2 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
3 use rustc_ast::{AssocTyConstraint, AssocTyConstraintKind, NodeId};
4 use rustc_ast::{PatKind, RangeEnd, VariantData};
5 use rustc_errors::struct_span_err;
6 use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
7 use rustc_feature::{Features, GateIssue};
8 use rustc_session::parse::{feature_err, feature_err_issue};
9 use rustc_session::Session;
10 use rustc_span::source_map::Spanned;
11 use rustc_span::symbol::{sym, Symbol};
16 macro_rules! gate_feature_fn {
17 ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $help: expr) => {{
18 let (visitor, has_feature, span, name, explain, help) =
19 (&*$visitor, $has_feature, $span, $name, $explain, $help);
20 let has_feature: bool = has_feature(visitor.features);
21 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
22 if !has_feature && !span.allows_unstable($name) {
23 feature_err_issue(&visitor.sess.parse_sess, name, span, GateIssue::Language, explain)
28 ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
29 let (visitor, has_feature, span, name, explain) =
30 (&*$visitor, $has_feature, $span, $name, $explain);
31 let has_feature: bool = has_feature(visitor.features);
32 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
33 if !has_feature && !span.allows_unstable($name) {
34 feature_err_issue(&visitor.sess.parse_sess, name, span, GateIssue::Language, explain)
40 macro_rules! gate_feature_post {
41 ($visitor: expr, $feature: ident, $span: expr, $explain: expr, $help: expr) => {
42 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain, $help)
44 ($visitor: expr, $feature: ident, $span: expr, $explain: expr) => {
45 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain)
49 pub fn check_attribute(attr: &ast::Attribute, sess: &Session, features: &Features) {
50 PostExpansionVisitor { sess, features }.visit_attribute(attr)
53 struct PostExpansionVisitor<'a> {
56 // `sess` contains a `Features`, but this might not be that one.
57 features: &'a Features,
60 impl<'a> PostExpansionVisitor<'a> {
61 fn check_abi(&self, abi: ast::StrLit) {
62 let ast::StrLit { symbol_unescaped, span, .. } = abi;
64 match &*symbol_unescaped.as_str() {
66 "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
69 gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
71 "platform-intrinsic" => {
76 "platform intrinsics are experimental and possibly buggy"
84 "vectorcall is experimental and subject to change"
92 "thiscall is experimental and subject to change"
100 "rust-call ABI is subject to change"
108 "PTX ABIs are experimental and subject to change"
116 "unadjusted ABI is an implementation detail and perma-unstable"
119 "msp430-interrupt" => {
122 abi_msp430_interrupt,
124 "msp430-interrupt ABI is experimental and subject to change"
132 "x86-interrupt ABI is experimental and subject to change"
140 "amdgpu-kernel ABI is experimental and subject to change"
143 "avr-interrupt" | "avr-non-blocking-interrupt" => {
148 "avr-interrupt and avr-non-blocking-interrupt ABIs are experimental and subject to change"
156 "efiapi ABI is experimental and subject to change"
163 .delay_span_bug(span, &format!("unrecognized ABI not caught in lowering: {}", abi)),
167 fn check_extern(&self, ext: ast::Extern) {
168 if let ast::Extern::Explicit(abi) = ext {
173 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
174 let has_fields = variants.iter().any(|variant| match variant.data {
175 VariantData::Tuple(..) | VariantData::Struct(..) => true,
176 VariantData::Unit(..) => false,
179 let discriminant_spans = variants
181 .filter(|variant| match variant.data {
182 VariantData::Tuple(..) | VariantData::Struct(..) => false,
183 VariantData::Unit(..) => true,
185 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
186 .collect::<Vec<_>>();
188 if !discriminant_spans.is_empty() && has_fields {
189 let mut err = feature_err(
190 &self.sess.parse_sess,
191 sym::arbitrary_enum_discriminant,
192 discriminant_spans.clone(),
193 "custom discriminant values are not allowed in enums with tuple or struct variants",
195 for sp in discriminant_spans {
196 err.span_label(sp, "disallowed custom discriminant");
198 for variant in variants.iter() {
199 match &variant.data {
200 VariantData::Struct(..) => {
201 err.span_label(variant.span, "struct variant defined here");
203 VariantData::Tuple(..) => {
204 err.span_label(variant.span, "tuple variant defined here");
206 VariantData::Unit(..) => {}
213 fn check_gat(&self, generics: &ast::Generics, span: Span) {
214 if !generics.params.is_empty() {
217 generic_associated_types,
219 "generic associated types are unstable"
222 if !generics.where_clause.predicates.is_empty() {
225 generic_associated_types,
227 "where clauses on associated types are unstable"
232 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
233 fn check_impl_trait(&self, ty: &ast::Ty) {
234 struct ImplTraitVisitor<'a> {
235 vis: &'a PostExpansionVisitor<'a>,
237 impl Visitor<'_> for ImplTraitVisitor<'_> {
238 fn visit_ty(&mut self, ty: &ast::Ty) {
239 if let ast::TyKind::ImplTrait(..) = ty.kind {
242 type_alias_impl_trait,
244 "`impl Trait` in type aliases is unstable"
247 visit::walk_ty(self, ty);
250 ImplTraitVisitor { vis: self }.visit_ty(ty);
254 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
255 fn visit_attribute(&mut self, attr: &ast::Attribute) {
257 attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
258 // Check feature gates for built-in attributes.
259 if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
260 gate_feature_fn!(self, has_feature, attr.span, name, descr);
262 // Check unstable flavors of the `#[doc]` attribute.
263 if self.sess.check_name(attr, sym::doc) {
264 for nested_meta in attr.meta_item_list().unwrap_or_default() {
265 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
266 $(if nested_meta.has_name(sym::$name) {
267 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
268 gate_feature_post!(self, $feature, attr.span, msg);
273 include => external_doc
276 spotlight => doc_spotlight
277 keyword => doc_keyword
283 fn visit_name(&mut self, sp: Span, name: Symbol) {
284 if !name.as_str().is_ascii() {
288 self.sess.parse_sess.source_map().guess_head_span(sp),
289 "non-ascii idents are not fully supported"
294 fn visit_item(&mut self, i: &'a ast::Item) {
296 ast::ItemKind::ForeignMod(ref foreign_module) => {
297 if let Some(abi) = foreign_module.abi {
302 ast::ItemKind::Fn(..) => {
303 if self.sess.contains_name(&i.attrs[..], sym::plugin_registrar) {
308 "compiler plugins are experimental and possibly buggy"
311 if self.sess.contains_name(&i.attrs[..], sym::start) {
316 "`#[start]` functions are experimental \
317 and their signature may change \
321 if self.sess.contains_name(&i.attrs[..], sym::main) {
326 "declaration of a non-standard `#[main]` \
327 function may change over time, for now \
328 a top-level `fn main()` is required"
333 ast::ItemKind::Struct(..) => {
334 for attr in self.sess.filter_by_name(&i.attrs[..], sym::repr) {
335 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
336 if item.has_name(sym::simd) {
341 "SIMD types are experimental and possibly buggy"
348 ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
349 for variant in variants {
350 match (&variant.data, &variant.disr_expr) {
351 (ast::VariantData::Unit(..), _) => {}
352 (_, Some(disr_expr)) => gate_feature_post!(
354 arbitrary_enum_discriminant,
355 disr_expr.value.span,
356 "discriminants on non-unit variants are experimental"
362 let has_feature = self.features.arbitrary_enum_discriminant;
363 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
364 self.maybe_report_invalid_custom_discriminants(&variants);
368 ast::ItemKind::Impl { polarity, defaultness, ref of_trait, .. } => {
369 if let ast::ImplPolarity::Negative(span) = polarity {
373 span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(span)),
374 "negative trait bounds are not yet fully implemented; \
375 use marker types for now"
379 if let ast::Defaultness::Default(_) = defaultness {
380 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
384 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
389 "auto traits are experimental and possibly buggy"
393 ast::ItemKind::TraitAlias(..) => {
394 gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
397 ast::ItemKind::MacroDef(ast::MacroDef { macro_rules: false, .. }) => {
398 let msg = "`macro` is experimental";
399 gate_feature_post!(&self, decl_macro, i.span, msg);
402 ast::ItemKind::TyAlias(_, _, _, Some(ref ty)) => self.check_impl_trait(&ty),
407 visit::walk_item(self, i);
410 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
412 ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
413 let link_name = self.sess.first_attr_value_str_by_name(&i.attrs, sym::link_name);
415 link_name.map_or(false, |val| val.as_str().starts_with("llvm."));
419 link_llvm_intrinsics,
421 "linking to LLVM intrinsics is experimental"
425 ast::ForeignItemKind::TyAlias(..) => {
426 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
428 ast::ForeignItemKind::MacCall(..) => {}
431 visit::walk_foreign_item(self, i)
434 fn visit_ty(&mut self, ty: &'a ast::Ty) {
436 ast::TyKind::BareFn(ref bare_fn_ty) => {
437 self.check_extern(bare_fn_ty.ext);
439 ast::TyKind::Never => {
440 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
444 visit::walk_ty(self, ty)
447 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
448 if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
449 if let ast::TyKind::Never = output_ty.kind {
452 self.visit_ty(output_ty)
457 fn visit_expr(&mut self, e: &'a ast::Expr) {
459 ast::ExprKind::Box(_) => {
464 "box expression syntax is experimental; you can call `Box::new` instead"
467 ast::ExprKind::Type(..) => {
468 // To avoid noise about type ascription in common syntax errors, only emit if it
469 // is the *only* error.
470 if self.sess.parse_sess.span_diagnostic.err_count() == 0 {
475 "type ascription is experimental"
479 ast::ExprKind::TryBlock(_) => {
480 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
482 ast::ExprKind::Block(_, opt_label) => {
483 if let Some(label) = opt_label {
488 "labels on blocks are unstable"
494 visit::walk_expr(self, e)
497 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
498 match &pattern.kind {
499 PatKind::Box(..) => {
504 "box pattern syntax is experimental"
507 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
510 exclusive_range_pattern,
512 "exclusive range pattern syntax is experimental"
517 visit::walk_pat(self, pattern)
520 fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
521 if let Some(header) = fn_kind.header() {
522 // Stability of const fn methods are covered in `visit_assoc_item` below.
523 self.check_extern(header.ext);
525 if let (ast::Const::Yes(_), ast::Extern::Implicit)
526 | (ast::Const::Yes(_), ast::Extern::Explicit(_)) = (header.constness, header.ext)
532 "`const extern fn` definitions are unstable"
537 if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
538 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
541 visit::walk_fn(self, fn_kind, span)
544 fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
545 if let AssocTyConstraintKind::Bound { .. } = constraint.kind {
548 associated_type_bounds,
550 "associated type bounds are unstable"
553 visit::walk_assoc_ty_constraint(self, constraint)
556 fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
557 let is_fn = match i.kind {
558 ast::AssocItemKind::Fn(_, ref sig, _, _) => {
559 if let (ast::Const::Yes(_), AssocCtxt::Trait) = (sig.header.constness, ctxt) {
560 gate_feature_post!(&self, const_fn, i.span, "const fn is unstable");
564 ast::AssocItemKind::TyAlias(_, ref generics, _, ref ty) => {
565 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
568 associated_type_defaults,
570 "associated type defaults are unstable"
573 if let Some(ty) = ty {
574 self.check_impl_trait(ty);
576 self.check_gat(generics, i.span);
581 if let ast::Defaultness::Default(_) = i.kind.defaultness() {
582 // Limit `min_specialization` to only specializing functions.
585 |x: &Features| x.specialization || (is_fn && x.min_specialization),
588 "specialization is unstable"
591 visit::walk_assoc_item(self, i, ctxt)
594 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
595 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.kind {
598 crate_visibility_modifier,
600 "`crate` visibility modifier is experimental"
603 visit::walk_vis(self, vis)
607 pub fn check_crate(krate: &ast::Crate, sess: &Session) {
608 maybe_stage_features(sess, krate);
609 check_incompatible_features(sess);
610 let mut visitor = PostExpansionVisitor { sess, features: &sess.features_untracked() };
612 let spans = sess.parse_sess.gated_spans.spans.borrow();
613 macro_rules! gate_all {
614 ($gate:ident, $msg:literal, $help:literal) => {
615 if let Some(spans) = spans.get(&sym::$gate) {
617 gate_feature_post!(&visitor, $gate, *span, $msg, $help);
621 ($gate:ident, $msg:literal) => {
622 if let Some(spans) = spans.get(&sym::$gate) {
624 gate_feature_post!(&visitor, $gate, *span, $msg);
629 gate_all!(if_let_guard, "`if let` guards are experimental");
630 gate_all!(let_chains, "`let` expressions in this position are experimental");
633 "async closures are unstable",
634 "to use an async block, remove the `||`: `async {`"
636 gate_all!(generators, "yield syntax is experimental");
637 gate_all!(or_patterns, "or-patterns syntax is experimental");
638 gate_all!(raw_ref_op, "raw address of syntax is experimental");
639 gate_all!(const_trait_bound_opt_out, "`?const` on trait bounds is experimental");
640 gate_all!(const_trait_impl, "const trait impls are experimental");
641 gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
642 gate_all!(inline_const, "inline-const is experimental");
644 extended_key_value_attributes,
645 "arbitrary expressions in key-value attributes are unstable"
648 const_generics_defaults,
649 "default values for const generic parameters are experimental"
651 if sess.parse_sess.span_diagnostic.err_count() == 0 {
652 // Errors for `destructuring_assignment` can get quite noisy, especially where `_` is
653 // involved, so we only emit errors where there are no other parsing errors.
654 gate_all!(destructuring_assignment, "destructuring assignments are unstable");
657 // All uses of `gate_all!` below this point were added in #65742,
658 // and subsequently disabled (with the non-early gating readded).
659 macro_rules! gate_all {
660 ($gate:ident, $msg:literal) => {
661 // FIXME(eddyb) do something more useful than always
662 // disabling these uses of early feature-gatings.
664 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
665 gate_feature_post!(&visitor, $gate, *span, $msg);
671 gate_all!(trait_alias, "trait aliases are experimental");
672 gate_all!(associated_type_bounds, "associated type bounds are unstable");
673 gate_all!(crate_visibility_modifier, "`crate` visibility modifier is experimental");
674 gate_all!(const_generics, "const generics are unstable");
675 gate_all!(decl_macro, "`macro` is experimental");
676 gate_all!(box_patterns, "box pattern syntax is experimental");
677 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
678 gate_all!(try_blocks, "`try` blocks are unstable");
679 gate_all!(label_break_value, "labels on blocks are unstable");
680 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
681 // To avoid noise about type ascription in common syntax errors,
682 // only emit if it is the *only* error. (Also check it last.)
683 if sess.parse_sess.span_diagnostic.err_count() == 0 {
684 gate_all!(type_ascription, "type ascription is experimental");
687 visit::walk_crate(&mut visitor, krate);
690 fn maybe_stage_features(sess: &Session, krate: &ast::Crate) {
691 if !sess.opts.unstable_features.is_nightly_build() {
692 for attr in krate.attrs.iter().filter(|attr| sess.check_name(attr, sym::feature)) {
694 sess.parse_sess.span_diagnostic,
697 "`#![feature]` may not be used on the {} release channel",
698 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")
705 fn check_incompatible_features(sess: &Session) {
706 let features = sess.features_untracked();
708 let declared_features = features
709 .declared_lang_features
712 .map(|(name, span, _)| (name, span))
713 .chain(features.declared_lib_features.iter().copied());
715 for (f1, f2) in rustc_feature::INCOMPATIBLE_FEATURES
717 .filter(|&&(f1, f2)| features.enabled(f1) && features.enabled(f2))
719 if let Some((f1_name, f1_span)) = declared_features.clone().find(|(name, _)| name == f1) {
720 if let Some((f2_name, f2_span)) = declared_features.clone().find(|(name, _)| name == f2)
722 let spans = vec![f1_span, f2_span];
723 sess.struct_span_err(
726 "features `{}` and `{}` are incompatible, using them at the same time \
731 .help("remove one of these features")