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};
6 use crate::ast::{self, AssocTyConstraint, AssocTyConstraintKind, NodeId};
7 use crate::ast::{GenericParam, GenericParamKind, PatKind, RangeEnd, VariantData};
9 use crate::source_map::Spanned;
10 use crate::edition::{ALL_EDITIONS, Edition};
11 use crate::visit::{self, FnKind, Visitor};
12 use crate::sess::ParseSess;
13 use crate::symbol::{Symbol, sym};
15 use errors::{Applicability, DiagnosticBuilder, Handler};
16 use rustc_data_structures::fx::FxHashMap;
17 use syntax_pos::{Span, DUMMY_SP, MultiSpan};
20 use rustc_error_codes::*;
24 use std::num::NonZeroU32;
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<NonZeroU32> {
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
71 .chain(REMOVED_FEATURES)
72 .chain(STABLE_REMOVED_FEATURES)
73 .find(|t| t.name == feature);
75 Some(found) => found.issue(),
76 None => panic!("feature `{}` is not declared anywhere", feature),
83 Library(Option<NonZeroU32>)
86 #[derive(Debug, Copy, Clone, PartialEq)]
87 pub enum GateStrength {
88 /// A hard error. (Most feature gates should use this.)
90 /// Only a warning. (Use this only as backwards-compatibility demands.)
94 pub fn emit_feature_err(
101 feature_err(sess, feature, span, issue, explain).emit();
104 pub fn feature_err<'a, S: Into<MultiSpan>>(
110 ) -> DiagnosticBuilder<'a> {
111 leveled_feature_err(sess, feature, span, issue, explain, GateStrength::Hard)
114 fn leveled_feature_err<'a, S: Into<MultiSpan>>(
121 ) -> DiagnosticBuilder<'a> {
122 let diag = &sess.span_diagnostic;
124 let issue = match issue {
125 GateIssue::Language => find_lang_feature_issue(feature),
126 GateIssue::Library(lib) => lib,
129 let mut err = match level {
130 GateStrength::Hard => {
131 diag.struct_span_err_with_code(span, explain, stringify_error_code!(E0658))
133 GateStrength::Soft => diag.struct_span_warn(span, explain),
136 if let Some(n) = issue {
138 "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"
325 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
326 fn check_impl_trait(&self, ty: &ast::Ty) {
327 struct ImplTraitVisitor<'a> {
328 vis: &'a PostExpansionVisitor<'a>,
330 impl Visitor<'_> for ImplTraitVisitor<'_> {
331 fn visit_ty(&mut self, ty: &ast::Ty) {
332 if let ast::TyKind::ImplTrait(..) = ty.kind {
335 type_alias_impl_trait,
337 "`impl Trait` in type aliases is unstable"
340 visit::walk_ty(self, ty);
343 ImplTraitVisitor { vis: self }.visit_ty(ty);
347 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
348 fn visit_attribute(&mut self, attr: &ast::Attribute) {
350 attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
351 // Check feature gates for built-in attributes.
352 if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
353 gate_feature_fn!(self, has_feature, attr.span, name, descr, GateStrength::Hard);
355 // Check unstable flavors of the `#[doc]` attribute.
356 if attr.check_name(sym::doc) {
357 for nested_meta in attr.meta_item_list().unwrap_or_default() {
358 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
359 $(if nested_meta.check_name(sym::$name) {
360 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
361 gate_feature!(self, $feature, attr.span, msg);
366 include => external_doc
369 spotlight => doc_spotlight
371 keyword => doc_keyword
377 fn visit_name(&mut self, sp: Span, name: ast::Name) {
378 if !name.as_str().is_ascii() {
382 self.parse_sess.source_map().def_span(sp),
383 "non-ascii idents are not fully supported"
388 fn visit_item(&mut self, i: &'a ast::Item) {
390 ast::ItemKind::ForeignMod(ref foreign_module) => {
391 self.check_abi(foreign_module.abi);
394 ast::ItemKind::Fn(..) => {
395 if attr::contains_name(&i.attrs[..], sym::plugin_registrar) {
396 gate_feature_post!(&self, plugin_registrar, i.span,
397 "compiler plugins are experimental and possibly buggy");
399 if attr::contains_name(&i.attrs[..], sym::start) {
400 gate_feature_post!(&self, start, i.span,
401 "a `#[start]` function is an experimental \
402 feature whose signature may change \
405 if attr::contains_name(&i.attrs[..], sym::main) {
406 gate_feature_post!(&self, main, i.span,
407 "declaration of a non-standard `#[main]` \
408 function may change over time, for now \
409 a top-level `fn main()` is required");
413 ast::ItemKind::Struct(..) => {
414 for attr in attr::filter_by_name(&i.attrs[..], sym::repr) {
415 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
416 if item.check_name(sym::simd) {
417 gate_feature_post!(&self, repr_simd, attr.span,
418 "SIMD types are experimental and possibly buggy");
424 ast::ItemKind::Enum(ast::EnumDef{ref variants, ..}, ..) => {
425 for variant in variants {
426 match (&variant.data, &variant.disr_expr) {
427 (ast::VariantData::Unit(..), _) => {},
428 (_, Some(disr_expr)) =>
431 arbitrary_enum_discriminant,
432 disr_expr.value.span,
433 "discriminants on non-unit variants are experimental"),
438 let has_feature = self.features.arbitrary_enum_discriminant;
439 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
440 self.maybe_report_invalid_custom_discriminants(&variants);
444 ast::ItemKind::Impl(_, polarity, defaultness, ..) => {
445 if polarity == ast::ImplPolarity::Negative {
446 gate_feature_post!(&self, optin_builtin_traits,
448 "negative trait bounds are not yet fully implemented; \
449 use marker types for now");
452 if let ast::Defaultness::Default = defaultness {
453 gate_feature_post!(&self, specialization,
455 "specialization is unstable");
459 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
460 gate_feature_post!(&self, optin_builtin_traits,
462 "auto traits are experimental and possibly buggy");
465 ast::ItemKind::TraitAlias(..) => {
470 "trait aliases are experimental"
474 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
475 let msg = "`macro` is experimental";
476 gate_feature_post!(&self, decl_macro, i.span, msg);
479 ast::ItemKind::TyAlias(ref ty, ..) => self.check_impl_trait(&ty),
484 visit::walk_item(self, i);
487 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
489 ast::ForeignItemKind::Fn(..) |
490 ast::ForeignItemKind::Static(..) => {
491 let link_name = attr::first_attr_value_str_by_name(&i.attrs, sym::link_name);
492 let links_to_llvm = match link_name {
493 Some(val) => val.as_str().starts_with("llvm."),
497 gate_feature_post!(&self, link_llvm_intrinsics, i.span,
498 "linking to LLVM intrinsics is experimental");
501 ast::ForeignItemKind::Ty => {
502 gate_feature_post!(&self, extern_types, i.span,
503 "extern types are experimental");
505 ast::ForeignItemKind::Macro(..) => {}
508 visit::walk_foreign_item(self, i)
511 fn visit_ty(&mut self, ty: &'a ast::Ty) {
513 ast::TyKind::BareFn(ref bare_fn_ty) => {
514 self.check_abi(bare_fn_ty.abi);
516 ast::TyKind::Never => {
517 gate_feature_post!(&self, never_type, ty.span,
518 "The `!` type is experimental");
522 visit::walk_ty(self, ty)
525 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FunctionRetTy) {
526 if let ast::FunctionRetTy::Ty(ref output_ty) = *ret_ty {
527 if let ast::TyKind::Never = output_ty.kind {
530 self.visit_ty(output_ty)
535 fn visit_expr(&mut self, e: &'a ast::Expr) {
537 ast::ExprKind::Box(_) => {
538 gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
540 ast::ExprKind::Type(..) => {
541 // To avoid noise about type ascription in common syntax errors, only emit if it
542 // is the *only* error.
543 if self.parse_sess.span_diagnostic.err_count() == 0 {
544 gate_feature_post!(&self, type_ascription, e.span,
545 "type ascription is experimental");
548 ast::ExprKind::TryBlock(_) => {
549 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
551 ast::ExprKind::Block(_, opt_label) => {
552 if let Some(label) = opt_label {
553 gate_feature_post!(&self, label_break_value, label.ident.span,
554 "labels on blocks are unstable");
559 visit::walk_expr(self, e)
562 fn visit_arm(&mut self, arm: &'a ast::Arm) {
563 visit::walk_arm(self, arm)
566 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
567 match &pattern.kind {
568 PatKind::Slice(pats) => {
571 let inner_pat = match &pat.kind {
572 PatKind::Ident(.., Some(pat)) => pat,
575 if inner_pat.is_rest() {
580 "subslice patterns are unstable"
585 PatKind::Box(..) => {
586 gate_feature_post!(&self, box_patterns,
588 "box pattern syntax is experimental");
590 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
591 gate_feature_post!(&self, exclusive_range_pattern, pattern.span,
592 "exclusive range pattern syntax is experimental");
596 visit::walk_pat(self, pattern)
599 fn visit_fn(&mut self,
601 fn_decl: &'a ast::FnDecl,
604 if let Some(header) = fn_kind.header() {
605 // Stability of const fn methods are covered in
606 // `visit_trait_item` and `visit_impl_item` below; this is
607 // because default methods don't pass through this point.
608 self.check_abi(header.abi);
611 if fn_decl.c_variadic() {
612 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
615 visit::walk_fn(self, fn_kind, fn_decl, span)
618 fn visit_generic_param(&mut self, param: &'a GenericParam) {
620 GenericParamKind::Const { .. } =>
621 gate_feature_post!(&self, const_generics, param.ident.span,
622 "const generics are unstable"),
625 visit::walk_generic_param(self, param)
628 fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
629 match constraint.kind {
630 AssocTyConstraintKind::Bound { .. } =>
631 gate_feature_post!(&self, associated_type_bounds, constraint.span,
632 "associated type bounds are unstable"),
635 visit::walk_assoc_ty_constraint(self, constraint)
638 fn visit_trait_item(&mut self, ti: &'a ast::TraitItem) {
640 ast::TraitItemKind::Method(ref sig, ref block) => {
642 self.check_abi(sig.header.abi);
644 if sig.decl.c_variadic() {
645 gate_feature_post!(&self, c_variadic, ti.span,
646 "C-variadic functions are unstable");
648 if sig.header.constness.node == ast::Constness::Const {
649 gate_feature_post!(&self, const_fn, ti.span, "const fn is unstable");
652 ast::TraitItemKind::Type(_, ref default) => {
653 if let Some(ty) = default {
654 self.check_impl_trait(ty);
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::TyAlias(ref ty) => {
680 self.check_impl_trait(ty);
681 self.check_gat(&ii.generics, ii.span);
685 visit::walk_impl_item(self, ii)
688 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
689 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
690 gate_feature_post!(&self, crate_visibility_modifier, vis.span,
691 "`crate` visibility modifier is experimental");
693 visit::walk_vis(self, vis)
697 pub fn get_features(span_handler: &Handler, krate_attrs: &[ast::Attribute],
698 crate_edition: Edition, allow_features: &Option<Vec<String>>) -> Features {
699 fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
700 let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
701 if let Some(reason) = reason {
702 err.span_note(span, reason);
704 err.span_label(span, "feature has been removed");
709 let mut features = Features::new();
710 let mut edition_enabled_features = FxHashMap::default();
712 for &edition in ALL_EDITIONS {
713 if edition <= crate_edition {
714 // The `crate_edition` implies its respective umbrella feature-gate
715 // (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
716 edition_enabled_features.insert(edition.feature_name(), edition);
720 for feature in active_features_up_to(crate_edition) {
721 feature.set(&mut features, DUMMY_SP);
722 edition_enabled_features.insert(feature.name, crate_edition);
725 // Process the edition umbrella feature-gates first, to ensure
726 // `edition_enabled_features` is completed before it's queried.
727 for attr in krate_attrs {
728 if !attr.check_name(sym::feature) {
732 let list = match attr.meta_item_list() {
742 let name = mi.name_or_empty();
744 let edition = ALL_EDITIONS.iter().find(|e| name == e.feature_name()).copied();
745 if let Some(edition) = edition {
746 if edition <= crate_edition {
750 for feature in active_features_up_to(edition) {
751 // FIXME(Manishearth) there is currently no way to set
752 // lib features by edition
753 feature.set(&mut features, DUMMY_SP);
754 edition_enabled_features.insert(feature.name, edition);
760 for attr in krate_attrs {
761 if !attr.check_name(sym::feature) {
765 let list = match attr.meta_item_list() {
770 let bad_input = |span| {
771 struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
775 let name = match mi.ident() {
776 Some(ident) if mi.is_word() => ident.name,
778 bad_input(mi.span()).span_suggestion(
780 "expected just one word",
781 format!("{}", ident.name),
782 Applicability::MaybeIncorrect,
787 bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
792 if let Some(edition) = edition_enabled_features.get(&name) {
797 "the feature `{}` is included in the Rust {} edition",
804 if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
805 // Handled in the separate loop above.
809 let removed = REMOVED_FEATURES.iter().find(|f| name == f.name);
810 let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.name);
811 if let Some(Feature { state, .. }) = removed.or(stable_removed) {
812 if let FeatureState::Removed { reason }
813 | FeatureState::Stabilized { reason } = state
815 feature_removed(span_handler, mi.span(), *reason);
820 if let Some(Feature { since, .. }) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
821 let since = Some(Symbol::intern(since));
822 features.declared_lang_features.push((name, mi.span(), since));
826 if let Some(allowed) = allow_features.as_ref() {
827 if allowed.iter().find(|&f| name.as_str() == *f).is_none() {
828 span_err!(span_handler, mi.span(), E0725,
829 "the feature `{}` is not in the list of allowed features",
835 if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.name) {
836 f.set(&mut features, mi.span());
837 features.declared_lang_features.push((name, mi.span(), None));
841 features.declared_lib_features.push((name, mi.span()));
848 fn active_features_up_to(edition: Edition) -> impl Iterator<Item=&'static Feature> {
849 ACTIVE_FEATURES.iter()
850 .filter(move |feature| {
851 if let Some(feature_edition) = feature.edition {
852 feature_edition <= edition
859 pub fn check_crate(krate: &ast::Crate,
860 parse_sess: &ParseSess,
862 unstable: UnstableFeatures) {
863 maybe_stage_features(&parse_sess.span_diagnostic, krate, unstable);
864 let mut visitor = PostExpansionVisitor { parse_sess, features };
866 let spans = parse_sess.gated_spans.spans.borrow();
867 macro_rules! gate_all {
868 ($gate:ident, $msg:literal) => {
869 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
870 gate_feature!(&visitor, $gate, *span, $msg);
874 gate_all!(let_chains, "`let` expressions in this position are experimental");
875 gate_all!(async_closure, "async closures are unstable");
876 gate_all!(generators, "yield syntax is experimental");
877 gate_all!(or_patterns, "or-patterns syntax is experimental");
878 gate_all!(const_extern_fn, "`const extern fn` definitions are unstable");
880 // All uses of `gate_all!` below this point were added in #65742,
881 // and subsequently disabled (with the non-early gating readded).
882 macro_rules! gate_all {
883 ($gate:ident, $msg:literal) => {
884 // FIXME(eddyb) do something more useful than always
885 // disabling these uses of early feature-gatings.
887 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
888 gate_feature!(&visitor, $gate, *span, $msg);
894 gate_all!(trait_alias, "trait aliases are experimental");
895 gate_all!(associated_type_bounds, "associated type bounds are unstable");
896 gate_all!(crate_visibility_modifier, "`crate` visibility modifier is experimental");
897 gate_all!(const_generics, "const generics are unstable");
898 gate_all!(decl_macro, "`macro` is experimental");
899 gate_all!(box_patterns, "box pattern syntax is experimental");
900 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
901 gate_all!(try_blocks, "`try` blocks are unstable");
902 gate_all!(label_break_value, "labels on blocks are unstable");
903 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
904 // To avoid noise about type ascription in common syntax errors,
905 // only emit if it is the *only* error. (Also check it last.)
906 if parse_sess.span_diagnostic.err_count() == 0 {
907 gate_all!(type_ascription, "type ascription is experimental");
910 visit::walk_crate(&mut visitor, krate);
913 #[derive(Clone, Copy, Hash)]
914 pub enum UnstableFeatures {
915 /// Hard errors for unstable features are active, as on beta/stable channels.
917 /// Allow features to be activated, as on nightly.
919 /// Errors are bypassed for bootstrapping. This is required any time
920 /// during the build that feature-related lints are set to warn or above
921 /// because the build turns on warnings-as-errors and uses lots of unstable
922 /// features. As a result, this is always required for building Rust itself.
926 impl UnstableFeatures {
927 pub fn from_environment() -> UnstableFeatures {
928 // `true` if this is a feature-staged build, i.e., on the beta or stable channel.
929 let disable_unstable_features = option_env!("CFG_DISABLE_UNSTABLE_FEATURES").is_some();
930 // `true` if we should enable unstable features for bootstrapping.
931 let bootstrap = env::var("RUSTC_BOOTSTRAP").is_ok();
932 match (disable_unstable_features, bootstrap) {
933 (_, true) => UnstableFeatures::Cheat,
934 (true, _) => UnstableFeatures::Disallow,
935 (false, _) => UnstableFeatures::Allow
939 pub fn is_nightly_build(&self) -> bool {
941 UnstableFeatures::Allow | UnstableFeatures::Cheat => true,
942 UnstableFeatures::Disallow => false,
947 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate, unstable: UnstableFeatures) {
948 if !unstable.is_nightly_build() {
949 for attr in krate.attrs.iter().filter(|attr| attr.check_name(sym::feature)) {
951 span_handler, attr.span, E0554,
952 "`#![feature]` may not be used on the {} release channel",
953 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")