc_attrs, "1.0.0", Some(29642)),
184 // Allows the use of #[allow_internal_unstable]. This is an
185 // attribute on macro_rules! and can't use the attribute handling
186 // below (it has to be checked before expansion possibly makes
187 // macros disappear).
190 (active, allow_internal_unstable, "1.0.0", None),
192 // #23121. Array patterns have some hazards yet.
193 (active, slice_patterns, "1.0.0", Some(23121)),
195 // Allows the definition of associated constants in `trait` or `impl`
197 (active, associated_consts, "1.0.0", Some(29646)),
199 // Allows the definition of `const fn` functions.
200 (active, const_fn, "1.2.0", Some(24111)),
202 // Allows indexing into constant arrays.
203 (active, const_indexing, "1.4.0", Some(29947)),
205 // Allows using #[prelude_import] on glob `use` items.
208 (active, prelude_import, "1.2.0", None),
210 // Allows default type parameters to influence type inference.
211 (active, default_type_parameter_fallback, "1.3.0", Some(27336)),
213 // Allows associated type defaults
214 (active, associated_type_defaults, "1.2.0", Some(29661)),
216 // allow `repr(simd)`, and importing the various simd intrinsics
217 (active, repr_simd, "1.4.0", Some(27731)),
219 // Allows cfg(target_feature = "...").
220 (active, cfg_target_feature, "1.4.0", Some(29717)),
222 // allow `extern "platform-intrinsic" { ... }`
223 (active, platform_intrinsics, "1.4.0", Some(27731)),
226 // rust runtime internal
227 (active, unwind_attributes, "1.4.0", None),
229 // allow the use of `#[naked]` on functions.
230 (active, naked_functions, "1.9.0", Some(32408)),
232 // allow `#[no_debug]`
233 (active, no_debug, "1.5.0", Some(29721)),
235 // allow `#[omit_gdb_pretty_printer_section]`
237 (active, omit_gdb_pretty_printer_section, "1.5.0", None),
239 // Allows cfg(target_vendor = "...").
240 (active, cfg_target_vendor, "1.5.0", Some(29718)),
242 // Allow attributes on expressions and non-item statements
243 (active, stmt_expr_attributes, "1.6.0", Some(15701)),
245 // allow using type ascription in expressions
246 (active, type_ascription, "1.6.0", Some(23416)),
248 // Allows cfg(target_thread_local)
249 (active, cfg_target_thread_local, "1.7.0", Some(29594)),
252 (active, abi_vectorcall, "1.7.0", None),
255 (active, inclusive_range_syntax, "1.7.0", Some(28237)),
258 (active, exclusive_range_pattern, "1.11.0", Some(37854)),
260 // impl specialization (RFC 1210)
261 (active, specialization, "1.7.0", Some(31844)),
263 // Allow Drop types in statics/const functions (RFC 1440)
264 (active, drop_types_in_const, "1.9.0", Some(33156)),
266 // Allows cfg(target_has_atomic = "...").
267 (active, cfg_target_has_atomic, "1.9.0", Some(32976)),
269 // Allows `impl Trait` in function return types.
270 (active, conservative_impl_trait, "1.12.0", Some(34511)),
272 // Permits numeric fields in struct expressions and patterns.
273 (active, relaxed_adts, "1.12.0", Some(35626)),
276 (active, never_type, "1.13.0", Some(35121)),
278 // Allows all literals in attribute lists and values of key-value pairs.
279 (active, attr_literals, "1.13.0", Some(34981)),
281 // Allows the sysV64 ABI to be specified on all platforms
282 // instead of just the platforms on which it is the C ABI
283 (active, abi_sysv64, "1.13.0", Some(36167)),
285 // Allows untagged unions `union U { ... }`
286 (active, untagged_unions, "1.13.0", Some(32836)),
288 // Used to identify the `compiler_builtins` crate
290 (active, compiler_builtins, "1.13.0", None),
292 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
293 (active, generic_param_attrs, "1.11.0", Some(34761)),
295 // The #![windows_subsystem] attribute
296 (active, windows_subsystem, "1.14.0", Some(37499)),
298 // Allows #[link(..., cfg(..))]
299 (active, link_cfg, "1.14.0", Some(37406)),
301 (active, use_extern_macros, "1.15.0", Some(35896)),
303 // Allows `break {expr}` with a value inside `loop`s.
304 (active, loop_break_value, "1.14.0", Some(37339)),
306 // Allows #[target_feature(...)]
307 (active, target_feature, "1.15.0", None),
309 // `extern "ptx-*" fn()`
310 (active, abi_ptx, "1.15.0", None),
313 (active, i128_type, "1.16.0", Some(35118)),
315 // The `unadjusted` ABI. Perma unstable.
316 (active, abi_unadjusted, "1.16.0", None),
319 (active, proc_macro, "1.16.0", Some(38356)),
321 // Allows attributes on struct literal fields.
322 (active, struct_field_attributes, "1.16.0", Some(38814)),
324 // Allows #[link(kind="static-nobundle"...]
325 (active, static_nobundle, "1.16.0", Some(37403)),
327 // `extern "msp430-interrupt" fn()`
328 (active, abi_msp430_interrupt, "1.16.0", Some(38487)),
330 // Coerces non capturing closures to function pointers
331 (active, closure_to_fn_coercion, "1.17.0", Some(39817)),
333 // Used to identify crates that contain sanitizer runtimes
335 (active, sanitizer_runtime, "1.17.0", None),
337 // `extern "x86-interrupt" fn()`
338 (active, abi_x86_interrupt, "1.17.0", Some(40180)),
340 // Allows the `catch {...}` expression
341 (active, catch_expr, "1.17.0", Some(31436)),
343 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
344 (active, rvalue_static_promotion, "1.15.1", Some(38865)),
348 (removed, import_shadowing, "1.0.0", None),
349 (removed, managed_boxes, "1.0.0", None),
350 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
351 (removed, negate_unsigned, "1.0.0", Some(29645)),
352 (removed, reflect, "1.0.0", Some(27749)),
353 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
354 (removed, opt_out_copy, "1.0.0", None),
355 (removed, quad_precision_float, "1.0.0", None),
356 (removed, struct_inherit, "1.0.0", None),
357 (removed, test_removed_feature, "1.0.0", None),
358 (removed, visible_private_types, "1.0.0", None),
359 (removed, unsafe_no_drop_flag, "1.0.0", None),
360 // Allows using items which are missing stability attributes
362 (removed, unmarked_api, "1.0.0", None),
363 (removed, pushpop_unsafe, "1.2.0", None),
367 (stable_removed, no_stack_check, "1.0.0", None),
371 (accepted, associated_types, "1.0.0", None),
372 // allow overloading augmented assignment operations like `a += b`
373 (accepted, augmented_assignments, "1.8.0", Some(28235)),
374 // allow empty structs and enum variants with braces
375 (accepted, braced_empty_structs, "1.8.0", Some(29720)),
376 (accepted, default_type_params, "1.0.0", None),
377 (accepted, globs, "1.0.0", None),
378 (accepted, if_let, "1.0.0", None),
379 // A temporary feature gate used to enable parser extensions needed
380 // to bootstrap fix for #5723.
381 (accepted, issue_5723_bootstrap, "1.0.0", None),
382 (accepted, macro_rules, "1.0.0", None),
383 // Allows using #![no_std]
384 (accepted, no_std, "1.6.0", None),
385 (accepted, slicing_syntax, "1.0.0", None),
386 (accepted, struct_variant, "1.0.0", None),
387 // These are used to test this portion of the compiler, they don't actually
389 (accepted, test_accepted_feature, "1.0.0", None),
390 (accepted, tuple_indexing, "1.0.0", None),
391 // Allows macros to appear in the type position.
392 (accepted, type_macros, "1.13.0", Some(27245)),
393 (accepted, while_let, "1.0.0", None),
394 // Allows `#[deprecated]` attribute
395 (accepted, deprecated, "1.9.0", Some(29935)),
397 (accepted, question_mark, "1.13.0", Some(31436)),
398 // Allows `..` in tuple (struct) patterns
399 (accepted, dotdot_in_tuple_patterns, "1.14.0", Some(33627)),
400 (accepted, item_like_imports, "1.14.0", Some(35120)),
401 // Allows using `Self` and associated types in struct expressions and patterns.
402 (accepted, more_struct_aliases, "1.16.0", Some(37544)),
403 // elide `'static` lifetimes in `static`s and `const`s
404 (accepted, static_in_const, "1.17.0", Some(35897)),
405 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
406 (accepted, field_init_shorthand, "1.17.0", Some(37340)),
407 // Allows the definition recursive static items.
408 (accepted, static_recursion, "1.17.0", Some(29719)),
409 // pub(restricted) visibilities (RFC 1422)
410 (accepted, pub_restricted, "1.17.0", Some(32409)),
413 // If you change this, please modify src/doc/unstable-book as well. You must
414 // move that documentation into the relevant place in the other docs, and
415 // remove the chapter on the flag.
417 #[derive(PartialEq, Copy, Clone, Debug)]
418 pub enum AttributeType {
419 /// Normal, builtin attribute that is consumed
420 /// by the compiler before the unused_attribute check
423 /// Builtin attribute that may not be consumed by the compiler
424 /// before the unused_attribute check. These attributes
425 /// will be ignored by the unused_attribute lint
428 /// Builtin attribute that is only allowed at the crate level
432 pub enum AttributeGate {
433 /// Is gated by a given feature gate, reason
434 /// and function to check if enabled
435 Gated(Stability, &'static str, &'static str, fn(&Features) -> bool),
437 /// Ungated attribute, can be used on all release channels
442 fn is_deprecated(&self) -> bool {
444 Gated(Stability::Deprecated(_), ..) => true,
450 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
453 // Argument is tracking issue link.
454 Deprecated(&'static str),
458 impl ::std::fmt::Debug for AttributeGate {
459 fn fmt(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
461 Gated(ref stab, ref name, ref expl, _) =>
462 write!(fmt, "Gated({:?}, {}, {})", stab, name, expl),
463 Ungated => write!(fmt, "Ungated")
468 macro_rules! cfg_fn {
469 ($field: ident) => {{
470 fn f(features: &Features) -> bool {
473 f as fn(&Features) -> bool
477 pub fn deprecated_attributes() -> Vec<&'static (&'static str, AttributeType, AttributeGate)> {
478 BUILTIN_ATTRIBUTES.iter().filter(|a| a.2.is_deprecated()).collect()
481 pub fn is_builtin_attr(attr: &ast::Attribute) -> bool {
482 BUILTIN_ATTRIBUTES.iter().any(|&(builtin_name, _, _)| attr.check_name(builtin_name))
485 // Attributes that have a special meaning to rustc or rustdoc
486 pub const BUILTIN_ATTRIBUTES: &'static [(&'static str, AttributeType, AttributeGate)] = &[
489 ("warn", Normal, Ungated),
490 ("allow", Normal, Ungated),
491 ("forbid", Normal, Ungated),
492 ("deny", Normal, Ungated),
494 ("macro_reexport", Normal, Ungated),
495 ("macro_use", Normal, Ungated),
496 ("macro_export", Normal, Ungated),
497 ("plugin_registrar", Normal, Ungated),
499 ("cfg", Normal, Ungated),
500 ("cfg_attr", Normal, Ungated),
501 ("main", Normal, Ungated),
502 ("start", Normal, Ungated),
503 ("test", Normal, Ungated),
504 ("bench", Normal, Ungated),
505 ("simd", Normal, Ungated),
506 ("repr", Normal, Ungated),
507 ("path", Normal, Ungated),
508 ("abi", Normal, Ungated),
509 ("automatically_derived", Normal, Ungated),
510 ("no_mangle", Normal, Ungated),
511 ("no_link", Normal, Ungated),
512 ("derive", Normal, Ungated),
513 ("should_panic", Normal, Ungated),
514 ("ignore", Normal, Ungated),
515 ("no_implicit_prelude", Normal, Ungated),
516 ("reexport_test_harness_main", Normal, Ungated),
517 ("link_args", Normal, Ungated),
518 ("macro_escape", Normal, Ungated),
521 ("structural_match", Whitelisted, Gated(Stability::Unstable,
523 "the semantics of constant patterns is \
525 cfg_fn!(structural_match))),
527 ("plugin", CrateLevel, Gated(Stability::Unstable,
529 "compiler plugins are experimental \
533 ("no_std", CrateLevel, Ungated),
534 ("no_core", CrateLevel, Gated(Stability::Unstable,
536 "no_core is experimental",
538 ("lang", Normal, Gated(Stability::Unstable,
540 "language items are subject to change",
541 cfg_fn!(lang_items))),
542 ("linkage", Whitelisted, Gated(Stability::Unstable,
544 "the `linkage` attribute is experimental \
545 and not portable across platforms",
547 ("thread_local", Whitelisted, Gated(Stability::Unstable,
549 "`#[thread_local]` is an experimental feature, and does \
550 not currently handle destructors. There is no \
551 corresponding `#[task_local]` mapping to the task \
553 cfg_fn!(thread_local))),
555 ("rustc_on_unimplemented", Normal, Gated(Stability::Unstable,
557 "the `#[rustc_on_unimplemented]` attribute \
558 is an experimental feature",
559 cfg_fn!(on_unimplemented))),
560 ("allocator", Whitelisted, Gated(Stability::Unstable,
562 "the `#[allocator]` attribute is an experimental feature",
563 cfg_fn!(allocator))),
564 ("needs_allocator", Normal, Gated(Stability::Unstable,
566 "the `#[needs_allocator]` \
567 attribute is an experimental \
569 cfg_fn!(needs_allocator))),
570 ("panic_runtime", Whitelisted, Gated(Stability::Unstable,
572 "the `#[panic_runtime]` attribute is \
573 an experimental feature",
574 cfg_fn!(panic_runtime))),
575 ("needs_panic_runtime", Whitelisted, Gated(Stability::Unstable,
576 "needs_panic_runtime",
577 "the `#[needs_panic_runtime]` \
578 attribute is an experimental \
580 cfg_fn!(needs_panic_runtime))),
581 ("rustc_variance", Normal, Gated(Stability::Unstable,
583 "the `#[rustc_variance]` attribute \
584 is just used for rustc unit tests \
585 and will never be stable",
586 cfg_fn!(rustc_attrs))),
587 ("rustc_error", Whitelisted, Gated(Stability::Unstable,
589 "the `#[rustc_error]` attribute \
590 is just used for rustc unit tests \
591 and will never be stable",
592 cfg_fn!(rustc_attrs))),
593 ("rustc_if_this_changed", Whitelisted, Gated(Stability::Unstable,
595 "the `#[rustc_if_this_changed]` attribute \
596 is just used for rustc unit tests \
597 and will never be stable",
598 cfg_fn!(rustc_attrs))),
599 ("rustc_then_this_would_need", Whitelisted, Gated(Stability::Unstable,
601 "the `#[rustc_if_this_changed]` attribute \
602 is just used for rustc unit tests \
603 and will never be stable",
604 cfg_fn!(rustc_attrs))),
605 ("rustc_dirty", Whitelisted, Gated(Stability::Unstable,
607 "the `#[rustc_dirty]` attribute \
608 is just used for rustc unit tests \
609 and will never be stable",
610 cfg_fn!(rustc_attrs))),
611 ("rustc_clean", Whitelisted, Gated(Stability::Unstable,
613 "the `#[rustc_clean]` attribute \
614 is just used for rustc unit tests \
615 and will never be stable",
616 cfg_fn!(rustc_attrs))),
617 ("rustc_metadata_dirty", Whitelisted, Gated(Stability::Unstable,
619 "the `#[rustc_metadata_dirty]` attribute \
620 is just used for rustc unit tests \
621 and will never be stable",
622 cfg_fn!(rustc_attrs))),
623 ("rustc_metadata_clean", Whitelisted, Gated(Stability::Unstable,
625 "the `#[rustc_metadata_clean]` attribute \
626 is just used for rustc unit tests \
627 and will never be stable",
628 cfg_fn!(rustc_attrs))),
629 ("rustc_partition_reused", Whitelisted, Gated(Stability::Unstable,
632 is just used for rustc unit tests \
633 and will never be stable",
634 cfg_fn!(rustc_attrs))),
635 ("rustc_partition_translated", Whitelisted, Gated(Stability::Unstable,
638 is just used for rustc unit tests \
639 and will never be stable",
640 cfg_fn!(rustc_attrs))),
641 ("rustc_symbol_name", Whitelisted, Gated(Stability::Unstable,
643 "internal rustc attributes will never be stable",
644 cfg_fn!(rustc_attrs))),
645 ("rustc_item_path", Whitelisted, Gated(Stability::Unstable,
647 "internal rustc attributes will never be stable",
648 cfg_fn!(rustc_attrs))),
649 ("rustc_move_fragments", Normal, Gated(Stability::Unstable,
651 "the `#[rustc_move_fragments]` attribute \
652 is just used for rustc unit tests \
653 and will never be stable",
654 cfg_fn!(rustc_attrs))),
655 ("rustc_mir", Whitelisted, Gated(Stability::Unstable,
657 "the `#[rustc_mir]` attribute \
658 is just used for rustc unit tests \
659 and will never be stable",
660 cfg_fn!(rustc_attrs))),
661 ("rustc_inherit_overflow_checks", Whitelisted, Gated(Stability::Unstable,
663 "the `#[rustc_inherit_overflow_checks]` \
664 attribute is just used to control \
665 overflow checking behavior of several \
666 libcore functions that are inlined \
667 across crates and will never be stable",
668 cfg_fn!(rustc_attrs))),
669 ("compiler_builtins", Whitelisted, Gated(Stability::Unstable,
671 "the `#[compiler_builtins]` attribute is used to \
672 identify the `compiler_builtins` crate which \
673 contains compiler-rt intrinsics and will never be \
675 cfg_fn!(compiler_builtins))),
676 ("sanitizer_runtime", Whitelisted, Gated(Stability::Unstable,
678 "the `#[sanitizer_runtime]` attribute is used to \
679 identify crates that contain the runtime of a \
680 sanitizer and will never be stable",
681 cfg_fn!(sanitizer_runtime))),
683 ("allow_internal_unstable", Normal, Gated(Stability::Unstable,
684 "allow_internal_unstable",
685 EXPLAIN_ALLOW_INTERNAL_UNSTABLE,
686 cfg_fn!(allow_internal_unstable))),
688 ("fundamental", Whitelisted, Gated(Stability::Unstable,
690 "the `#[fundamental]` attribute \
691 is an experimental feature",
692 cfg_fn!(fundamental))),
694 ("proc_macro_derive", Normal, Ungated),
696 ("rustc_copy_clone_marker", Whitelisted, Gated(Stability::Unstable,
698 "internal implementation detail",
699 cfg_fn!(rustc_attrs))),
701 // FIXME: #14408 whitelist docs since rustdoc looks at them
702 ("doc", Whitelisted, Ungated),
704 // FIXME: #14406 these are processed in trans, which happens after the
706 ("cold", Whitelisted, Ungated),
707 ("naked", Whitelisted, Gated(Stability::Unstable,
709 "the `#[naked]` attribute \
710 is an experimental feature",
711 cfg_fn!(naked_functions))),
712 ("target_feature", Whitelisted, Gated(
713 Stability::Unstable, "target_feature",
714 "the `#[target_feature]` attribute is an experimental feature",
715 cfg_fn!(target_feature))),
716 ("export_name", Whitelisted, Ungated),
717 ("inline", Whitelisted, Ungated),
718 ("link", Whitelisted, Ungated),
719 ("link_name", Whitelisted, Ungated),
720 ("link_section", Whitelisted, Ungated),
721 ("no_builtins", Whitelisted, Ungated),
722 ("no_mangle", Whitelisted, Ungated),
723 ("no_debug", Whitelisted, Gated(
724 Stability::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
726 "the `#[no_debug]` attribute is an experimental feature",
728 ("omit_gdb_pretty_printer_section", Whitelisted, Gated(Stability::Unstable,
729 "omit_gdb_pretty_printer_section",
730 "the `#[omit_gdb_pretty_printer_section]` \
731 attribute is just used for the Rust test \
733 cfg_fn!(omit_gdb_pretty_printer_section))),
734 ("unsafe_destructor_blind_to_params",
736 Gated(Stability::Deprecated("https://github.com/rust-lang/rust/issues/34761"),
737 "dropck_parametricity",
738 "unsafe_destructor_blind_to_params has been replaced by \
739 may_dangle and will be removed in the future",
740 cfg_fn!(dropck_parametricity))),
743 Gated(Stability::Unstable,
745 "may_dangle has unstable semantics and may be removed in the future",
746 cfg_fn!(dropck_eyepatch))),
747 ("unwind", Whitelisted, Gated(Stability::Unstable,
749 "#[unwind] is experimental",
750 cfg_fn!(unwind_attributes))),
753 ("prelude_import", Whitelisted, Gated(Stability::Unstable,
755 "`#[prelude_import]` is for use by rustc only",
756 cfg_fn!(prelude_import))),
758 // FIXME: #14407 these are only looked at on-demand so we can't
759 // guarantee they'll have already been checked
760 ("rustc_deprecated", Whitelisted, Ungated),
761 ("must_use", Whitelisted, Ungated),
762 ("stable", Whitelisted, Ungated),
763 ("unstable", Whitelisted, Ungated),
764 ("deprecated", Normal, Ungated),
766 ("rustc_paren_sugar", Normal, Gated(Stability::Unstable,
768 "unboxed_closures are still evolving",
769 cfg_fn!(unboxed_closures))),
771 ("windows_subsystem", Whitelisted, Gated(Stability::Unstable,
773 "the windows subsystem attribute \
774 is currently unstable",
775 cfg_fn!(windows_subsystem))),
777 ("proc_macro_attribute", Normal, Gated(Stability::Unstable,
779 "attribute proc macros are currently unstable",
780 cfg_fn!(proc_macro))),
782 ("proc_macro", Normal, Gated(Stability::Unstable,
784 "function-like proc macros are currently unstable",
785 cfg_fn!(proc_macro))),
787 ("rustc_derive_registrar", Normal, Gated(Stability::Unstable,
788 "rustc_derive_registrar",
789 "used internally by rustc",
790 cfg_fn!(rustc_attrs))),
792 // Crate level attributes
793 ("crate_name", CrateLevel, Ungated),
794 ("crate_type", CrateLevel, Ungated),
795 ("crate_id", CrateLevel, Ungated),
796 ("feature", CrateLevel, Ungated),
797 ("no_start", CrateLevel, Ungated),
798 ("no_main", CrateLevel, Ungated),
799 ("no_builtins", CrateLevel, Ungated),
800 ("recursion_limit", CrateLevel, Ungated),
801 ("type_length_limit", CrateLevel, Ungated),
804 // cfg(...)'s that are feature gated
805 const GATED_CFGS: &'static [(&'static str, &'static str, fn(&Features) -> bool)] = &[
806 // (name in cfg, feature, function to check if the feature is enabled)
807 ("target_feature", "cfg_target_feature", cfg_fn!(cfg_target_feature)),
808 ("target_vendor", "cfg_target_vendor", cfg_fn!(cfg_target_vendor)),
809 ("target_thread_local", "cfg_target_thread_local", cfg_fn!(cfg_target_thread_local)),
810 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn!(cfg_target_has_atomic)),
813 #[derive(Debug, Eq, PartialEq)]
814 pub struct GatedCfg {
820 pub fn gate(cfg: &ast::MetaItem) -> Option<GatedCfg> {
821 let name = cfg.name().as_str();
823 .position(|info| info.0 == name)
832 pub fn check_and_emit(&self, sess: &ParseSess, features: &Features) {
833 let (cfg, feature, has_feature) = GATED_CFGS[self.index];
834 if !has_feature(features) && !self.span.allows_unstable() {
835 let explain = format!("`cfg({})` is experimental and subject to change", cfg);
836 emit_feature_err(sess, feature, self.span, GateIssue::Language, &explain);
842 features: &'a Features,
843 parse_sess: &'a ParseSess,
844 plugin_attributes: &'a [(String, AttributeType)],
847 macro_rules! gate_feature_fn {
848 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
849 let (cx, has_feature, span, name, explain) = ($cx, $has_feature, $span, $name, $explain);
850 let has_feature: bool = has_feature(&$cx.features);
851 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
852 if !has_feature && !span.allows_unstable() {
853 emit_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain);
858 macro_rules! gate_feature {
859 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
860 gate_feature_fn!($cx, |x:&Features| x.$feature, $span, stringify!($feature), $explain)
864 impl<'a> Context<'a> {
865 fn check_attribute(&self, attr: &ast::Attribute, is_macro: bool) {
866 debug!("check_attribute(attr = {:?})", attr);
867 let name = unwrap_or!(attr.name(), return).as_str();
868 for &(n, ty, ref gateage) in BUILTIN_ATTRIBUTES {
870 if let &Gated(_, ref name, ref desc, ref has_feature) = gateage {
871 gate_feature_fn!(self, has_feature, attr.span, name, desc);
873 debug!("check_attribute: {:?} is builtin, {:?}, {:?}", attr.path, ty, gateage);
877 for &(ref n, ref ty) in self.plugin_attributes {
878 if attr.path == &**n {
879 // Plugins can't gate attributes, so we don't check for it
880 // unlike the code above; we only use this loop to
881 // short-circuit to avoid the checks below
882 debug!("check_attribute: {:?} is registered by a plugin, {:?}", attr.path, ty);
886 if name.starts_with("rustc_") {
887 gate_feature!(self, rustc_attrs, attr.span,
888 "unless otherwise specified, attributes \
889 with the prefix `rustc_` \
890 are reserved for internal compiler diagnostics");
891 } else if name.starts_with("derive_") {
892 gate_feature!(self, custom_derive, attr.span, EXPLAIN_DERIVE_UNDERSCORE);
893 } else if !attr::is_known(attr) {
894 // Only run the custom attribute lint during regular
895 // feature gate checking. Macro gating runs
896 // before the plugin attributes are registered
897 // so we skip this then
899 gate_feature!(self, custom_attribute, attr.span,
900 &format!("The attribute `{}` is currently \
901 unknown to the compiler and \
903 added to it in the future",
910 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
911 let cx = Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] };
912 cx.check_attribute(attr, true);
915 pub fn find_lang_feature_accepted_version(feature: &str) -> Option<&'static str> {
916 ACCEPTED_FEATURES.iter().find(|t| t.0 == feature).map(|t| t.1)
919 fn find_lang_feature_issue(feature: &str) -> Option<u32> {
920 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.0 == feature) {
922 // FIXME (#28244): enforce that active features have issue numbers
923 // assert!(issue.is_some())
926 // search in Accepted, Removed, or Stable Removed features
927 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
928 .find(|t| t.0 == feature);
930 Some(&(_, _, issue)) => issue,
931 None => panic!("Feature `{}` is not declared anywhere", feature),
941 pub fn emit_feature_err(sess: &ParseSess, feature: &str, span: Span, issue: GateIssue,
943 feature_err(sess, feature, span, issue, explain).emit();
946 pub fn feature_err<'a>(sess: &'a ParseSess, feature: &str, span: Span, issue: GateIssue,
947 explain: &str) -> DiagnosticBuilder<'a> {
948 let diag = &sess.span_diagnostic;
950 let issue = match issue {
951 GateIssue::Language => find_lang_feature_issue(feature),
952 GateIssue::Library(lib) => lib,
955 let mut err = if let Some(n) = issue {
956 diag.struct_span_err(span, &format!("{} (see issue #{})", explain, n))
958 diag.struct_span_err(span, explain)
961 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
962 if sess.unstable_features.is_nightly_build() {
963 err.help(&format!("add #![feature({})] to the \
964 crate attributes to enable",
971 const EXPLAIN_BOX_SYNTAX: &'static str =
972 "box expression syntax is experimental; you can call `Box::new` instead.";
974 pub const EXPLAIN_STMT_ATTR_SYNTAX: &'static str =
975 "attributes on non-item statements and expressions are experimental.";
977 pub const EXPLAIN_ASM: &'static str =
978 "inline assembly is not stable enough for use and is subject to change";
980 pub const EXPLAIN_LOG_SYNTAX: &'static str =
981 "`log_syntax!` is not stable enough for use and is subject to change";
983 pub const EXPLAIN_CONCAT_IDENTS: &'static str =
984 "`concat_idents` is not stable enough for use and is subject to change";
986 pub const EXPLAIN_TRACE_MACROS: &'static str =
987 "`trace_macros` is not stable enough for use and is subject to change";
988 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &'static str =
989 "allow_internal_unstable side-steps feature gating and stability checks";
991 pub const EXPLAIN_CUSTOM_DERIVE: &'static str =
992 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
994 pub const EXPLAIN_DEPR_CUSTOM_DERIVE: &'static str =
995 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
996 Prefer using procedural macro custom derive.";
998 pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
999 "attributes of the form `#[derive_*]` are reserved for the compiler";
1001 pub const EXPLAIN_PLACEMENT_IN: &'static str =
1002 "placement-in expression syntax is experimental and subject to change.";
1004 pub const CLOSURE_TO_FN_COERCION: &'static str =
1005 "non-capturing closure to fn coercion is experimental";
1007 struct PostExpansionVisitor<'a> {
1008 context: &'a Context<'a>,
1011 macro_rules! gate_feature_post {
1012 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
1013 let (cx, span) = ($cx, $span);
1014 if !span.allows_unstable() {
1015 gate_feature!(cx.context, $feature, span, $explain)
1020 impl<'a> PostExpansionVisitor<'a> {
1021 fn check_abi(&self, abi: Abi, span: Span) {
1023 Abi::RustIntrinsic => {
1024 gate_feature_post!(&self, intrinsics, span,
1025 "intrinsics are subject to change");
1027 Abi::PlatformIntrinsic => {
1028 gate_feature_post!(&self, platform_intrinsics, span,
1029 "platform intrinsics are experimental and possibly buggy");
1031 Abi::Vectorcall => {
1032 gate_feature_post!(&self, abi_vectorcall, span,
1033 "vectorcall is experimental and subject to change");
1036 gate_feature_post!(&self, unboxed_closures, span,
1037 "rust-call ABI is subject to change");
1040 gate_feature_post!(&self, abi_sysv64, span,
1041 "sysv64 ABI is experimental and subject to change");
1044 gate_feature_post!(&self, abi_ptx, span,
1045 "PTX ABIs are experimental and subject to change");
1047 Abi::Unadjusted => {
1048 gate_feature_post!(&self, abi_unadjusted, span,
1049 "unadjusted ABI is an implementation detail and perma-unstable");
1051 Abi::Msp430Interrupt => {
1052 gate_feature_post!(&self, abi_msp430_interrupt, span,
1053 "msp430-interrupt ABI is experimental and subject to change");
1055 Abi::X86Interrupt => {
1056 gate_feature_post!(&self, abi_x86_interrupt, span,
1057 "x86-interrupt ABI is experimental and subject to change");
1072 fn contains_novel_literal(item: &ast::MetaItem) -> bool {
1073 use ast::MetaItemKind::*;
1074 use ast::NestedMetaItemKind::*;
1078 NameValue(ref lit) => !lit.node.is_str(),
1079 List(ref list) => list.iter().any(|li| {
1081 MetaItem(ref mi) => contains_novel_literal(&mi),
1088 fn starts_with_digit(s: &str) -> bool {
1089 s.as_bytes().first().cloned().map_or(false, |b| b >= b'0' && b <= b'9')
1092 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
1093 fn visit_attribute(&mut self, attr: &ast::Attribute) {
1094 if !attr.span.allows_unstable() {
1095 // check for gated attributes
1096 self.context.check_attribute(attr, false);
1099 if self.context.features.proc_macro && attr::is_known(attr) {
1103 let meta = panictry!(attr.parse_meta(&self.context.parse_sess));
1104 if contains_novel_literal(&meta) {
1105 gate_feature_post!(&self, attr_literals, attr.span,
1106 "non-string literals in attributes, or string \
1107 literals in top-level positions, are experimental");
1111 fn visit_name(&mut self, sp: Span, name: ast::Name) {
1112 if !name.as_str().is_ascii() {
1113 gate_feature_post!(&self, non_ascii_idents, sp,
1114 "non-ascii idents are not fully supported.");
1118 fn visit_item(&mut self, i: &'a ast::Item) {
1120 ast::ItemKind::ExternCrate(_) => {
1121 if attr::contains_name(&i.attrs[..], "macro_reexport") {
1122 gate_feature_post!(&self, macro_reexport, i.span,
1123 "macros reexports are experimental \
1124 and possibly buggy");
1128 ast::ItemKind::ForeignMod(ref foreign_module) => {
1129 if attr::contains_name(&i.attrs[..], "link_args") {
1130 gate_feature_post!(&self, link_args, i.span,
1131 "the `link_args` attribute is not portable \
1132 across platforms, it is recommended to \
1133 use `#[link(name = \"foo\")]` instead")
1135 self.check_abi(foreign_module.abi, i.span);
1138 ast::ItemKind::Fn(..) => {
1139 if attr::contains_name(&i.attrs[..], "plugin_registrar") {
1140 gate_feature_post!(&self, plugin_registrar, i.span,
1141 "compiler plugins are experimental and possibly buggy");
1143 if attr::contains_name(&i.attrs[..], "start") {
1144 gate_feature_post!(&self, start, i.span,
1145 "a #[start] function is an experimental \
1146 feature whose signature may change \
1149 if attr::contains_name(&i.attrs[..], "main") {
1150 gate_feature_post!(&self, main, i.span,
1151 "declaration of a nonstandard #[main] \
1152 function may change over time, for now \
1153 a top-level `fn main()` is required");
1157 ast::ItemKind::Struct(..) => {
1158 if attr::contains_name(&i.attrs[..], "simd") {
1159 gate_feature_post!(&self, simd, i.span,
1160 "SIMD types are experimental and possibly buggy");
1161 self.context.parse_sess.span_diagnostic.span_warn(i.span,
1162 "the `#[simd]` attribute \
1163 is deprecated, use \
1164 `#[repr(simd)]` instead");
1166 for attr in &i.attrs {
1167 if attr.path == "repr" {
1168 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
1169 if item.check_name("simd") {
1170 gate_feature_post!(&self, repr_simd, i.span,
1171 "SIMD types are experimental \
1172 and possibly buggy");
1180 ast::ItemKind::Union(..) => {
1181 gate_feature_post!(&self, untagged_unions,
1183 "unions are unstable and possibly buggy");
1186 ast::ItemKind::DefaultImpl(..) => {
1187 gate_feature_post!(&self, optin_builtin_traits,
1189 "default trait implementations are experimental \
1190 and possibly buggy");
1193 ast::ItemKind::Impl(_, polarity, _, _, _, _) => {
1195 ast::ImplPolarity::Negative => {
1196 gate_feature_post!(&self, optin_builtin_traits,
1198 "negative trait bounds are not yet fully implemented; \
1199 use marker types for now");
1208 visit::walk_item(self, i);
1211 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
1212 let links_to_llvm = match attr::first_attr_value_str_by_name(&i.attrs, "link_name") {
1213 Some(val) => val.as_str().starts_with("llvm."),
1217 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
1218 "linking to LLVM intrinsics is experimental");
1221 visit::walk_foreign_item(self, i)
1224 fn visit_ty(&mut self, ty: &'a ast::Ty) {
1226 ast::TyKind::BareFn(ref bare_fn_ty) => {
1227 self.check_abi(bare_fn_ty.abi, ty.span);
1229 ast::TyKind::ImplTrait(..) => {
1230 gate_feature_post!(&self, conservative_impl_trait, ty.span,
1231 "`impl Trait` is experimental");
1233 ast::TyKind::Never => {
1234 gate_feature_post!(&self, never_type, ty.span,
1235 "The `!` type is experimental");
1239 visit::walk_ty(self, ty)
1242 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
1243 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
1244 match output_ty.node {
1245 ast::TyKind::Never => return,
1248 self.visit_ty(output_ty)
1252 fn visit_expr(&mut self, e: &'a ast::Expr) {
1254 ast::ExprKind::Box(_) => {
1255 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
1257 ast::ExprKind::Type(..) => {
1258 gate_feature_post!(&self, type_ascription, e.span,
1259 "type ascription is experimental");
1261 ast::ExprKind::Range(_, _, ast::RangeLimits::Closed) => {
1262 gate_feature_post!(&self, inclusive_range_syntax,
1264 "inclusive range syntax is experimental");
1266 ast::ExprKind::InPlace(..) => {
1267 gate_feature_post!(&self, placement_in_syntax, e.span, EXPLAIN_PLACEMENT_IN);
1269 ast::ExprKind::Struct(_, ref fields, _) => {
1270 for field in fields {
1271 if starts_with_digit(&field.ident.node.name.as_str()) {
1272 gate_feature_post!(&self, relaxed_adts,
1274 "numeric fields in struct expressions are unstable");
1278 ast::ExprKind::Break(_, Some(_)) => {
1279 gate_feature_post!(&self, loop_break_value, e.span,
1280 "`break` with a value is experimental");
1282 ast::ExprKind::Lit(ref lit) => {
1283 if let ast::LitKind::Int(_, ref ty) = lit.node {
1285 ast::LitIntType::Signed(ast::IntTy::I128) |
1286 ast::LitIntType::Unsigned(ast::UintTy::U128) => {
1287 gate_feature_post!(&self, i128_type, e.span,
1288 "128-bit integers are not stable");
1294 ast::ExprKind::Catch(_) => {
1295 gate_feature_post!(&self, catch_expr, e.span, "`catch` expression is experimental");
1299 visit::walk_expr(self, e);
1302 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
1303 match pattern.node {
1304 PatKind::Slice(_, Some(_), ref last) if !last.is_empty() => {
1305 gate_feature_post!(&self, advanced_slice_patterns,
1307 "multiple-element slice matches anywhere \
1308 but at the end of a slice (e.g. \
1309 `[0, ..xs, 0]`) are experimental")
1311 PatKind::Slice(..) => {
1312 gate_feature_post!(&self, slice_patterns,
1314 "slice pattern syntax is experimental");
1316 PatKind::Box(..) => {
1317 gate_feature_post!(&self, box_patterns,
1319 "box pattern syntax is experimental");
1321 PatKind::Struct(_, ref fields, _) => {
1322 for field in fields {
1323 if starts_with_digit(&field.node.ident.name.as_str()) {
1324 gate_feature_post!(&self, relaxed_adts,
1326 "numeric fields in struct patterns are unstable");
1330 PatKind::Range(_, _, RangeEnd::Excluded) => {
1331 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
1332 "exclusive range pattern syntax is experimental");
1336 visit::walk_pat(self, pattern)
1339 fn visit_fn(&mut self,
1340 fn_kind: FnKind<'a>,
1341 fn_decl: &'a ast::FnDecl,
1344 // check for const fn declarations
1346 FnKind::ItemFn(_, _, _, Spanned { node: ast::Constness::Const, .. }, _, _, _) => {
1347 gate_feature_post!(&self, const_fn, span, "const fn is unstable");
1350 // stability of const fn methods are covered in
1351 // visit_trait_item and visit_impl_item below; this is
1352 // because default methods don't pass through this
1358 FnKind::ItemFn(_, _, _, _, abi, _, _) |
1359 FnKind::Method(_, &ast::MethodSig { abi, .. }, _, _) => {
1360 self.check_abi(abi, span);
1364 visit::walk_fn(self, fn_kind, fn_decl, span);
1367 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
1369 ast::TraitItemKind::Const(..) => {
1370 gate_feature_post!(&self, associated_consts,
1372 "associated constants are experimental")
1374 ast::TraitItemKind::Method(ref sig, ref block) => {
1375 if block.is_none() {
1376 self.check_abi(sig.abi, ti.span);
1378 if sig.constness.node == ast::Constness::Const {
1379 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
1382 ast::TraitItemKind::Type(_, Some(_)) => {
1383 gate_feature_post!(&self, associated_type_defaults, ti.span,
1384 "associated type defaults are unstable");
1388 visit::walk_trait_item(self, ti);
1391 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
1392 if ii.defaultness == ast::Defaultness::Default {
1393 gate_feature_post!(&self, specialization,
1395 "specialization is unstable");
1399 ast::ImplItemKind::Const(..) => {
1400 gate_feature_post!(&self, associated_consts,
1402 "associated constants are experimental")
1404 ast::ImplItemKind::Method(ref sig, _) => {
1405 if sig.constness.node == ast::Constness::Const {
1406 gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable");
1411 visit::walk_impl_item(self, ii);
1414 fn visit_generics(&mut self, g: &'a ast::Generics) {
1415 for t in &g.ty_params {
1416 if !t.attrs.is_empty() {
1417 gate_feature_post!(&self, generic_param_attrs, t.attrs[0].span,
1418 "attributes on type parameter bindings are experimental");
1421 visit::walk_generics(self, g)
1424 fn visit_lifetime_def(&mut self, lifetime_def: &'a ast::LifetimeDef) {
1425 if !lifetime_def.attrs.is_empty() {
1426 gate_feature_post!(&self, generic_param_attrs, lifetime_def.attrs[0].span,
1427 "attributes on lifetime bindings are experimental");
1429 visit::walk_lifetime_def(self, lifetime_def)
1433 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute]) -> Features {
1434 let mut features = Features::new();
1436 let mut feature_checker = MutexFeatureChecker::default();
1438 for attr in krate_attrs {
1439 if !attr.check_name("feature") {
1443 match attr.meta_item_list() {
1445 span_err!(span_handler, attr.span, E0555,
1446 "malformed feature attribute, expected #![feature(...)]");
1450 let name = if let Some(word) = mi.word() {
1453 span_err!(span_handler, mi.span, E0556,
1454 "malformed feature, expected just one word");
1458 if let Some(&(_, _, _, setter)) = ACTIVE_FEATURES.iter()
1459 .find(|& &(n, _, _, _)| name == n) {
1460 *(setter(&mut features)) = true;
1461 feature_checker.collect(&features, mi.span);
1463 else if let Some(&(_, _, _)) = REMOVED_FEATURES.iter()
1464 .find(|& &(n, _, _)| name == n)
1465 .or_else(|| STABLE_REMOVED_FEATURES.iter()
1466 .find(|& &(n, _, _)| name == n)) {
1467 span_err!(span_handler, mi.span, E0557, "feature has been removed");
1469 else if let Some(&(_, _, _)) = ACCEPTED_FEATURES.iter()
1470 .find(|& &(n, _, _)| name == n) {
1471 features.declared_stable_lang_features.push((name, mi.span));
1473 features.declared_lib_features.push((name, mi.span));
1480 feature_checker.check(span_handler);
1485 // A collector for mutually-exclusive features and their flag spans
1487 struct MutexFeatureChecker {
1488 proc_macro: Option<Span>,
1489 custom_attribute: Option<Span>,
1492 impl MutexFeatureChecker {
1493 // If this method turns out to be a hotspot due to branching,
1494 // the branching can be eliminated by modifying `setter!()` to set these spans
1495 // only for the features that need to be checked for mutual exclusion.
1496 fn collect(&mut self, features: &Features, span: Span) {
1497 if features.proc_macro {
1498 // If self.proc_macro is None, set to Some(span)
1499 self.proc_macro = self.proc_macro.or(Some(span));
1502 if features.custom_attribute {
1503 self.custom_attribute = self.custom_attribute.or(Some(span));
1507 fn check(self, handler: &Handler) {
1508 if let (Some(pm_span), Some(ca_span)) = (self.proc_macro, self.custom_attribute) {
1509 handler.struct_span_err(pm_span, "Cannot use `#![feature(proc_macro)]` and \
1510 `#![feature(custom_attribute)] at the same time")
1511 .span_note(ca_span, "`#![feature(custom_attribute)]` declared here")
1519 pub fn check_crate(krate: &ast::Crate,
1521 features: &Features,
1522 plugin_attributes: &[(String, AttributeType)],
1523 unstable: UnstableFeatures) {
1524 maybe_stage_features(&sess.span_diagnostic, krate, unstable);
1528 plugin_attributes: plugin_attributes,
1530 visit::walk_crate(&mut PostExpansionVisitor { context: &ctx }, krate);
1533 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
1534 pub enum UnstableFeatures {
1535 /// Hard errors for unstable features are active, as on
1536 /// beta/stable channels.
1538 /// Allow features to be activated, as on nightly.
1540 /// Errors are bypassed for bootstrapping. This is required any time
1541 /// during the build that feature-related lints are set to warn or above
1542 /// because the build turns on warnings-as-errors and uses lots of unstable
1543 /// features. As a result, this is always required for building Rust itself.
1547 impl UnstableFeatures {
1548 pub fn from_environment() -> UnstableFeatures {
1549 // Whether this is a feature-staged build, i.e. on the beta or stable channel
1550 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
1551 // Whether we should enable unstable features for bootstrapping
1552 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
1553 match (disable_unstable_features, bootstrap) {
1554 (_, true) => UnstableFeatures::Cheat,
1555 (true, _) => UnstableFeatures::Disallow,
1556 (false, _) => UnstableFeatures::Allow
1560 pub fn is_nightly_build(&self) -> bool {
1562 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
1568 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate,
1569 unstable: UnstableFeatures) {
1570 let allow_features = match unstable {
1571 UnstableFeatures::Allow => true,
1572 UnstableFeatures::Disallow => false,
1573 UnstableFeatures::Cheat => true
1575 if !allow_features {
1576 for attr in &krate.attrs {
1577 if attr.check_name("feature") {
1578 let release_channel = option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
1579 span_err!(span_handler, attr.span, E0554,
1580 "#[feature] may not be used on the {} release channel",