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, RangeSyntax}
;
33 use errors
::{DiagnosticBuilder, Handler, FatalError}
;
34 use visit
::{self, FnKind, Visitor}
;
36 use symbol
::{keywords, Symbol}
;
42 fn f(features
: &mut Features
, span
: Span
) {
43 features
.declared_lib_features
.push((Symbol
::intern("proc_macro"), span
));
44 features
.proc_macro
= true;
46 f
as fn(&mut Features
, Span
)
49 fn f(features
: &mut Features
, _
: Span
) {
50 features
.$field
= true;
52 f
as fn(&mut Features
, Span
)
56 macro_rules
! declare_features
{
57 ($
((active
, $feature
: ident
, $ver
: expr
, $issue
: expr
),)+) => {
58 /// Represents active features that are currently being implemented or
59 /// currently being considered for addition/removal.
60 const ACTIVE_FEATURES
:
61 &'
static [(&'
static str, &'
static str, Option
<u32>, fn(&mut Features
, Span
))] =
62 &[$
((stringify
!($feature
), $ver
, $issue
, set
!($feature
))),+];
64 /// A set of features to be used by later passes.
66 /// `#![feature]` attrs for stable language features, for error reporting
67 pub declared_stable_lang_features
: Vec
<(Symbol
, Span
)>,
68 /// `#![feature]` attrs for non-language (library) features
69 pub declared_lib_features
: Vec
<(Symbol
, Span
)>,
70 $
(pub $feature
: bool
),+
74 pub fn new() -> Features
{
76 declared_stable_lang_features
: Vec
::new(),
77 declared_lib_features
: Vec
::new(),
84 ($
((removed
, $feature
: ident
, $ver
: expr
, $issue
: expr
),)+) => {
85 /// Represents unstable features which have since been removed (it was once Active)
86 const REMOVED_FEATURES
: &'
static [(&'
static str, &'
static str, Option
<u32>)] = &[
87 $
((stringify
!($feature
), $ver
, $issue
)),+
91 ($
((stable_removed
, $feature
: ident
, $ver
: expr
, $issue
: expr
),)+) => {
92 /// Represents stable features which have since been removed (it was once Accepted)
93 const STABLE_REMOVED_FEATURES
: &'
static [(&'
static str, &'
static str, Option
<u32>)] = &[
94 $
((stringify
!($feature
), $ver
, $issue
)),+
98 ($
((accepted
, $feature
: ident
, $ver
: expr
, $issue
: expr
),)+) => {
99 /// Those language feature has since been Accepted (it was once Active)
100 const ACCEPTED_FEATURES
: &'
static [(&'
static str, &'
static str, Option
<u32>)] = &[
101 $
((stringify
!($feature
), $ver
, $issue
)),+
106 // If you change this, please modify src/doc/unstable-book as well.
108 // Don't ever remove anything from this list; set them to 'Removed'.
110 // The version numbers here correspond to the version in which the current status
111 // was set. This is most important for knowing when a particular feature became
114 // NB: tools/tidy/src/features.rs parses this information directly out of the
115 // source, so take care when modifying it.
118 (active
, asm
, "1.0.0", Some(29722)),
119 (active
, concat_idents
, "1.0.0", Some(29599)),
120 (active
, link_args
, "1.0.0", Some(29596)),
121 (active
, log_syntax
, "1.0.0", Some(29598)),
122 (active
, non_ascii_idents
, "1.0.0", Some(28979)),
123 (active
, plugin_registrar
, "1.0.0", Some(29597)),
124 (active
, thread_local
, "1.0.0", Some(29594)),
125 (active
, trace_macros
, "1.0.0", Some(29598)),
127 // rustc internal, for now:
128 (active
, intrinsics
, "1.0.0", None
),
129 (active
, lang_items
, "1.0.0", None
),
131 (active
, link_llvm_intrinsics
, "1.0.0", Some(29602)),
132 (active
, linkage
, "1.0.0", Some(29603)),
133 (active
, quote
, "1.0.0", Some(29601)),
137 (active
, rustc_diagnostic_macros
, "1.0.0", None
),
138 (active
, rustc_const_unstable
, "1.0.0", None
),
139 (active
, advanced_slice_patterns
, "1.0.0", Some(23121)),
140 (active
, box_syntax
, "1.0.0", Some(27779)),
141 (active
, placement_in_syntax
, "1.0.0", Some(27779)),
142 (active
, unboxed_closures
, "1.0.0", Some(29625)),
144 (active
, fundamental
, "1.0.0", Some(29635)),
145 (active
, main
, "1.0.0", Some(29634)),
146 (active
, needs_allocator
, "1.4.0", Some(27389)),
147 (active
, on_unimplemented
, "1.0.0", Some(29628)),
148 (active
, plugin
, "1.0.0", Some(29597)),
149 (active
, simd_ffi
, "1.0.0", Some(27731)),
150 (active
, start
, "1.0.0", Some(29633)),
151 (active
, structural_match
, "1.8.0", Some(31434)),
152 (active
, panic_runtime
, "1.10.0", Some(32837)),
153 (active
, needs_panic_runtime
, "1.10.0", Some(32837)),
155 // OIBIT specific features
156 (active
, optin_builtin_traits
, "1.0.0", Some(13231)),
158 // macro re-export needs more discussion and stabilization
159 (active
, macro_reexport
, "1.0.0", Some(29638)),
161 // Allows use of #[staged_api]
163 (active
, staged_api
, "1.0.0", None
),
165 // Allows using #![no_core]
166 (active
, no_core
, "1.3.0", Some(29639)),
168 // Allows using `box` in patterns; RFC 469
169 (active
, box_patterns
, "1.0.0", Some(29641)),
171 // Allows using the unsafe_destructor_blind_to_params attribute;
173 (active
, dropck_parametricity
, "1.3.0", Some(28498)),
175 // Allows using the may_dangle attribute; RFC 1327
176 (active
, dropck_eyepatch
, "1.10.0", Some(34761)),
178 // Allows the use of custom attributes; RFC 572
179 (active
, custom_attribute
, "1.0.0", Some(29642)),
181 // Allows the use of #[derive(Anything)] as sugar for
182 // #[derive_Anything].
183 (active
, custom_derive
, "1.0.0", Some(29644)),
185 // Allows the use of rustc_* attributes; RFC 572
186 (active
, rustc_attrs
, "1.0.0", Some(29642)),
188 // Allows the use of non lexical lifetimes; RFC 2094
189 (active
, nll
, "1.0.0", Some(44928)),
191 // Allows the use of #[allow_internal_unstable]. This is an
192 // attribute on macro_rules! and can't use the attribute handling
193 // below (it has to be checked before expansion possibly makes
194 // macros disappear).
197 (active
, allow_internal_unstable
, "1.0.0", None
),
199 // Allows the use of #[allow_internal_unsafe]. This is an
200 // attribute on macro_rules! and can't use the attribute handling
201 // below (it has to be checked before expansion possibly makes
202 // macros disappear).
205 (active
, allow_internal_unsafe
, "1.0.0", None
),
207 // #23121. Array patterns have some hazards yet.
208 (active
, slice_patterns
, "1.0.0", Some(23121)),
210 // Allows the definition of `const fn` functions.
211 (active
, const_fn
, "1.2.0", Some(24111)),
213 // Allows indexing into constant arrays.
214 (active
, const_indexing
, "1.4.0", Some(29947)),
216 // Allows using #[prelude_import] on glob `use` items.
219 (active
, prelude_import
, "1.2.0", None
),
221 // Allows default type parameters to influence type inference.
222 (active
, default_type_parameter_fallback
, "1.3.0", Some(27336)),
224 // Allows associated type defaults
225 (active
, associated_type_defaults
, "1.2.0", Some(29661)),
227 // allow `repr(simd)`, and importing the various simd intrinsics
228 (active
, repr_simd
, "1.4.0", Some(27731)),
230 // Allows cfg(target_feature = "...").
231 (active
, cfg_target_feature
, "1.4.0", Some(29717)),
233 // allow `extern "platform-intrinsic" { ... }`
234 (active
, platform_intrinsics
, "1.4.0", Some(27731)),
237 // rust runtime internal
238 (active
, unwind_attributes
, "1.4.0", None
),
240 // allow the use of `#[naked]` on functions.
241 (active
, naked_functions
, "1.9.0", Some(32408)),
243 // allow `#[no_debug]`
244 (active
, no_debug
, "1.5.0", Some(29721)),
246 // allow `#[omit_gdb_pretty_printer_section]`
248 (active
, omit_gdb_pretty_printer_section
, "1.5.0", None
),
250 // Allows cfg(target_vendor = "...").
251 (active
, cfg_target_vendor
, "1.5.0", Some(29718)),
253 // Allow attributes on expressions and non-item statements
254 (active
, stmt_expr_attributes
, "1.6.0", Some(15701)),
256 // allow using type ascription in expressions
257 (active
, type_ascription
, "1.6.0", Some(23416)),
259 // Allows cfg(target_thread_local)
260 (active
, cfg_target_thread_local
, "1.7.0", Some(29594)),
263 (active
, abi_vectorcall
, "1.7.0", None
),
266 (active
, inclusive_range_syntax
, "1.7.0", Some(28237)),
269 (active
, exclusive_range_pattern
, "1.11.0", Some(37854)),
271 // impl specialization (RFC 1210)
272 (active
, specialization
, "1.7.0", Some(31844)),
274 // Allows cfg(target_has_atomic = "...").
275 (active
, cfg_target_has_atomic
, "1.9.0", Some(32976)),
277 // Allows `impl Trait` in function return types.
278 (active
, conservative_impl_trait
, "1.12.0", Some(34511)),
280 // Allows `impl Trait` in function arguments.
281 (active
, universal_impl_trait
, "1.23.0", Some(34511)),
284 (active
, never_type
, "1.13.0", Some(35121)),
286 // Allows all literals in attribute lists and values of key-value pairs.
287 (active
, attr_literals
, "1.13.0", Some(34981)),
289 // Allows untagged unions `union U { ... }`
290 (active
, untagged_unions
, "1.13.0", Some(32836)),
292 // Used to identify the `compiler_builtins` crate
294 (active
, compiler_builtins
, "1.13.0", None
),
296 // Allows attributes on lifetime/type formal parameters in generics (RFC 1327)
297 (active
, generic_param_attrs
, "1.11.0", Some(34761)),
299 // Allows #[link(..., cfg(..))]
300 (active
, link_cfg
, "1.14.0", Some(37406)),
302 (active
, use_extern_macros
, "1.15.0", Some(35896)),
304 // Allows #[target_feature(...)]
305 (active
, target_feature
, "1.15.0", None
),
307 // `extern "ptx-*" fn()`
308 (active
, abi_ptx
, "1.15.0", None
),
311 (active
, i128_type
, "1.16.0", Some(35118)),
313 // The `repr(i128)` annotation for enums
314 (active
, repr128
, "1.16.0", Some(35118)),
316 // The `unadjusted` ABI. Perma unstable.
317 (active
, abi_unadjusted
, "1.16.0", None
),
319 // Procedural macros 2.0.
320 (active
, proc_macro
, "1.16.0", Some(38356)),
322 // Declarative macros 2.0 (`macro`).
323 (active
, decl_macro
, "1.17.0", Some(39412)),
325 // Allows #[link(kind="static-nobundle"...]
326 (active
, static_nobundle
, "1.16.0", Some(37403)),
328 // `extern "msp430-interrupt" fn()`
329 (active
, abi_msp430_interrupt
, "1.16.0", Some(38487)),
331 // Used to identify crates that contain sanitizer runtimes
333 (active
, sanitizer_runtime
, "1.17.0", None
),
335 // Used to identify crates that contain the profiler runtime
337 (active
, profiler_runtime
, "1.18.0", None
),
339 // `extern "x86-interrupt" fn()`
340 (active
, abi_x86_interrupt
, "1.17.0", Some(40180)),
343 // Allows the `catch {...}` expression
344 (active
, catch_expr
, "1.17.0", Some(31436)),
346 // Used to preserve symbols (see llvm.used)
347 (active
, used
, "1.18.0", Some(40289)),
349 // Allows module-level inline assembly by way of global_asm!()
350 (active
, global_asm
, "1.18.0", Some(35119)),
352 // Allows overlapping impls of marker traits
353 (active
, overlapping_marker_traits
, "1.18.0", Some(29864)),
355 // Allows use of the :vis macro fragment specifier
356 (active
, macro_vis_matcher
, "1.18.0", Some(41022)),
359 (active
, abi_thiscall
, "1.19.0", None
),
361 // Allows a test to fail without failing the whole suite
362 (active
, allow_fail
, "1.19.0", Some(42219)),
364 // Allows unsized tuple coercion.
365 (active
, unsized_tuple_coercion
, "1.20.0", Some(42877)),
368 (active
, generators
, "1.21.0", None
),
371 (active
, trait_alias
, "1.24.0", Some(41517)),
373 // global allocators and their internals
374 (active
, global_allocator
, "1.20.0", None
),
375 (active
, allocator_internals
, "1.20.0", None
),
378 (active
, doc_cfg
, "1.21.0", Some(43781)),
380 (active
, doc_masked
, "1.21.0", Some(44027)),
382 (active
, doc_spotlight
, "1.22.0", Some(45040)),
383 // #[doc(include="some-file")]
384 (active
, external_doc
, "1.22.0", Some(44732)),
386 // allow `#[must_use]` on functions and comparison operators (RFC 1940)
387 (active
, fn_must_use
, "1.21.0", Some(43302)),
389 // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
390 (active
, non_exhaustive
, "1.22.0", Some(44109)),
392 // Copy/Clone closures (RFC 2132)
393 (active
, clone_closures
, "1.22.0", Some(44490)),
394 (active
, copy_closures
, "1.22.0", Some(44490)),
396 // allow `'_` placeholder lifetimes
397 (active
, underscore_lifetimes
, "1.22.0", Some(44524)),
399 // allow `..=` in patterns (RFC 1192)
400 (active
, dotdoteq_in_patterns
, "1.22.0", Some(28237)),
402 // Default match binding modes (RFC 2005)
403 (active
, match_default_bindings
, "1.22.0", Some(42640)),
405 // Trait object syntax with `dyn` prefix
406 (active
, dyn_trait
, "1.22.0", Some(44662)),
408 // `crate` as visibility modifier, synonymous to `pub(crate)`
409 (active
, crate_visibility_modifier
, "1.23.0", Some(45388)),
412 (active
, extern_types
, "1.23.0", Some(43467)),
414 // Allow trait methods with arbitrary self types
415 (active
, arbitrary_self_types
, "1.23.0", Some(44874)),
417 // #![wasm_import_memory] attribute
418 (active
, wasm_import_memory
, "1.22.0", None
),
421 (active
, crate_in_paths
, "1.23.0", Some(45477)),
423 // In-band lifetime bindings (e.g. `fn foo(x: &'a u8) -> &'a u8`)
424 (active
, in_band_lifetimes
, "1.23.0", Some(44524)),
426 // generic associated types (RFC 1598)
427 (active
, generic_associated_types
, "1.23.0", Some(44265)),
429 // Resolve absolute paths as paths from other crates
430 (active
, extern_absolute_paths
, "1.24.0", Some(44660)),
432 // `foo.rs` as an alternative to `foo/mod.rs`
433 (active
, non_modrs_mods
, "1.24.0", Some(44660)),
435 // Nested `impl Trait`
436 (active
, nested_impl_trait
, "1.24.0", Some(34511)),
438 // Termination trait in main (RFC 1937)
439 (active
, termination_trait
, "1.24.0", Some(43301)),
441 // Allows use of the :lifetime macro fragment specifier
442 (active
, macro_lifetime_matcher
, "1.24.0", Some(46895)),
445 (active
, extern_in_paths
, "1.23.0", Some(44660)),
447 // Allows `#[repr(transparent)]` attribute on newtype structs
448 (active
, repr_transparent
, "1.25.0", Some(43036)),
450 // Use `?` as the Kleene "at most one" operator
451 (active
, macro_at_most_once_rep
, "1.25.0", Some(48075)),
455 (removed
, import_shadowing
, "1.0.0", None
),
456 (removed
, managed_boxes
, "1.0.0", None
),
457 // Allows use of unary negate on unsigned integers, e.g. -e for e: u8
458 (removed
, negate_unsigned
, "1.0.0", Some(29645)),
459 (removed
, reflect
, "1.0.0", Some(27749)),
460 // A way to temporarily opt out of opt in copy. This will *never* be accepted.
461 (removed
, opt_out_copy
, "1.0.0", None
),
462 (removed
, quad_precision_float
, "1.0.0", None
),
463 (removed
, struct_inherit
, "1.0.0", None
),
464 (removed
, test_removed_feature
, "1.0.0", None
),
465 (removed
, visible_private_types
, "1.0.0", None
),
466 (removed
, unsafe_no_drop_flag
, "1.0.0", None
),
467 // Allows using items which are missing stability attributes
469 (removed
, unmarked_api
, "1.0.0", None
),
470 (removed
, pushpop_unsafe
, "1.2.0", None
),
471 (removed
, allocator
, "1.0.0", None
),
472 // Allows the `#[simd]` attribute -- removed in favor of `#[repr(simd)]`
473 (removed
, simd
, "1.0.0", Some(27731)),
477 (stable_removed
, no_stack_check
, "1.0.0", None
),
481 (accepted
, associated_types
, "1.0.0", None
),
482 // allow overloading augmented assignment operations like `a += b`
483 (accepted
, augmented_assignments
, "1.8.0", Some(28235)),
484 // allow empty structs and enum variants with braces
485 (accepted
, braced_empty_structs
, "1.8.0", Some(29720)),
486 (accepted
, default_type_params
, "1.0.0", None
),
487 (accepted
, globs
, "1.0.0", None
),
488 (accepted
, if_let
, "1.0.0", None
),
489 // A temporary feature gate used to enable parser extensions needed
490 // to bootstrap fix for #5723.
491 (accepted
, issue_5723_bootstrap
, "1.0.0", None
),
492 (accepted
, macro_rules
, "1.0.0", None
),
493 // Allows using #![no_std]
494 (accepted
, no_std
, "1.6.0", None
),
495 (accepted
, slicing_syntax
, "1.0.0", None
),
496 (accepted
, struct_variant
, "1.0.0", None
),
497 // These are used to test this portion of the compiler, they don't actually
499 (accepted
, test_accepted_feature
, "1.0.0", None
),
500 (accepted
, tuple_indexing
, "1.0.0", None
),
501 // Allows macros to appear in the type position.
502 (accepted
, type_macros
, "1.13.0", Some(27245)),
503 (accepted
, while_let
, "1.0.0", None
),
504 // Allows `#[deprecated]` attribute
505 (accepted
, deprecated
, "1.9.0", Some(29935)),
507 (accepted
, question_mark
, "1.13.0", Some(31436)),
508 // Allows `..` in tuple (struct) patterns
509 (accepted
, dotdot_in_tuple_patterns
, "1.14.0", Some(33627)),
510 (accepted
, item_like_imports
, "1.15.0", Some(35120)),
511 // Allows using `Self` and associated types in struct expressions and patterns.
512 (accepted
, more_struct_aliases
, "1.16.0", Some(37544)),
513 // elide `'static` lifetimes in `static`s and `const`s
514 (accepted
, static_in_const
, "1.17.0", Some(35897)),
515 // Allows field shorthands (`x` meaning `x: x`) in struct literal expressions.
516 (accepted
, field_init_shorthand
, "1.17.0", Some(37340)),
517 // Allows the definition recursive static items.
518 (accepted
, static_recursion
, "1.17.0", Some(29719)),
519 // pub(restricted) visibilities (RFC 1422)
520 (accepted
, pub_restricted
, "1.18.0", Some(32409)),
521 // The #![windows_subsystem] attribute
522 (accepted
, windows_subsystem
, "1.18.0", Some(37499)),
523 // Allows `break {expr}` with a value inside `loop`s.
524 (accepted
, loop_break_value
, "1.19.0", Some(37339)),
525 // Permits numeric fields in struct expressions and patterns.
526 (accepted
, relaxed_adts
, "1.19.0", Some(35626)),
527 // Coerces non capturing closures to function pointers
528 (accepted
, closure_to_fn_coercion
, "1.19.0", Some(39817)),
529 // Allows attributes on struct literal fields.
530 (accepted
, struct_field_attributes
, "1.20.0", Some(38814)),
531 // Allows the definition of associated constants in `trait` or `impl`
533 (accepted
, associated_consts
, "1.20.0", Some(29646)),
534 // Usage of the `compile_error!` macro
535 (accepted
, compile_error
, "1.20.0", Some(40872)),
536 // See rust-lang/rfcs#1414. Allows code like `let x: &'static u32 = &42` to work.
537 (accepted
, rvalue_static_promotion
, "1.21.0", Some(38865)),
538 // Allow Drop types in constants (RFC 1440)
539 (accepted
, drop_types_in_const
, "1.22.0", Some(33156)),
540 // Allows the sysV64 ABI to be specified on all platforms
541 // instead of just the platforms on which it is the C ABI
542 (accepted
, abi_sysv64
, "1.24.0", Some(36167)),
543 // Allows `repr(align(16))` struct attribute (RFC 1358)
544 (accepted
, repr_align
, "1.24.0", Some(33626)),
545 // allow '|' at beginning of match arms (RFC 1925)
546 (accepted
, match_beginning_vert
, "1.25.0", Some(44101)),
547 // Nested groups in `use` (RFC 2128)
548 (accepted
, use_nested_groups
, "1.25.0", Some(44494)),
551 // If you change this, please modify src/doc/unstable-book as well. You must
552 // move that documentation into the relevant place in the other docs, and
553 // remove the chapter on the flag.
555 #[derive(PartialEq, Copy, Clone, Debug)]
556 pub enum AttributeType
{
557 /// Normal, builtin attribute that is consumed
558 /// by the compiler before the unused_attribute check
561 /// Builtin attribute that may not be consumed by the compiler
562 /// before the unused_attribute check. These attributes
563 /// will be ignored by the unused_attribute lint
566 /// Builtin attribute that is only allowed at the crate level
570 pub enum AttributeGate
{
571 /// Is gated by a given feature gate, reason
572 /// and function to check if enabled
573 Gated(Stability
, &'
static str, &'
static str, fn(&Features
) -> bool
),
575 /// Ungated attribute, can be used on all release channels
580 fn is_deprecated(&self) -> bool
{
582 Gated(Stability
::Deprecated(_
), ..) => true,
588 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
591 // Argument is tracking issue link.
592 Deprecated(&'
static str),
596 impl ::std
::fmt
::Debug
for AttributeGate
{
597 fn fmt(&self, fmt
: &mut ::std
::fmt
::Formatter
) -> ::std
::fmt
::Result
{
599 Gated(ref stab
, name
, expl
, _
) =>
600 write
!(fmt
, "Gated({:?}, {}, {})", stab
, name
, expl
),
601 Ungated
=> write
!(fmt
, "Ungated")
606 macro_rules
! cfg_fn
{
607 ($field
: ident
) => {{
608 fn f(features
: &Features
) -> bool
{
611 f
as fn(&Features
) -> bool
615 pub fn deprecated_attributes() -> Vec
<&'
static (&'
static str, AttributeType
, AttributeGate
)> {
616 BUILTIN_ATTRIBUTES
.iter().filter(|a
| a
.2.is_deprecated
()).collect()
619 pub fn is_builtin_attr(attr
: &ast
::Attribute
) -> bool
{
620 BUILTIN_ATTRIBUTES
.iter().any(|&(builtin_name
, _
, _
)| attr
.check_name(builtin_name
))
623 // Attributes that have a special meaning to rustc or rustdoc
624 pub const BUILTIN_ATTRIBUTES
: &'
static [(&'
static str, AttributeType
, AttributeGate
)] = &[
627 ("warn", Normal
, Ungated
),
628 ("allow", Normal
, Ungated
),
629 ("forbid", Normal
, Ungated
),
630 ("deny", Normal
, Ungated
),
632 ("macro_reexport", Normal
, Ungated
),
633 ("macro_use", Normal
, Ungated
),
634 ("macro_export", Normal
, Ungated
),
635 ("plugin_registrar", Normal
, Ungated
),
637 ("cfg", Normal
, Ungated
),
638 ("cfg_attr", Normal
, Ungated
),
639 ("main", Normal
, Ungated
),
640 ("start", Normal
, Ungated
),
641 ("test", Normal
, Ungated
),
642 ("bench", Normal
, Ungated
),
643 ("repr", Normal
, Ungated
),
644 ("path", Normal
, Ungated
),
645 ("abi", Normal
, Ungated
),
646 ("automatically_derived", Normal
, Ungated
),
647 ("no_mangle", Normal
, Ungated
),
648 ("no_link", Normal
, Ungated
),
649 ("derive", Normal
, Ungated
),
650 ("should_panic", Normal
, Ungated
),
651 ("ignore", Normal
, Ungated
),
652 ("no_implicit_prelude", Normal
, Ungated
),
653 ("reexport_test_harness_main", Normal
, Ungated
),
654 ("link_args", Normal
, Gated(Stability
::Unstable
,
656 "the `link_args` attribute is experimental and not \
657 portable across platforms, it is recommended to \
658 use `#[link(name = \"foo\")] instead",
659 cfg_fn
!(link_args
))),
660 ("macro_escape", Normal
, Ungated
),
663 ("structural_match", Whitelisted
, Gated(Stability
::Unstable
,
665 "the semantics of constant patterns is \
667 cfg_fn
!(structural_match
))),
670 ("non_exhaustive", Whitelisted
, Gated(Stability
::Unstable
,
672 "non exhaustive is an experimental feature",
673 cfg_fn
!(non_exhaustive
))),
675 ("plugin", CrateLevel
, Gated(Stability
::Unstable
,
677 "compiler plugins are experimental \
681 ("no_std", CrateLevel
, Ungated
),
682 ("no_core", CrateLevel
, Gated(Stability
::Unstable
,
684 "no_core is experimental",
686 ("lang", Normal
, Gated(Stability
::Unstable
,
688 "language items are subject to change",
689 cfg_fn
!(lang_items
))),
690 ("linkage", Whitelisted
, Gated(Stability
::Unstable
,
692 "the `linkage` attribute is experimental \
693 and not portable across platforms",
695 ("thread_local", Whitelisted
, Gated(Stability
::Unstable
,
697 "`#[thread_local]` is an experimental feature, and does \
698 not currently handle destructors.",
699 cfg_fn
!(thread_local
))),
701 ("rustc_on_unimplemented", Normal
, Gated(Stability
::Unstable
,
703 "the `#[rustc_on_unimplemented]` attribute \
704 is an experimental feature",
705 cfg_fn
!(on_unimplemented
))),
706 ("rustc_const_unstable", Normal
, Gated(Stability
::Unstable
,
707 "rustc_const_unstable",
708 "the `#[rustc_const_unstable]` attribute \
709 is an internal feature",
710 cfg_fn
!(rustc_const_unstable
))),
711 ("global_allocator", Normal
, Gated(Stability
::Unstable
,
713 "the `#[global_allocator]` attribute is \
714 an experimental feature",
715 cfg_fn
!(global_allocator
))),
716 ("default_lib_allocator", Whitelisted
, Gated(Stability
::Unstable
,
717 "allocator_internals",
718 "the `#[default_lib_allocator]` \
719 attribute is an experimental feature",
720 cfg_fn
!(allocator_internals
))),
721 ("needs_allocator", Normal
, Gated(Stability
::Unstable
,
722 "allocator_internals",
723 "the `#[needs_allocator]` \
724 attribute is an experimental \
726 cfg_fn
!(allocator_internals
))),
727 ("panic_runtime", Whitelisted
, Gated(Stability
::Unstable
,
729 "the `#[panic_runtime]` attribute is \
730 an experimental feature",
731 cfg_fn
!(panic_runtime
))),
732 ("needs_panic_runtime", Whitelisted
, Gated(Stability
::Unstable
,
733 "needs_panic_runtime",
734 "the `#[needs_panic_runtime]` \
735 attribute is an experimental \
737 cfg_fn
!(needs_panic_runtime
))),
738 ("rustc_variance", Normal
, Gated(Stability
::Unstable
,
740 "the `#[rustc_variance]` attribute \
741 is just used for rustc unit tests \
742 and will never be stable",
743 cfg_fn
!(rustc_attrs
))),
744 ("rustc_regions", Normal
, Gated(Stability
::Unstable
,
746 "the `#[rustc_regions]` attribute \
747 is just used for rustc unit tests \
748 and will never be stable",
749 cfg_fn
!(rustc_attrs
))),
750 ("rustc_error", Whitelisted
, Gated(Stability
::Unstable
,
752 "the `#[rustc_error]` attribute \
753 is just used for rustc unit tests \
754 and will never be stable",
755 cfg_fn
!(rustc_attrs
))),
756 ("rustc_if_this_changed", Whitelisted
, Gated(Stability
::Unstable
,
758 "the `#[rustc_if_this_changed]` attribute \
759 is just used for rustc unit tests \
760 and will never be stable",
761 cfg_fn
!(rustc_attrs
))),
762 ("rustc_then_this_would_need", Whitelisted
, Gated(Stability
::Unstable
,
764 "the `#[rustc_if_this_changed]` attribute \
765 is just used for rustc unit tests \
766 and will never be stable",
767 cfg_fn
!(rustc_attrs
))),
768 ("rustc_dirty", Whitelisted
, Gated(Stability
::Unstable
,
770 "the `#[rustc_dirty]` attribute \
771 is just used for rustc unit tests \
772 and will never be stable",
773 cfg_fn
!(rustc_attrs
))),
774 ("rustc_clean", Whitelisted
, Gated(Stability
::Unstable
,
776 "the `#[rustc_clean]` attribute \
777 is just used for rustc unit tests \
778 and will never be stable",
779 cfg_fn
!(rustc_attrs
))),
780 ("rustc_partition_reused", Whitelisted
, Gated(Stability
::Unstable
,
783 is just used for rustc unit tests \
784 and will never be stable",
785 cfg_fn
!(rustc_attrs
))),
786 ("rustc_partition_translated", Whitelisted
, Gated(Stability
::Unstable
,
789 is just used for rustc unit tests \
790 and will never be stable",
791 cfg_fn
!(rustc_attrs
))),
792 ("rustc_serialize_exclude_null", Normal
, Gated(Stability
::Unstable
,
794 "the `#[rustc_serialize_exclude_null]` attribute \
795 is an internal-only feature",
796 cfg_fn
!(rustc_attrs
))),
797 ("rustc_synthetic", Whitelisted
, Gated(Stability
::Unstable
,
800 is just used for rustc unit tests \
801 and will never be stable",
802 cfg_fn
!(rustc_attrs
))),
803 ("rustc_symbol_name", Whitelisted
, Gated(Stability
::Unstable
,
805 "internal rustc attributes will never be stable",
806 cfg_fn
!(rustc_attrs
))),
807 ("rustc_item_path", Whitelisted
, Gated(Stability
::Unstable
,
809 "internal rustc attributes will never be stable",
810 cfg_fn
!(rustc_attrs
))),
811 ("rustc_mir", Whitelisted
, Gated(Stability
::Unstable
,
813 "the `#[rustc_mir]` attribute \
814 is just used for rustc unit tests \
815 and will never be stable",
816 cfg_fn
!(rustc_attrs
))),
817 ("rustc_inherit_overflow_checks", Whitelisted
, Gated(Stability
::Unstable
,
819 "the `#[rustc_inherit_overflow_checks]` \
820 attribute is just used to control \
821 overflow checking behavior of several \
822 libcore functions that are inlined \
823 across crates and will never be stable",
824 cfg_fn
!(rustc_attrs
))),
827 ("nll", Whitelisted
, Gated(Stability
::Unstable
,
829 "Non lexical lifetimes",
831 ("compiler_builtins", Whitelisted
, Gated(Stability
::Unstable
,
833 "the `#[compiler_builtins]` attribute is used to \
834 identify the `compiler_builtins` crate which \
835 contains compiler-rt intrinsics and will never be \
837 cfg_fn
!(compiler_builtins
))),
838 ("sanitizer_runtime", Whitelisted
, Gated(Stability
::Unstable
,
840 "the `#[sanitizer_runtime]` attribute is used to \
841 identify crates that contain the runtime of a \
842 sanitizer and will never be stable",
843 cfg_fn
!(sanitizer_runtime
))),
844 ("profiler_runtime", Whitelisted
, Gated(Stability
::Unstable
,
846 "the `#[profiler_runtime]` attribute is used to \
847 identify the `profiler_builtins` crate which \
848 contains the profiler runtime and will never be \
850 cfg_fn
!(profiler_runtime
))),
852 ("allow_internal_unstable", Normal
, Gated(Stability
::Unstable
,
853 "allow_internal_unstable",
854 EXPLAIN_ALLOW_INTERNAL_UNSTABLE
,
855 cfg_fn
!(allow_internal_unstable
))),
857 ("allow_internal_unsafe", Normal
, Gated(Stability
::Unstable
,
858 "allow_internal_unsafe",
859 EXPLAIN_ALLOW_INTERNAL_UNSAFE
,
860 cfg_fn
!(allow_internal_unsafe
))),
862 ("fundamental", Whitelisted
, Gated(Stability
::Unstable
,
864 "the `#[fundamental]` attribute \
865 is an experimental feature",
866 cfg_fn
!(fundamental
))),
868 ("proc_macro_derive", Normal
, Ungated
),
870 ("rustc_copy_clone_marker", Whitelisted
, Gated(Stability
::Unstable
,
872 "internal implementation detail",
873 cfg_fn
!(rustc_attrs
))),
875 // FIXME: #14408 whitelist docs since rustdoc looks at them
876 ("doc", Whitelisted
, Ungated
),
878 // FIXME: #14406 these are processed in trans, which happens after the
880 ("cold", Whitelisted
, Ungated
),
881 ("naked", Whitelisted
, Gated(Stability
::Unstable
,
883 "the `#[naked]` attribute \
884 is an experimental feature",
885 cfg_fn
!(naked_functions
))),
886 ("target_feature", Whitelisted
, Gated(
887 Stability
::Unstable
, "target_feature",
888 "the `#[target_feature]` attribute is an experimental feature",
889 cfg_fn
!(target_feature
))),
890 ("export_name", Whitelisted
, Ungated
),
891 ("inline", Whitelisted
, Ungated
),
892 ("link", Whitelisted
, Ungated
),
893 ("link_name", Whitelisted
, Ungated
),
894 ("link_section", Whitelisted
, Ungated
),
895 ("no_builtins", Whitelisted
, Ungated
),
896 ("no_mangle", Whitelisted
, Ungated
),
897 ("no_debug", Whitelisted
, Gated(
898 Stability
::Deprecated("https://github.com/rust-lang/rust/issues/29721"),
900 "the `#[no_debug]` attribute was an experimental feature that has been \
901 deprecated due to lack of demand",
903 ("omit_gdb_pretty_printer_section", Whitelisted
, Gated(Stability
::Unstable
,
904 "omit_gdb_pretty_printer_section",
905 "the `#[omit_gdb_pretty_printer_section]` \
906 attribute is just used for the Rust test \
908 cfg_fn
!(omit_gdb_pretty_printer_section
))),
909 ("unsafe_destructor_blind_to_params",
911 Gated(Stability
::Deprecated("https://github.com/rust-lang/rust/issues/34761"),
912 "dropck_parametricity",
913 "unsafe_destructor_blind_to_params has been replaced by \
914 may_dangle and will be removed in the future",
915 cfg_fn
!(dropck_parametricity
))),
918 Gated(Stability
::Unstable
,
920 "may_dangle has unstable semantics and may be removed in the future",
921 cfg_fn
!(dropck_eyepatch
))),
922 ("unwind", Whitelisted
, Gated(Stability
::Unstable
,
924 "#[unwind] is experimental",
925 cfg_fn
!(unwind_attributes
))),
926 ("used", Whitelisted
, Gated(
927 Stability
::Unstable
, "used",
928 "the `#[used]` attribute is an experimental feature",
932 ("prelude_import", Whitelisted
, Gated(Stability
::Unstable
,
934 "`#[prelude_import]` is for use by rustc only",
935 cfg_fn
!(prelude_import
))),
937 // FIXME: #14407 these are only looked at on-demand so we can't
938 // guarantee they'll have already been checked
939 ("rustc_deprecated", Whitelisted
, Ungated
),
940 ("must_use", Whitelisted
, Ungated
),
941 ("stable", Whitelisted
, Ungated
),
942 ("unstable", Whitelisted
, Ungated
),
943 ("deprecated", Normal
, Ungated
),
945 ("rustc_paren_sugar", Normal
, Gated(Stability
::Unstable
,
947 "unboxed_closures are still evolving",
948 cfg_fn
!(unboxed_closures
))),
950 ("windows_subsystem", Whitelisted
, Ungated
),
952 ("proc_macro_attribute", Normal
, Gated(Stability
::Unstable
,
954 "attribute proc macros are currently unstable",
955 cfg_fn
!(proc_macro
))),
957 ("proc_macro", Normal
, Gated(Stability
::Unstable
,
959 "function-like proc macros are currently unstable",
960 cfg_fn
!(proc_macro
))),
962 ("rustc_derive_registrar", Normal
, Gated(Stability
::Unstable
,
963 "rustc_derive_registrar",
964 "used internally by rustc",
965 cfg_fn
!(rustc_attrs
))),
967 ("allow_fail", Normal
, Gated(Stability
::Unstable
,
969 "allow_fail attribute is currently unstable",
970 cfg_fn
!(allow_fail
))),
972 ("rustc_std_internal_symbol", Whitelisted
, Gated(Stability
::Unstable
,
974 "this is an internal attribute that will \
976 cfg_fn
!(rustc_attrs
))),
978 // whitelists "identity-like" conversion methods to suggest on type mismatch
979 ("rustc_conversion_suggestion", Whitelisted
, Gated(Stability
::Unstable
,
981 "this is an internal attribute that will \
983 cfg_fn
!(rustc_attrs
))),
985 ("wasm_import_memory", Whitelisted
, Gated(Stability
::Unstable
,
986 "wasm_import_memory",
987 "wasm_import_memory attribute is currently unstable",
988 cfg_fn
!(wasm_import_memory
))),
990 ("rustc_args_required_const", Whitelisted
, Gated(Stability
::Unstable
,
992 "never will be stable",
993 cfg_fn
!(rustc_attrs
))),
995 // Crate level attributes
996 ("crate_name", CrateLevel
, Ungated
),
997 ("crate_type", CrateLevel
, Ungated
),
998 ("crate_id", CrateLevel
, Ungated
),
999 ("feature", CrateLevel
, Ungated
),
1000 ("no_start", CrateLevel
, Ungated
),
1001 ("no_main", CrateLevel
, Ungated
),
1002 ("no_builtins", CrateLevel
, Ungated
),
1003 ("recursion_limit", CrateLevel
, Ungated
),
1004 ("type_length_limit", CrateLevel
, Ungated
),
1007 // cfg(...)'s that are feature gated
1008 const GATED_CFGS
: &[(&str, &str, fn(&Features
) -> bool
)] = &[
1009 // (name in cfg, feature, function to check if the feature is enabled)
1010 ("target_feature", "cfg_target_feature", cfg_fn
!(cfg_target_feature
)),
1011 ("target_vendor", "cfg_target_vendor", cfg_fn
!(cfg_target_vendor
)),
1012 ("target_thread_local", "cfg_target_thread_local", cfg_fn
!(cfg_target_thread_local
)),
1013 ("target_has_atomic", "cfg_target_has_atomic", cfg_fn
!(cfg_target_has_atomic
)),
1016 #[derive(Debug, Eq, PartialEq)]
1017 pub struct GatedCfg
{
1023 pub fn gate(cfg
: &ast
::MetaItem
) -> Option
<GatedCfg
> {
1024 let name
= cfg
.name().as_str();
1026 .position(|info
| info
.0 == name
)
1035 pub fn check_and_emit(&self, sess
: &ParseSess
, features
: &Features
) {
1036 let (cfg
, feature
, has_feature
) = GATED_CFGS
[self.index
];
1037 if !has_feature(features
) && !self.span
.allows_unstable() {
1038 let explain
= format
!("`cfg({})` is experimental and subject to change", cfg
);
1039 emit_feature_err(sess
, feature
, self.span
, GateIssue
::Language
, &explain
);
1044 struct Context
<'a
> {
1045 features
: &'a Features
,
1046 parse_sess
: &'a ParseSess
,
1047 plugin_attributes
: &'a
[(String
, AttributeType
)],
1050 macro_rules
! gate_feature_fn
{
1051 ($cx
: expr
, $has_feature
: expr
, $span
: expr
, $name
: expr
, $explain
: expr
, $level
: expr
) => {{
1052 let (cx
, has_feature
, span
,
1053 name
, explain
, level
) = ($cx
, $has_feature
, $span
, $name
, $explain
, $level
);
1054 let has_feature
: bool
= has_feature(&$cx
.features
);
1055 debug
!("gate_feature(feature = {:?}, span = {:?}); has? {}", name
, span
, has_feature
);
1056 if !has_feature
&& !span
.allows_unstable() {
1057 leveled_feature_err(cx
.parse_sess
, name
, span
, GateIssue
::Language
, explain
, level
)
1063 macro_rules
! gate_feature
{
1064 ($cx
: expr
, $feature
: ident
, $span
: expr
, $explain
: expr
) => {
1065 gate_feature_fn
!($cx
, |x
:&Features
| x
.$feature
, $span
,
1066 stringify
!($feature
), $explain
, GateStrength
::Hard
)
1068 ($cx
: expr
, $feature
: ident
, $span
: expr
, $explain
: expr
, $level
: expr
) => {
1069 gate_feature_fn
!($cx
, |x
:&Features
| x
.$feature
, $span
,
1070 stringify
!($feature
), $explain
, $level
)
1074 impl<'a
> Context
<'a
> {
1075 fn check_attribute(&self, attr
: &ast
::Attribute
, is_macro
: bool
) {
1076 debug
!("check_attribute(attr = {:?})", attr
);
1077 let name
= unwrap_or
!(attr
.name(), return).as_str();
1078 for &(n
, ty
, ref gateage
) in BUILTIN_ATTRIBUTES
{
1080 if let Gated(_
, name
, desc
, ref has_feature
) = *gateage
{
1081 gate_feature_fn
!(self, has_feature
, attr
.span
, name
, desc
, GateStrength
::Hard
);
1082 } else if name
== "doc" {
1083 if let Some(content
) = attr
.meta_item_list() {
1084 if content
.iter().any(|c
| c
.check_name("include")) {
1085 gate_feature
!(self, external_doc
, attr
.span
,
1086 "#[doc(include = \"...\")] is experimental"
1091 debug
!("check_attribute: {:?} is builtin, {:?}, {:?}", attr
.path
, ty
, gateage
);
1095 for &(ref n
, ref ty
) in self.plugin_attributes
{
1096 if attr
.path
== &**n
{
1097 // Plugins can't gate attributes, so we don't check for it
1098 // unlike the code above; we only use this loop to
1099 // short-circuit to avoid the checks below
1100 debug
!("check_attribute: {:?} is registered by a plugin, {:?}", attr
.path
, ty
);
1104 if name
.starts_with("rustc_") {
1105 gate_feature
!(self, rustc_attrs
, attr
.span
,
1106 "unless otherwise specified, attributes \
1107 with the prefix `rustc_` \
1108 are reserved for internal compiler diagnostics");
1109 } else if name
.starts_with("derive_") {
1110 gate_feature
!(self, custom_derive
, attr
.span
, EXPLAIN_DERIVE_UNDERSCORE
);
1111 } else if !attr
::is_known(attr
) {
1112 // Only run the custom attribute lint during regular
1113 // feature gate checking. Macro gating runs
1114 // before the plugin attributes are registered
1115 // so we skip this then
1117 gate_feature
!(self, custom_attribute
, attr
.span
,
1118 &format
!("The attribute `{}` is currently \
1119 unknown to the compiler and \
1121 added to it in the future",
1128 pub fn check_attribute(attr
: &ast
::Attribute
, parse_sess
: &ParseSess
, features
: &Features
) {
1129 let cx
= Context { features: features, parse_sess: parse_sess, plugin_attributes: &[] }
;
1130 cx
.check_attribute(attr
, true);
1133 pub fn find_lang_feature_accepted_version(feature
: &str) -> Option
<&'
static str> {
1134 ACCEPTED_FEATURES
.iter().find(|t
| t
.0 == feature
).map(|t
| t
.1)
1137 fn find_lang_feature_issue(feature
: &str) -> Option
<u32> {
1138 if let Some(info
) = ACTIVE_FEATURES
.iter().find(|t
| t
.0 == feature
) {
1140 // FIXME (#28244): enforce that active features have issue numbers
1141 // assert!(issue.is_some())
1144 // search in Accepted, Removed, or Stable Removed features
1145 let found
= ACCEPTED_FEATURES
.iter().chain(REMOVED_FEATURES
).chain(STABLE_REMOVED_FEATURES
)
1146 .find(|t
| t
.0 == feature
);
1148 Some(&(_
, _
, issue
)) => issue
,
1149 None
=> panic
!("Feature `{}` is not declared anywhere", feature
),
1154 pub enum GateIssue
{
1156 Library(Option
<u32>)
1159 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
1160 pub enum GateStrength
{
1161 /// A hard error. (Most feature gates should use this.)
1163 /// Only a warning. (Use this only as backwards-compatibility demands.)
1167 pub fn emit_feature_err(sess
: &ParseSess
, feature
: &str, span
: Span
, issue
: GateIssue
,
1169 feature_err(sess
, feature
, span
, issue
, explain
).emit();
1172 pub fn feature_err
<'a
>(sess
: &'a ParseSess
, feature
: &str, span
: Span
, issue
: GateIssue
,
1173 explain
: &str) -> DiagnosticBuilder
<'a
> {
1174 leveled_feature_err(sess
, feature
, span
, issue
, explain
, GateStrength
::Hard
)
1177 fn leveled_feature_err
<'a
>(sess
: &'a ParseSess
, feature
: &str, span
: Span
, issue
: GateIssue
,
1178 explain
: &str, level
: GateStrength
) -> DiagnosticBuilder
<'a
> {
1179 let diag
= &sess
.span_diagnostic
;
1181 let issue
= match issue
{
1182 GateIssue
::Language
=> find_lang_feature_issue(feature
),
1183 GateIssue
::Library(lib
) => lib
,
1186 let explanation
= if let Some(n
) = issue
{
1187 format
!("{} (see issue #{})", explain
, n
)
1192 let mut err
= match level
{
1193 GateStrength
::Hard
=> {
1194 diag
.struct_span_err_with_code(span
, &explanation
, stringify_error_code
!(E0658
))
1196 GateStrength
::Soft
=> diag
.struct_span_warn(span
, &explanation
),
1199 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
1200 if sess
.unstable_features
.is_nightly_build() {
1201 err
.help(&format
!("add #![feature({})] to the \
1202 crate attributes to enable",
1206 // If we're on stable and only emitting a "soft" warning, add a note to
1207 // clarify that the feature isn't "on" (rather than being on but
1209 if !sess
.unstable_features
.is_nightly_build() && level
== GateStrength
::Soft
{
1210 err
.help("a nightly build of the compiler is required to enable this feature");
1217 const EXPLAIN_BOX_SYNTAX
: &'
static str =
1218 "box expression syntax is experimental; you can call `Box::new` instead.";
1220 pub const EXPLAIN_STMT_ATTR_SYNTAX
: &'
static str =
1221 "attributes on non-item statements and expressions are experimental.";
1223 pub const EXPLAIN_ASM
: &'
static str =
1224 "inline assembly is not stable enough for use and is subject to change";
1226 pub const EXPLAIN_GLOBAL_ASM
: &'
static str =
1227 "`global_asm!` is not stable enough for use and is subject to change";
1229 pub const EXPLAIN_LOG_SYNTAX
: &'
static str =
1230 "`log_syntax!` is not stable enough for use and is subject to change";
1232 pub const EXPLAIN_CONCAT_IDENTS
: &'
static str =
1233 "`concat_idents` is not stable enough for use and is subject to change";
1235 pub const EXPLAIN_TRACE_MACROS
: &'
static str =
1236 "`trace_macros` is not stable enough for use and is subject to change";
1237 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE
: &'
static str =
1238 "allow_internal_unstable side-steps feature gating and stability checks";
1239 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE
: &'
static str =
1240 "allow_internal_unsafe side-steps the unsafe_code lint";
1242 pub const EXPLAIN_CUSTOM_DERIVE
: &'
static str =
1243 "`#[derive]` for custom traits is deprecated and will be removed in the future.";
1245 pub const EXPLAIN_DEPR_CUSTOM_DERIVE
: &'
static str =
1246 "`#[derive]` for custom traits is deprecated and will be removed in the future. \
1247 Prefer using procedural macro custom derive.";
1249 pub const EXPLAIN_DERIVE_UNDERSCORE
: &'
static str =
1250 "attributes of the form `#[derive_*]` are reserved for the compiler";
1252 pub const EXPLAIN_VIS_MATCHER
: &'
static str =
1253 ":vis fragment specifier is experimental and subject to change";
1255 pub const EXPLAIN_LIFETIME_MATCHER
: &'
static str =
1256 ":lifetime fragment specifier is experimental and subject to change";
1258 pub const EXPLAIN_PLACEMENT_IN
: &'
static str =
1259 "placement-in expression syntax is experimental and subject to change.";
1261 pub const EXPLAIN_UNSIZED_TUPLE_COERCION
: &'
static str =
1262 "Unsized tuple coercion is not stable enough for use and is subject to change";
1264 pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP
: &'
static str =
1265 "Using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
1267 struct PostExpansionVisitor
<'a
> {
1268 context
: &'a Context
<'a
>,
1271 macro_rules
! gate_feature_post
{
1272 ($cx
: expr
, $feature
: ident
, $span
: expr
, $explain
: expr
) => {{
1273 let (cx
, span
) = ($cx
, $span
);
1274 if !span
.allows_unstable() {
1275 gate_feature
!(cx
.context
, $feature
, span
, $explain
)
1278 ($cx
: expr
, $feature
: ident
, $span
: expr
, $explain
: expr
, $level
: expr
) => {{
1279 let (cx
, span
) = ($cx
, $span
);
1280 if !span
.allows_unstable() {
1281 gate_feature
!(cx
.context
, $feature
, span
, $explain
, $level
)
1286 impl<'a
> PostExpansionVisitor
<'a
> {
1287 fn check_abi(&self, abi
: Abi
, span
: Span
) {
1289 Abi
::RustIntrinsic
=> {
1290 gate_feature_post
!(&self, intrinsics
, span
,
1291 "intrinsics are subject to change");
1293 Abi
::PlatformIntrinsic
=> {
1294 gate_feature_post
!(&self, platform_intrinsics
, span
,
1295 "platform intrinsics are experimental and possibly buggy");
1297 Abi
::Vectorcall
=> {
1298 gate_feature_post
!(&self, abi_vectorcall
, span
,
1299 "vectorcall is experimental and subject to change");
1302 gate_feature_post
!(&self, abi_thiscall
, span
,
1303 "thiscall is experimental and subject to change");
1306 gate_feature_post
!(&self, unboxed_closures
, span
,
1307 "rust-call ABI is subject to change");
1310 gate_feature_post
!(&self, abi_ptx
, span
,
1311 "PTX ABIs are experimental and subject to change");
1313 Abi
::Unadjusted
=> {
1314 gate_feature_post
!(&self, abi_unadjusted
, span
,
1315 "unadjusted ABI is an implementation detail and perma-unstable");
1317 Abi
::Msp430Interrupt
=> {
1318 gate_feature_post
!(&self, abi_msp430_interrupt
, span
,
1319 "msp430-interrupt ABI is experimental and subject to change");
1321 Abi
::X86Interrupt
=> {
1322 gate_feature_post
!(&self, abi_x86_interrupt
, span
,
1323 "x86-interrupt ABI is experimental and subject to change");
1339 fn contains_novel_literal(item
: &ast
::MetaItem
) -> bool
{
1340 use ast
::MetaItemKind
::*;
1341 use ast
::NestedMetaItemKind
::*;
1345 NameValue(ref lit
) => !lit
.node
.is_str(),
1346 List(ref list
) => list
.iter().any(|li
| {
1348 MetaItem(ref mi
) => contains_novel_literal(mi
),
1355 // Bans nested `impl Trait`, e.g. `impl Into<impl Debug>`.
1356 // Nested `impl Trait` _is_ allowed in associated type position,
1357 // e.g `impl Iterator<Item=impl Debug>`
1358 struct NestedImplTraitVisitor
<'a
> {
1359 context
: &'a Context
<'a
>,
1360 is_in_impl_trait
: bool
,
1363 impl<'a
> NestedImplTraitVisitor
<'a
> {
1364 fn with_impl_trait
<F
>(&mut self, is_in_impl_trait
: bool
, f
: F
)
1365 where F
: FnOnce(&mut NestedImplTraitVisitor
<'a
>)
1367 let old_is_in_impl_trait
= self.is_in_impl_trait
;
1368 self.is_in_impl_trait
= is_in_impl_trait
;
1370 self.is_in_impl_trait
= old_is_in_impl_trait
;
1375 impl<'a
> Visitor
<'a
> for NestedImplTraitVisitor
<'a
> {
1376 fn visit_ty(&mut self, t
: &'a ast
::Ty
) {
1377 if let ast
::TyKind
::ImplTrait(_
) = t
.node
{
1378 if self.is_in_impl_trait
{
1379 gate_feature_post
!(&self, nested_impl_trait
, t
.span
,
1380 "nested `impl Trait` is experimental"
1383 self.with_impl_trait(true, |this
| visit
::walk_ty(this
, t
));
1385 visit
::walk_ty(self, t
);
1388 fn visit_path_parameters(&mut self, _
: Span
, path_parameters
: &'a ast
::PathParameters
) {
1389 match *path_parameters
{
1390 ast
::PathParameters
::AngleBracketed(ref params
) => {
1391 for type_
in ¶ms
.types
{
1392 self.visit_ty(type_
);
1394 for type_binding
in ¶ms
.bindings
{
1395 // Type bindings such as `Item=impl Debug` in `Iterator<Item=Debug>`
1396 // are allowed to contain nested `impl Trait`.
1397 self.with_impl_trait(false, |this
| visit
::walk_ty(this
, &type_binding
.ty
));
1400 ast
::PathParameters
::Parenthesized(ref params
) => {
1401 for type_
in ¶ms
.inputs
{
1402 self.visit_ty(type_
);
1404 if let Some(ref type_
) = params
.output
{
1405 // `-> Foo` syntax is essentially an associated type binding,
1406 // so it is also allowed to contain nested `impl Trait`.
1407 self.with_impl_trait(false, |this
| visit
::walk_ty(this
, type_
));
1414 impl<'a
> PostExpansionVisitor
<'a
> {
1415 fn whole_crate_feature_gates(&mut self, krate
: &ast
::Crate
) {
1417 &mut NestedImplTraitVisitor
{
1418 context
: self.context
,
1419 is_in_impl_trait
: false,
1422 for &(ident
, span
) in &*self.context
.parse_sess
.non_modrs_mods
.borrow() {
1423 if !span
.allows_unstable() {
1424 let cx
= &self.context
;
1425 let level
= GateStrength
::Hard
;
1426 let has_feature
= cx
.features
.non_modrs_mods
;
1427 let name
= "non_modrs_mods";
1428 debug
!("gate_feature(feature = {:?}, span = {:?}); has? {}",
1429 name
, span
, has_feature
);
1431 if !has_feature
&& !span
.allows_unstable() {
1432 leveled_feature_err(
1433 cx
.parse_sess
, name
, span
, GateIssue
::Language
,
1434 "mod statements in non-mod.rs files are unstable", level
1436 .help(&format
!("on stable builds, rename this file to {}{}mod.rs",
1437 ident
, path
::MAIN_SEPARATOR
))
1445 impl<'a
> Visitor
<'a
> for PostExpansionVisitor
<'a
> {
1446 fn visit_attribute(&mut self, attr
: &ast
::Attribute
) {
1447 if !attr
.span
.allows_unstable() {
1448 // check for gated attributes
1449 self.context
.check_attribute(attr
, false);
1452 if attr
.check_name("doc") {
1453 if let Some(content
) = attr
.meta_item_list() {
1454 if content
.len() == 1 && content
[0].check_name("cfg") {
1455 gate_feature_post
!(&self, doc_cfg
, attr
.span
,
1456 "#[doc(cfg(...))] is experimental"
1458 } else if content
.iter().any(|c
| c
.check_name("masked")) {
1459 gate_feature_post
!(&self, doc_masked
, attr
.span
,
1460 "#[doc(masked)] is experimental"
1462 } else if content
.iter().any(|c
| c
.check_name("spotlight")) {
1463 gate_feature_post
!(&self, doc_spotlight
, attr
.span
,
1464 "#[doc(spotlight)] is experimental"
1470 // allow attr_literals in #[repr(align(x))]
1471 let mut is_repr_align
= false;
1472 if attr
.path
== "repr" {
1473 if let Some(content
) = attr
.meta_item_list() {
1474 is_repr_align
= content
.iter().any(|c
| c
.check_name("align"));
1478 if self.context
.features
.proc_macro
&& attr
::is_known(attr
) {
1483 let meta
= panictry
!(attr
.parse_meta(self.context
.parse_sess
));
1484 if contains_novel_literal(&meta
) {
1485 gate_feature_post
!(&self, attr_literals
, attr
.span
,
1486 "non-string literals in attributes, or string \
1487 literals in top-level positions, are experimental");
1492 fn visit_name(&mut self, sp
: Span
, name
: ast
::Name
) {
1493 if !name
.as_str().is_ascii() {
1494 gate_feature_post
!(&self,
1496 self.context
.parse_sess
.codemap().def_span(sp
),
1497 "non-ascii idents are not fully supported.");
1501 fn visit_item(&mut self, i
: &'a ast
::Item
) {
1503 ast
::ItemKind
::ExternCrate(_
) => {
1504 if let Some(attr
) = attr
::find_by_name(&i
.attrs
[..], "macro_reexport") {
1505 gate_feature_post
!(&self, macro_reexport
, attr
.span
,
1506 "macros re-exports are experimental \
1507 and possibly buggy");
1511 ast
::ItemKind
::ForeignMod(ref foreign_module
) => {
1512 self.check_abi(foreign_module
.abi
, i
.span
);
1515 ast
::ItemKind
::Fn(..) => {
1516 if attr
::contains_name(&i
.attrs
[..], "plugin_registrar") {
1517 gate_feature_post
!(&self, plugin_registrar
, i
.span
,
1518 "compiler plugins are experimental and possibly buggy");
1520 if attr
::contains_name(&i
.attrs
[..], "start") {
1521 gate_feature_post
!(&self, start
, i
.span
,
1522 "a #[start] function is an experimental \
1523 feature whose signature may change \
1526 if attr
::contains_name(&i
.attrs
[..], "main") {
1527 gate_feature_post
!(&self, main
, i
.span
,
1528 "declaration of a nonstandard #[main] \
1529 function may change over time, for now \
1530 a top-level `fn main()` is required");
1532 if let Some(attr
) = attr
::find_by_name(&i
.attrs
[..], "must_use") {
1533 gate_feature_post
!(&self, fn_must_use
, attr
.span
,
1534 "`#[must_use]` on functions is experimental",
1535 GateStrength
::Soft
);
1539 ast
::ItemKind
::Struct(..) => {
1540 if let Some(attr
) = attr
::find_by_name(&i
.attrs
[..], "repr") {
1541 for item
in attr
.meta_item_list().unwrap_or_else(Vec
::new
) {
1542 if item
.check_name("simd") {
1543 gate_feature_post
!(&self, repr_simd
, attr
.span
,
1544 "SIMD types are experimental and possibly buggy");
1546 if item
.check_name("transparent") {
1547 gate_feature_post
!(&self, repr_transparent
, attr
.span
,
1548 "the `#[repr(transparent)]` attribute \
1555 ast
::ItemKind
::TraitAlias(..) => {
1556 gate_feature_post
!(&self, trait_alias
,
1558 "trait aliases are not yet fully implemented");
1561 ast
::ItemKind
::Impl(_
, polarity
, defaultness
, _
, _
, _
, ref impl_items
) => {
1562 if polarity
== ast
::ImplPolarity
::Negative
{
1563 gate_feature_post
!(&self, optin_builtin_traits
,
1565 "negative trait bounds are not yet fully implemented; \
1566 use marker types for now");
1569 if let ast
::Defaultness
::Default
= defaultness
{
1570 gate_feature_post
!(&self, specialization
,
1572 "specialization is unstable");
1575 for impl_item
in impl_items
{
1576 if let ast
::ImplItemKind
::Method(..) = impl_item
.node
{
1577 if let Some(attr
) = attr
::find_by_name(&impl_item
.attrs
[..], "must_use") {
1578 gate_feature_post
!(&self, fn_must_use
, attr
.span
,
1579 "`#[must_use]` on methods is experimental",
1580 GateStrength
::Soft
);
1586 ast
::ItemKind
::Trait(ast
::IsAuto
::Yes
, ..) => {
1587 gate_feature_post
!(&self, optin_builtin_traits
,
1589 "auto traits are experimental and possibly buggy");
1592 ast
::ItemKind
::MacroDef(ast
::MacroDef { legacy: false, .. }
) => {
1593 let msg
= "`macro` is experimental";
1594 gate_feature_post
!(&self, decl_macro
, i
.span
, msg
);
1600 visit
::walk_item(self, i
);
1603 fn visit_foreign_item(&mut self, i
: &'a ast
::ForeignItem
) {
1605 ast
::ForeignItemKind
::Fn(..) |
1606 ast
::ForeignItemKind
::Static(..) => {
1607 let link_name
= attr
::first_attr_value_str_by_name(&i
.attrs
, "link_name");
1608 let links_to_llvm
= match link_name
{
1609 Some(val
) => val
.as_str().starts_with("llvm."),
1613 gate_feature_post
!(&self, link_llvm_intrinsics
, i
.span
,
1614 "linking to LLVM intrinsics is experimental");
1617 ast
::ForeignItemKind
::Ty
=> {
1618 gate_feature_post
!(&self, extern_types
, i
.span
,
1619 "extern types are experimental");
1623 visit
::walk_foreign_item(self, i
)
1626 fn visit_ty(&mut self, ty
: &'a ast
::Ty
) {
1628 ast
::TyKind
::BareFn(ref bare_fn_ty
) => {
1629 self.check_abi(bare_fn_ty
.abi
, ty
.span
);
1631 ast
::TyKind
::Never
=> {
1632 gate_feature_post
!(&self, never_type
, ty
.span
,
1633 "The `!` type is experimental");
1635 ast
::TyKind
::TraitObject(_
, ast
::TraitObjectSyntax
::Dyn
) => {
1636 gate_feature_post
!(&self, dyn_trait
, ty
.span
,
1637 "`dyn Trait` syntax is unstable");
1641 visit
::walk_ty(self, ty
)
1644 fn visit_fn_ret_ty(&mut self, ret_ty
: &'a ast
::FunctionRetTy
) {
1645 if let ast
::FunctionRetTy
::Ty(ref output_ty
) = *ret_ty
{
1646 if output_ty
.node
!= ast
::TyKind
::Never
{
1647 self.visit_ty(output_ty
)
1652 fn visit_expr(&mut self, e
: &'a ast
::Expr
) {
1654 ast
::ExprKind
::Box(_
) => {
1655 gate_feature_post
!(&self, box_syntax
, e
.span
, EXPLAIN_BOX_SYNTAX
);
1657 ast
::ExprKind
::Type(..) => {
1658 gate_feature_post
!(&self, type_ascription
, e
.span
,
1659 "type ascription is experimental");
1661 ast
::ExprKind
::Range(_
, _
, ast
::RangeLimits
::Closed
) => {
1662 gate_feature_post
!(&self, inclusive_range_syntax
,
1664 "inclusive range syntax is experimental");
1666 ast
::ExprKind
::InPlace(..) => {
1667 gate_feature_post
!(&self, placement_in_syntax
, e
.span
, EXPLAIN_PLACEMENT_IN
);
1669 ast
::ExprKind
::Yield(..) => {
1670 gate_feature_post
!(&self, generators
,
1672 "yield syntax is experimental");
1674 ast
::ExprKind
::Lit(ref lit
) => {
1675 if let ast
::LitKind
::Int(_
, ref ty
) = lit
.node
{
1677 ast
::LitIntType
::Signed(ast
::IntTy
::I128
) |
1678 ast
::LitIntType
::Unsigned(ast
::UintTy
::U128
) => {
1679 gate_feature_post
!(&self, i128_type
, e
.span
,
1680 "128-bit integers are not stable");
1686 ast
::ExprKind
::Catch(_
) => {
1687 gate_feature_post
!(&self, catch_expr
, e
.span
, "`catch` expression is experimental");
1691 visit
::walk_expr(self, e
);
1694 fn visit_arm(&mut self, arm
: &'a ast
::Arm
) {
1695 visit
::walk_arm(self, arm
)
1698 fn visit_pat(&mut self, pattern
: &'a ast
::Pat
) {
1699 match pattern
.node
{
1700 PatKind
::Slice(_
, Some(_
), ref last
) if !last
.is_empty() => {
1701 gate_feature_post
!(&self, advanced_slice_patterns
,
1703 "multiple-element slice matches anywhere \
1704 but at the end of a slice (e.g. \
1705 `[0, ..xs, 0]`) are experimental")
1707 PatKind
::Slice(..) => {
1708 gate_feature_post
!(&self, slice_patterns
,
1710 "slice pattern syntax is experimental");
1712 PatKind
::Box(..) => {
1713 gate_feature_post
!(&self, box_patterns
,
1715 "box pattern syntax is experimental");
1717 PatKind
::Range(_
, _
, RangeEnd
::Excluded
) => {
1718 gate_feature_post
!(&self, exclusive_range_pattern
, pattern
.span
,
1719 "exclusive range pattern syntax is experimental");
1721 PatKind
::Range(_
, _
, RangeEnd
::Included(RangeSyntax
::DotDotEq
)) => {
1722 gate_feature_post
!(&self, dotdoteq_in_patterns
, pattern
.span
,
1723 "`..=` syntax in patterns is experimental");
1727 visit
::walk_pat(self, pattern
)
1730 fn visit_fn(&mut self,
1731 fn_kind
: FnKind
<'a
>,
1732 fn_decl
: &'a ast
::FnDecl
,
1735 // check for const fn declarations
1736 if let FnKind
::ItemFn(_
, _
, Spanned { node: ast::Constness::Const, .. }
, _
, _
, _
) =
1738 gate_feature_post
!(&self, const_fn
, span
, "const fn is unstable");
1740 // stability of const fn methods are covered in
1741 // visit_trait_item and visit_impl_item below; this is
1742 // because default methods don't pass through this
1746 FnKind
::ItemFn(_
, _
, _
, abi
, _
, _
) |
1747 FnKind
::Method(_
, &ast
::MethodSig { abi, .. }
, _
, _
) => {
1748 self.check_abi(abi
, span
);
1752 visit
::walk_fn(self, fn_kind
, fn_decl
, span
);
1755 fn visit_trait_item(&mut self, ti
: &'a ast
::TraitItem
) {
1757 ast
::TraitItemKind
::Method(ref sig
, ref block
) => {
1758 if block
.is_none() {
1759 self.check_abi(sig
.abi
, ti
.span
);
1761 if sig
.constness
.node
== ast
::Constness
::Const
{
1762 gate_feature_post
!(&self, const_fn
, ti
.span
, "const fn is unstable");
1765 ast
::TraitItemKind
::Type(_
, ref default) => {
1766 // We use two if statements instead of something like match guards so that both
1767 // of these errors can be emitted if both cases apply.
1768 if default.is_some() {
1769 gate_feature_post
!(&self, associated_type_defaults
, ti
.span
,
1770 "associated type defaults are unstable");
1772 if ti
.generics
.is_parameterized() {
1773 gate_feature_post
!(&self, generic_associated_types
, ti
.span
,
1774 "generic associated types are unstable");
1779 visit
::walk_trait_item(self, ti
);
1782 fn visit_impl_item(&mut self, ii
: &'a ast
::ImplItem
) {
1783 if ii
.defaultness
== ast
::Defaultness
::Default
{
1784 gate_feature_post
!(&self, specialization
,
1786 "specialization is unstable");
1790 ast
::ImplItemKind
::Method(ref sig
, _
) => {
1791 if sig
.constness
.node
== ast
::Constness
::Const
{
1792 gate_feature_post
!(&self, const_fn
, ii
.span
, "const fn is unstable");
1795 ast
::ImplItemKind
::Type(_
) if ii
.generics
.is_parameterized() => {
1796 gate_feature_post
!(&self, generic_associated_types
, ii
.span
,
1797 "generic associated types are unstable");
1801 visit
::walk_impl_item(self, ii
);
1804 fn visit_path(&mut self, path
: &'a ast
::Path
, _id
: NodeId
) {
1805 for segment
in &path
.segments
{
1806 if segment
.identifier
.name
== keywords
::Crate
.name() {
1807 gate_feature_post
!(&self, crate_in_paths
, segment
.span
,
1808 "`crate` in paths is experimental");
1809 } else if segment
.identifier
.name
== keywords
::Extern
.name() {
1810 gate_feature_post
!(&self, extern_in_paths
, segment
.span
,
1811 "`extern` in paths is experimental");
1815 visit
::walk_path(self, path
);
1818 fn visit_vis(&mut self, vis
: &'a ast
::Visibility
) {
1819 if let ast
::Visibility
::Crate(span
, ast
::CrateSugar
::JustCrate
) = *vis
{
1820 gate_feature_post
!(&self, crate_visibility_modifier
, span
,
1821 "`crate` visibility modifier is experimental");
1823 visit
::walk_vis(self, vis
);
1826 fn visit_generic_param(&mut self, param
: &'a ast
::GenericParam
) {
1827 let (attrs
, explain
) = match *param
{
1828 ast
::GenericParam
::Lifetime(ref ld
) =>
1829 (&ld
.attrs
, "attributes on lifetime bindings are experimental"),
1830 ast
::GenericParam
::Type(ref t
) =>
1831 (&t
.attrs
, "attributes on type parameter bindings are experimental"),
1834 if !attrs
.is_empty() {
1835 gate_feature_post
!(&self, generic_param_attrs
, attrs
[0].span
, explain
);
1838 visit
::walk_generic_param(self, param
)
1841 fn visit_lifetime(&mut self, lt
: &'a ast
::Lifetime
) {
1842 if lt
.ident
.name
== "'_" {
1843 gate_feature_post
!(&self, underscore_lifetimes
, lt
.span
,
1844 "underscore lifetimes are unstable");
1846 visit
::walk_lifetime(self, lt
)
1850 pub fn get_features(span_handler
: &Handler
, krate_attrs
: &[ast
::Attribute
]) -> Features
{
1851 let mut features
= Features
::new();
1853 let mut feature_checker
= FeatureChecker
::default();
1855 for attr
in krate_attrs
{
1856 if !attr
.check_name("feature") {
1860 match attr
.meta_item_list() {
1862 span_err
!(span_handler
, attr
.span
, E0555
,
1863 "malformed feature attribute, expected #![feature(...)]");
1867 let name
= if let Some(word
) = mi
.word() {
1870 span_err
!(span_handler
, mi
.span
, E0556
,
1871 "malformed feature, expected just one word");
1875 if let Some(&(_
, _
, _
, set
)) = ACTIVE_FEATURES
.iter()
1876 .find(|& &(n
, _
, _
, _
)| name
== n
) {
1877 set(&mut features
, mi
.span
);
1878 feature_checker
.collect(&features
, mi
.span
);
1880 else if let Some(&(_
, _
, _
)) = REMOVED_FEATURES
.iter()
1881 .find(|& &(n
, _
, _
)| name
== n
)
1882 .or_else(|| STABLE_REMOVED_FEATURES
.iter()
1883 .find(|& &(n
, _
, _
)| name
== n
)) {
1884 span_err
!(span_handler
, mi
.span
, E0557
, "feature has been removed");
1886 else if let Some(&(_
, _
, _
)) = ACCEPTED_FEATURES
.iter()
1887 .find(|& &(n
, _
, _
)| name
== n
) {
1888 features
.declared_stable_lang_features
.push((name
, mi
.span
));
1890 features
.declared_lib_features
.push((name
, mi
.span
));
1897 feature_checker
.check(span_handler
);
1902 /// A collector for mutually exclusive and interdependent features and their flag spans.
1904 struct FeatureChecker
{
1905 proc_macro
: Option
<Span
>,
1906 custom_attribute
: Option
<Span
>,
1907 copy_closures
: Option
<Span
>,
1908 clone_closures
: Option
<Span
>,
1911 impl FeatureChecker
{
1912 // If this method turns out to be a hotspot due to branching,
1913 // the branching can be eliminated by modifying `set!()` to set these spans
1914 // only for the features that need to be checked for mutual exclusion.
1915 fn collect(&mut self, features
: &Features
, span
: Span
) {
1916 if features
.proc_macro
{
1917 // If self.proc_macro is None, set to Some(span)
1918 self.proc_macro
= self.proc_macro
.or(Some(span
));
1921 if features
.custom_attribute
{
1922 self.custom_attribute
= self.custom_attribute
.or(Some(span
));
1925 if features
.copy_closures
{
1926 self.copy_closures
= self.copy_closures
.or(Some(span
));
1929 if features
.clone_closures
{
1930 self.clone_closures
= self.clone_closures
.or(Some(span
));
1934 fn check(self, handler
: &Handler
) {
1935 if let (Some(pm_span
), Some(ca_span
)) = (self.proc_macro
, self.custom_attribute
) {
1936 handler
.struct_span_err(pm_span
, "Cannot use `#![feature(proc_macro)]` and \
1937 `#![feature(custom_attribute)] at the same time")
1938 .span_note(ca_span
, "`#![feature(custom_attribute)]` declared here")
1944 if let (Some(span
), None
) = (self.copy_closures
, self.clone_closures
) {
1945 handler
.struct_span_err(span
, "`#![feature(copy_closures)]` can only be used with \
1946 `#![feature(clone_closures)]`")
1947 .span_note(span
, "`#![feature(copy_closures)]` declared here")
1955 pub fn check_crate(krate
: &ast
::Crate
,
1957 features
: &Features
,
1958 plugin_attributes
: &[(String
, AttributeType
)],
1959 unstable
: UnstableFeatures
) {
1960 maybe_stage_features(&sess
.span_diagnostic
, krate
, unstable
);
1966 let visitor
= &mut PostExpansionVisitor { context: &ctx }
;
1967 visitor
.whole_crate_feature_gates(krate
);
1968 visit
::walk_crate(visitor
, krate
);
1971 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
1972 pub enum UnstableFeatures
{
1973 /// Hard errors for unstable features are active, as on
1974 /// beta/stable channels.
1976 /// Allow features to be activated, as on nightly.
1978 /// Errors are bypassed for bootstrapping. This is required any time
1979 /// during the build that feature-related lints are set to warn or above
1980 /// because the build turns on warnings-as-errors and uses lots of unstable
1981 /// features. As a result, this is always required for building Rust itself.
1985 impl UnstableFeatures
{
1986 pub fn from_environment() -> UnstableFeatures
{
1987 // Whether this is a feature-staged build, i.e. on the beta or stable channel
1988 let disable_unstable_features
= option_env
!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
1989 // Whether we should enable unstable features for bootstrapping
1990 let bootstrap
= env
::var("RUSTC_BOOTSTRAP").is_ok();
1991 match (disable_unstable_features
, bootstrap
) {
1992 (_
, true) => UnstableFeatures
::Cheat
,
1993 (true, _
) => UnstableFeatures
::Disallow
,
1994 (false, _
) => UnstableFeatures
::Allow
1998 pub fn is_nightly_build(&self) -> bool
{
2000 UnstableFeatures
::Allow
| UnstableFeatures
::Cheat
=> true,
2006 fn maybe_stage_features(span_handler
: &Handler
, krate
: &ast
::Crate
,
2007 unstable
: UnstableFeatures
) {
2008 let allow_features
= match unstable
{
2009 UnstableFeatures
::Allow
=> true,
2010 UnstableFeatures
::Disallow
=> false,
2011 UnstableFeatures
::Cheat
=> true
2013 if !allow_features
{
2014 for attr
in &krate
.attrs
{
2015 if attr
.check_name("feature") {
2016 let release_channel
= option_env
!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)");
2017 span_err
!(span_handler
, attr
.span
, E0554
,
2018 "#![feature] may not be used on the {} release channel",