1 use super::{active::{ACTIVE_FEATURES, Features}, Feature, State as FeatureState};
2 use super::accepted::ACCEPTED_FEATURES;
3 use super::removed::{REMOVED_FEATURES, STABLE_REMOVED_FEATURES};
4 use super::builtin_attrs::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
7 self, AssocTyConstraint, AssocTyConstraintKind, NodeId, GenericParam, GenericParamKind,
8 PatKind, RangeEnd, VariantData,
10 use crate::attr::{self, check_builtin_attribute};
11 use crate::source_map::Spanned;
12 use crate::edition::{ALL_EDITIONS, Edition};
13 use crate::visit::{self, FnKind, Visitor};
15 use crate::sess::ParseSess;
16 use crate::symbol::{Symbol, sym};
17 use crate::tokenstream::TokenTree;
19 use errors::{Applicability, DiagnosticBuilder, Handler};
20 use rustc_data_structures::fx::FxHashMap;
21 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
26 #[derive(Copy, Clone, Debug)]
29 // First argument is tracking issue link; second argument is an optional
30 // help message, which defaults to "remove this attribute"
31 Deprecated(&'static str, Option<&'static str>),
34 macro_rules! gate_feature_fn {
35 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $level: expr) => {{
36 let (cx, has_feature, span,
37 name, explain, level) = (&*$cx, $has_feature, $span, $name, $explain, $level);
38 let has_feature: bool = has_feature(&$cx.features);
39 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
40 if !has_feature && !span.allows_unstable($name) {
41 leveled_feature_err(cx.parse_sess, name, span, GateIssue::Language, explain, level)
47 macro_rules! gate_feature {
48 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
49 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
50 sym::$feature, $explain, GateStrength::Hard)
52 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {
53 gate_feature_fn!($cx, |x:&Features| x.$feature, $span,
54 sym::$feature, $explain, $level)
58 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
59 PostExpansionVisitor { parse_sess, features }.visit_attribute(attr)
62 fn find_lang_feature_issue(feature: Symbol) -> Option<u32> {
63 if let Some(info) = ACTIVE_FEATURES.iter().find(|t| t.name == feature) {
64 // FIXME (#28244): enforce that active features have issue numbers
65 // assert!(info.issue.is_some())
68 // search in Accepted, Removed, or Stable Removed features
69 let found = ACCEPTED_FEATURES.iter().chain(REMOVED_FEATURES).chain(STABLE_REMOVED_FEATURES)
70 .find(|t| t.name == feature);
72 Some(&Feature { issue, .. }) => issue,
73 None => panic!("Feature `{}` is not declared anywhere", feature),
83 #[derive(Debug, Copy, Clone, PartialEq)]
84 pub enum GateStrength {
85 /// A hard error. (Most feature gates should use this.)
87 /// Only a warning. (Use this only as backwards-compatibility demands.)
91 pub fn emit_feature_err(
98 feature_err(sess, feature, span, issue, explain).emit();
101 pub fn feature_err<'a, S: Into<MultiSpan>>(
107 ) -> DiagnosticBuilder<'a> {
108 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
111 fn leveled_feature_err<'a, S: Into<MultiSpan>>(
118 ) -> DiagnosticBuilder<'a> {
119 let diag = &sess.span_diagnostic;
121 let issue = match issue {
122 GateIssue::Language => find_lang_feature_issue(feature),
123 GateIssue::Library(lib) => lib,
126 let mut err = match level {
127 GateStrength::Hard => {
128 diag.struct_span_err_with_code(span, explain, stringify_error_code!(E0658))
130 GateStrength::Soft => diag.struct_span_warn(span, explain),
134 None | Some(0) => {} // We still accept `0` as a stand-in for backwards compatibility
137 "for more information, see https://github.com/rust-lang/rust/issues/{}",
143 // #23973: do not suggest `#![feature(...)]` if we are in beta/stable
144 if sess.unstable_features.is_nightly_build() {
145 err.help(&format!("add `#![feature({})]` to the crate attributes to enable", feature));
148 // If we're on stable and only emitting a "soft" warning, add a note to
149 // clarify that the feature isn't "on" (rather than being on but
151 if !sess.unstable_features.is_nightly_build() && level == GateStrength::Soft {
152 err.help("a nightly build of the compiler is required to enable this feature");
159 const EXPLAIN_BOX_SYNTAX: &str =
160 "box expression syntax is experimental; you can call `Box::new` instead";
162 pub const EXPLAIN_STMT_ATTR_SYNTAX: &str =
163 "attributes on expressions are experimental";
165 pub const EXPLAIN_ALLOW_INTERNAL_UNSTABLE: &str =
166 "allow_internal_unstable side-steps feature gating and stability checks";
167 pub const EXPLAIN_ALLOW_INTERNAL_UNSAFE: &str =
168 "allow_internal_unsafe side-steps the unsafe_code lint";
170 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &str =
171 "unsized tuple coercion is not stable enough for use and is subject to change";
173 struct PostExpansionVisitor<'a> {
174 parse_sess: &'a ParseSess,
175 features: &'a Features,
178 macro_rules! gate_feature_post {
179 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {{
180 let (cx, span) = ($cx, $span);
181 if !span.allows_unstable(sym::$feature) {
182 gate_feature!(cx, $feature, span, $explain)
185 ($cx: expr, $feature: ident, $span: expr, $explain: expr, $level: expr) => {{
186 let (cx, span) = ($cx, $span);
187 if !span.allows_unstable(sym::$feature) {
188 gate_feature!(cx, $feature, span, $explain, $level)
193 impl<'a> PostExpansionVisitor<'a> {
194 fn check_abi(&self, abi: ast::Abi) {
195 let ast::Abi { symbol, span } = abi;
197 match &*symbol.as_str() {
208 "rust-intrinsic" => {
209 gate_feature_post!(&self, intrinsics, span,
210 "intrinsics are subject to change");
212 "platform-intrinsic" => {
213 gate_feature_post!(&self, platform_intrinsics, span,
214 "platform intrinsics are experimental and possibly buggy");
217 gate_feature_post!(&self, abi_vectorcall, span,
218 "vectorcall is experimental and subject to change");
221 gate_feature_post!(&self, abi_thiscall, span,
222 "thiscall is experimental and subject to change");
225 gate_feature_post!(&self, unboxed_closures, span,
226 "rust-call ABI is subject to change");
229 gate_feature_post!(&self, abi_ptx, span,
230 "PTX ABIs are experimental and subject to change");
233 gate_feature_post!(&self, abi_unadjusted, span,
234 "unadjusted ABI is an implementation detail and perma-unstable");
236 "msp430-interrupt" => {
237 gate_feature_post!(&self, abi_msp430_interrupt, span,
238 "msp430-interrupt ABI is experimental and subject to change");
241 gate_feature_post!(&self, abi_x86_interrupt, span,
242 "x86-interrupt ABI is experimental and subject to change");
245 gate_feature_post!(&self, abi_amdgpu_kernel, span,
246 "amdgpu-kernel ABI is experimental and subject to change");
249 gate_feature_post!(&self, abi_efiapi, span,
250 "efiapi ABI is experimental and subject to change");
253 self.parse_sess.span_diagnostic.delay_span_bug(
255 &format!("unrecognized ABI not caught in lowering: {}", abi),
261 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
262 let has_fields = variants.iter().any(|variant| match variant.data {
263 VariantData::Tuple(..) | VariantData::Struct(..) => true,
264 VariantData::Unit(..) => false,
267 let discriminant_spans = variants.iter().filter(|variant| match variant.data {
268 VariantData::Tuple(..) | VariantData::Struct(..) => false,
269 VariantData::Unit(..) => true,
271 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
272 .collect::<Vec<_>>();
274 if !discriminant_spans.is_empty() && has_fields {
275 let mut err = feature_err(
277 sym::arbitrary_enum_discriminant,
278 discriminant_spans.clone(),
279 crate::feature_gate::GateIssue::Language,
280 "custom discriminant values are not allowed in enums with tuple or struct variants",
282 for sp in discriminant_spans {
283 err.span_label(sp, "disallowed custom discriminant");
285 for variant in variants.iter() {
286 match &variant.data {
287 VariantData::Struct(..) => {
290 "struct variant defined here",
293 VariantData::Tuple(..) => {
296 "tuple variant defined here",
299 VariantData::Unit(..) => {}
306 fn check_gat(&self, generics: &ast::Generics, span: Span) {
307 if !generics.params.is_empty() {
310 generic_associated_types,
312 "generic associated types are unstable"
315 if !generics.where_clause.predicates.is_empty() {
318 generic_associated_types,
320 "where clauses on associated types are unstable"
326 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
327 fn visit_attribute(&mut self, attr: &ast::Attribute) {
329 attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
330 // Check feature gates for built-in attributes.
331 if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
332 gate_feature_fn!(self, has_feature, attr.span, name, descr, GateStrength::Hard);
334 // Check input tokens for built-in and key-value attributes.
336 // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
337 Some((name, _, template, _)) if name != sym::rustc_dummy =>
338 check_builtin_attribute(self.parse_sess, attr, name, template),
339 _ => if let Some(TokenTree::Token(token)) =
340 attr.get_normal_item().tokens.trees().next() {
341 if token == token::Eq {
342 // All key-value attributes are restricted to meta-item syntax.
343 attr.parse_meta(self.parse_sess).map_err(|mut err| err.emit()).ok();
347 // Check unstable flavors of the `#[doc]` attribute.
348 if attr.check_name(sym::doc) {
349 for nested_meta in attr.meta_item_list().unwrap_or_default() {
350 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
351 $(if nested_meta.check_name(sym::$name) {
352 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
353 gate_feature!(self, $feature, attr.span, msg);
358 include => external_doc
361 spotlight => doc_spotlight
363 keyword => doc_keyword
369 fn visit_name(&mut self, sp: Span, name: ast::Name) {
370 if !name.as_str().is_ascii() {
374 self.parse_sess.source_map().def_span(sp),
375 "non-ascii idents are not fully supported"
380 fn visit_item(&mut self, i: &'a ast::Item) {
382 ast::ItemKind::ForeignMod(ref foreign_module) => {
383 self.check_abi(foreign_module.abi);
386 ast::ItemKind::Fn(..) => {
387 if attr::contains_name(&i.attrs[..], sym::plugin_registrar) {
388 gate_feature_post!(&self, plugin_registrar, i.span,
389 "compiler plugins are experimental and possibly buggy");
391 if attr::contains_name(&i.attrs[..], sym::start) {
392 gate_feature_post!(&self, start, i.span,
393 "a `#[start]` function is an experimental \
394 feature whose signature may change \
397 if attr::contains_name(&i.attrs[..], sym::main) {
398 gate_feature_post!(&self, main, i.span,
399 "declaration of a non-standard `#[main]` \
400 function may change over time, for now \
401 a top-level `fn main()` is required");
405 ast::ItemKind::Struct(..) => {
406 for attr in attr::filter_by_name(&i.attrs[..], sym::repr) {
407 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
408 if item.check_name(sym::simd) {
409 gate_feature_post!(&self, repr_simd, attr.span,
410 "SIMD types are experimental and possibly buggy");
416 ast::ItemKind::Enum(ast::EnumDef{ref variants, ..}, ..) => {
417 for variant in variants {
418 match (&variant.data, &variant.disr_expr) {
419 (ast::VariantData::Unit(..), _) => {},
420 (_, Some(disr_expr)) =>
423 arbitrary_enum_discriminant,
424 disr_expr.value.span,
425 "discriminants on non-unit variants are experimental"),
430 let has_feature = self.features.arbitrary_enum_discriminant;
431 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
432 self.maybe_report_invalid_custom_discriminants(&variants);
436 ast::ItemKind::Impl(_, polarity, defaultness, ..) => {
437 if polarity == ast::ImplPolarity::Negative {
438 gate_feature_post!(&self, optin_builtin_traits,
440 "negative trait bounds are not yet fully implemented; \
441 use marker types for now");
444 if let ast::Defaultness::Default = defaultness {
445 gate_feature_post!(&self, specialization,
447 "specialization is unstable");
451 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
452 gate_feature_post!(&self, optin_builtin_traits,
454 "auto traits are experimental and possibly buggy");
457 ast::ItemKind::TraitAlias(..) => {
462 "trait aliases are experimental"
466 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
467 let msg = "`macro` is experimental";
468 gate_feature_post!(&self, decl_macro, i.span, msg);
471 ast::ItemKind::OpaqueTy(..) => {
474 type_alias_impl_trait,
476 "`impl Trait` in type aliases is unstable"
483 visit::walk_item(self, i);
486 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
488 ast::ForeignItemKind::Fn(..) |
489 ast::ForeignItemKind::Static(..) => {
490 let link_name = attr::first_attr_value_str_by_name(&i.attrs, sym::link_name);
491 let links_to_llvm = match link_name {
492 Some(val) => val.as_str().starts_with("llvm."),
496 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
497 "linking to LLVM intrinsics is experimental");
500 ast::ForeignItemKind::Ty => {
501 gate_feature_post!(&self, extern_types, i.span,
502 "extern types are experimental");
504 ast::ForeignItemKind::Macro(..) => {}
507 visit::walk_foreign_item(self, i)
510 fn visit_ty(&mut self, ty: &'a ast::Ty) {
512 ast::TyKind::BareFn(ref bare_fn_ty) => {
513 self.check_abi(bare_fn_ty.abi);
515 ast::TyKind::Never => {
516 gate_feature_post!(&self, never_type, ty.span,
517 "The `!` type is experimental");
521 visit::walk_ty(self, ty)
524 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
525 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
526 if let ast::TyKind::Never = output_ty.kind {
529 self.visit_ty(output_ty)
534 fn visit_expr(&mut self, e: &'a ast::Expr) {
536 ast::ExprKind::Box(_) => {
537 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
539 ast::ExprKind::Type(..) => {
540 // To avoid noise about type ascription in common syntax errors, only emit if it
541 // is the *only* error.
542 if self.parse_sess.span_diagnostic.err_count() == 0 {
543 gate_feature_post!(&self, type_ascription, e.span,
544 "type ascription is experimental");
547 ast::ExprKind::TryBlock(_) => {
548 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
550 ast::ExprKind::Block(_, opt_label) => {
551 if let Some(label) = opt_label {
552 gate_feature_post!(&self, label_break_value, label.ident.span,
553 "labels on blocks are unstable");
558 visit::walk_expr(self, e)
561 fn visit_arm(&mut self, arm: &'a ast::Arm) {
562 visit::walk_arm(self, arm)
565 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
566 match &pattern.kind {
567 PatKind::Slice(pats) => {
570 let inner_pat = match &pat.kind {
571 PatKind::Ident(.., Some(pat)) => pat,
574 if inner_pat.is_rest() {
579 "subslice patterns are unstable"
584 PatKind::Box(..) => {
585 gate_feature_post!(&self, box_patterns,
587 "box pattern syntax is experimental");
589 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
590 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
591 "exclusive range pattern syntax is experimental");
595 visit::walk_pat(self, pattern)
598 fn visit_fn(&mut self,
600 fn_decl: &'a ast::FnDecl,
603 if let Some(header) = fn_kind.header() {
604 // Stability of const fn methods are covered in
605 // `visit_trait_item` and `visit_impl_item` below; this is
606 // because default methods don't pass through this point.
607 self.check_abi(header.abi);
610 if fn_decl.c_variadic() {
611 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
614 visit::walk_fn(self, fn_kind, fn_decl, span)
617 fn visit_generic_param(&mut self, param: &'a GenericParam) {
619 GenericParamKind::Const { .. } =>
620 gate_feature_post!(&self, const_generics, param.ident.span,
621 "const generics are unstable"),
624 visit::walk_generic_param(self, param)
627 fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
628 match constraint.kind {
629 AssocTyConstraintKind::Bound { .. } =>
630 gate_feature_post!(&self, associated_type_bounds, constraint.span,
631 "associated type bounds are unstable"),
634 visit::walk_assoc_ty_constraint(self, constraint)
637 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
639 ast::TraitItemKind::Method(ref sig, ref block) => {
641 self.check_abi(sig.header.abi);
643 if sig.decl.c_variadic() {
644 gate_feature_post!(&self, c_variadic, ti.span,
645 "C-variadic functions are unstable");
647 if sig.header.constness.node == ast::Constness::Const {
648 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
651 ast::TraitItemKind::Type(_, ref default) => {
652 // We use three if statements instead of something like match guards so that all
653 // of these errors can be emitted if all cases apply.
654 if default.is_some() {
655 gate_feature_post!(&self, associated_type_defaults, ti.span,
656 "associated type defaults are unstable");
658 self.check_gat(&ti.generics, ti.span);
662 visit::walk_trait_item(self, ti)
665 fn visit_impl_item(&mut self, ii: &'a ast::ImplItem) {
666 if ii.defaultness == ast::Defaultness::Default {
667 gate_feature_post!(&self, specialization,
669 "specialization is unstable");
673 ast::ImplItemKind::Method(ref sig, _) => {
674 if sig.decl.c_variadic() {
675 gate_feature_post!(&self, c_variadic, ii.span,
676 "C-variadic functions are unstable");
679 ast::ImplItemKind::OpaqueTy(..) => {
682 type_alias_impl_trait,
684 "`impl Trait` in type aliases is unstable"
687 ast::ImplItemKind::TyAlias(_) => {
688 self.check_gat(&ii.generics, ii.span);
692 visit::walk_impl_item(self, ii)
695 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
696 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
697 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
698 "`crate` visibility modifier is experimental");
700 visit::walk_vis(self, vis)
704 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
705 crate_edition: Edition, allow_features: &Option<Vec<String>>) -> Features {
706 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
707 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
708 if let Some(reason) = reason {
709 err.span_note(span, reason);
711 err.span_label(span, "feature has been removed");
716 let mut features = Features::new();
717 let mut edition_enabled_features = FxHashMap::default();
719 for &edition in ALL_EDITIONS {
720 if edition <= crate_edition {
721 // The `crate_edition` implies its respective umbrella feature-gate
722 // (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
723 edition_enabled_features.insert(edition.feature_name(), edition);
727 for feature in active_features_up_to(crate_edition) {
728 feature.set(&mut features, DUMMY_SP);
729 edition_enabled_features.insert(feature.name, crate_edition);
732 // Process the edition umbrella feature-gates first, to ensure
733 // `edition_enabled_features` is completed before it's queried.
734 for attr in krate_attrs {
735 if !attr.check_name(sym::feature) {
739 let list = match attr.meta_item_list() {
749 let name = mi.name_or_empty();
751 let edition = ALL_EDITIONS.iter().find(|e| name == e.feature_name()).copied();
752 if let Some(edition) = edition {
753 if edition <= crate_edition {
757 for feature in active_features_up_to(edition) {
758 // FIXME(Manishearth) there is currently no way to set
759 // lib features by edition
760 feature.set(&mut features, DUMMY_SP);
761 edition_enabled_features.insert(feature.name, edition);
767 for attr in krate_attrs {
768 if !attr.check_name(sym::feature) {
772 let list = match attr.meta_item_list() {
777 let bad_input = |span| {
778 struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
782 let name = match mi.ident() {
783 Some(ident) if mi.is_word() => ident.name,
785 bad_input(mi.span()).span_suggestion(
787 "expected just one word",
788 format!("{}", ident.name),
789 Applicability::MaybeIncorrect,
794 bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
799 if let Some(edition) = edition_enabled_features.get(&name) {
804 "the feature `{}` is included in the Rust {} edition",
811 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
812 // Handled in the separate loop above.
816 let removed = REMOVED_FEATURES.iter().find(|f| name == f.name);
817 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.name);
818 if let Some(Feature { state, .. }) = removed.or(stable_removed) {
819 if let FeatureState::Removed { reason }
820 | FeatureState::Stabilized { reason } = state
822 feature_removed(span_handler, mi.span(), *reason);
827 if let Some(Feature { since, .. }) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
828 let since = Some(Symbol::intern(since));
829 features.declared_lang_features.push((name, mi.span(), since));
833 if let Some(allowed) = allow_features.as_ref() {
834 if allowed.iter().find(|&f| name.as_str() == *f).is_none() {
835 span_err!(span_handler, mi.span(), E0725,
836 "the feature `{}` is not in the list of allowed features",
842 if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.name) {
843 f.set(&mut features, mi.span());
844 features.declared_lang_features.push((name, mi.span(), None));
848 features.declared_lib_features.push((name, mi.span()));
855 fn active_features_up_to(edition: Edition) -> impl Iterator<Item=&'static Feature> {
856 ACTIVE_FEATURES.iter()
857 .filter(move |feature| {
858 if let Some(feature_edition) = feature.edition {
859 feature_edition <= edition
866 pub fn check_crate(krate: &ast::Crate,
867 parse_sess: &ParseSess,
869 unstable: UnstableFeatures) {
870 maybe_stage_features(&parse_sess.span_diagnostic, krate, unstable);
871 let mut visitor = PostExpansionVisitor { parse_sess, features };
873 let spans = parse_sess.gated_spans.spans.borrow();
874 macro_rules! gate_all {
875 ($gate:ident, $msg:literal) => {
876 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
877 gate_feature!(&visitor, $gate, *span, $msg);
881 gate_all!(let_chains, "`let` expressions in this position are experimental");
882 gate_all!(async_closure, "async closures are unstable");
883 gate_all!(generators, "yield syntax is experimental");
884 gate_all!(or_patterns, "or-patterns syntax is experimental");
885 gate_all!(const_extern_fn, "`const extern fn` definitions are unstable");
887 // All uses of `gate_all!` below this point were added in #65742,
888 // and subsequently disabled (with the non-early gating readded).
889 macro_rules! gate_all {
890 ($gate:ident, $msg:literal) => {
891 // FIXME(eddyb) do something more useful than always
892 // disabling these uses of early feature-gatings.
894 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
895 gate_feature!(&visitor, $gate, *span, $msg);
901 gate_all!(trait_alias, "trait aliases are experimental");
902 gate_all!(associated_type_bounds, "associated type bounds are unstable");
903 gate_all!(crate_visibility_modifier, "`crate` visibility modifier is experimental");
904 gate_all!(const_generics, "const generics are unstable");
905 gate_all!(decl_macro, "`macro` is experimental");
906 gate_all!(box_patterns, "box pattern syntax is experimental");
907 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
908 gate_all!(try_blocks, "`try` blocks are unstable");
909 gate_all!(label_break_value, "labels on blocks are unstable");
910 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
911 // To avoid noise about type ascription in common syntax errors,
912 // only emit if it is the *only* error. (Also check it last.)
913 if parse_sess.span_diagnostic.err_count() == 0 {
914 gate_all!(type_ascription, "type ascription is experimental");
917 visit::walk_crate(&mut visitor, krate);
920 #[derive(Clone, Copy, Hash)]
921 pub enum UnstableFeatures {
922 /// Hard errors for unstable features are active, as on beta/stable channels.
924 /// Allow features to be activated, as on nightly.
926 /// Errors are bypassed for bootstrapping. This is required any time
927 /// during the build that feature-related lints are set to warn or above
928 /// because the build turns on warnings-as-errors and uses lots of unstable
929 /// features. As a result, this is always required for building Rust itself.
933 impl UnstableFeatures {
934 pub fn from_environment() -> UnstableFeatures {
935 // `true` if this is a feature-staged build, i.e., on the beta or stable channel.
936 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
937 // `true` if we should enable unstable features for bootstrapping.
938 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
939 match (disable_unstable_features, bootstrap) {
940 (_, true) => UnstableFeatures::Cheat,
941 (true, _) => UnstableFeatures::Disallow,
942 (false, _) => UnstableFeatures::Allow
946 pub fn is_nightly_build(&self) -> bool {
948 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
949 UnstableFeatures::Disallow => false,
954 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate, unstable: UnstableFeatures) {
955 if !unstable.is_nightly_build() {
956 for attr in krate.attrs.iter().filter(|attr| attr.check_name(sym::feature)) {
958 span_handler, attr.span, E0554,
959 "`#![feature]` may not be used on the {} release channel",
960 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")