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, $explain: expr) => {{
18 let (visitor, has_feature, span, name, explain) =
19 (&*$visitor, $has_feature, $span, $name, $explain);
20 let has_feature: bool = has_feature(visitor.features);
21 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
22 if !has_feature && !span.allows_unstable($name) {
23 feature_err_issue(&visitor.sess.parse_sess, name, span, GateIssue::Language, explain)
29 macro_rules! gate_feature_post {
30 ($visitor: expr, $feature: ident, $span: expr, $explain: expr) => {
31 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain)
35 pub fn check_attribute(attr: &ast::Attribute, sess: &Session, features: &Features) {
36 PostExpansionVisitor { sess, features }.visit_attribute(attr)
39 struct PostExpansionVisitor<'a> {
42 // `sess` contains a `Features`, but this might not be that one.
43 features: &'a Features,
46 impl<'a> PostExpansionVisitor<'a> {
47 fn check_abi(&self, abi: ast::StrLit) {
48 let ast::StrLit { symbol_unescaped, span, .. } = abi;
50 match &*symbol_unescaped.as_str() {
52 "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
55 gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
57 "platform-intrinsic" => {
62 "platform intrinsics are experimental and possibly buggy"
70 "vectorcall is experimental and subject to change"
78 "thiscall is experimental and subject to change"
86 "rust-call ABI is subject to change"
94 "PTX ABIs are experimental and subject to change"
102 "unadjusted ABI is an implementation detail and perma-unstable"
105 "msp430-interrupt" => {
108 abi_msp430_interrupt,
110 "msp430-interrupt ABI is experimental and subject to change"
118 "x86-interrupt ABI is experimental and subject to change"
126 "amdgpu-kernel ABI is experimental and subject to change"
129 "avr-interrupt" | "avr-non-blocking-interrupt" => {
134 "avr-interrupt and avr-non-blocking-interrupt ABIs are experimental and subject to change"
142 "efiapi ABI is experimental and subject to change"
149 .delay_span_bug(span, &format!("unrecognized ABI not caught in lowering: {}", abi)),
153 fn check_extern(&self, ext: ast::Extern) {
154 if let ast::Extern::Explicit(abi) = ext {
159 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
160 let has_fields = variants.iter().any(|variant| match variant.data {
161 VariantData::Tuple(..) | VariantData::Struct(..) => true,
162 VariantData::Unit(..) => false,
165 let discriminant_spans = variants
167 .filter(|variant| match variant.data {
168 VariantData::Tuple(..) | VariantData::Struct(..) => false,
169 VariantData::Unit(..) => true,
171 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
172 .collect::<Vec<_>>();
174 if !discriminant_spans.is_empty() && has_fields {
175 let mut err = feature_err(
176 &self.sess.parse_sess,
177 sym::arbitrary_enum_discriminant,
178 discriminant_spans.clone(),
179 "custom discriminant values are not allowed in enums with tuple or struct variants",
181 for sp in discriminant_spans {
182 err.span_label(sp, "disallowed custom discriminant");
184 for variant in variants.iter() {
185 match &variant.data {
186 VariantData::Struct(..) => {
187 err.span_label(variant.span, "struct variant defined here");
189 VariantData::Tuple(..) => {
190 err.span_label(variant.span, "tuple variant defined here");
192 VariantData::Unit(..) => {}
199 fn check_gat(&self, generics: &ast::Generics, span: Span) {
200 if !generics.params.is_empty() {
203 generic_associated_types,
205 "generic associated types are unstable"
208 if !generics.where_clause.predicates.is_empty() {
211 generic_associated_types,
213 "where clauses on associated types are unstable"
218 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
219 fn check_impl_trait(&self, ty: &ast::Ty) {
220 struct ImplTraitVisitor<'a> {
221 vis: &'a PostExpansionVisitor<'a>,
223 impl Visitor<'_> for ImplTraitVisitor<'_> {
224 fn visit_ty(&mut self, ty: &ast::Ty) {
225 if let ast::TyKind::ImplTrait(..) = ty.kind {
228 type_alias_impl_trait,
230 "`impl Trait` in type aliases is unstable"
233 visit::walk_ty(self, ty);
236 ImplTraitVisitor { vis: self }.visit_ty(ty);
240 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
241 fn visit_attribute(&mut self, attr: &ast::Attribute) {
243 attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
244 // Check feature gates for built-in attributes.
245 if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
246 gate_feature_fn!(self, has_feature, attr.span, name, descr);
248 // Check unstable flavors of the `#[doc]` attribute.
249 if self.sess.check_name(attr, sym::doc) {
250 for nested_meta in attr.meta_item_list().unwrap_or_default() {
251 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
252 $(if nested_meta.has_name(sym::$name) {
253 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
254 gate_feature_post!(self, $feature, attr.span, msg);
259 include => external_doc
262 spotlight => doc_spotlight
263 keyword => doc_keyword
269 fn visit_name(&mut self, sp: Span, name: Symbol) {
270 if !name.as_str().is_ascii() {
274 self.sess.parse_sess.source_map().guess_head_span(sp),
275 "non-ascii idents are not fully supported"
280 fn visit_item(&mut self, i: &'a ast::Item) {
282 ast::ItemKind::ForeignMod(ref foreign_module) => {
283 if let Some(abi) = foreign_module.abi {
288 ast::ItemKind::Fn(..) => {
289 if self.sess.contains_name(&i.attrs[..], sym::plugin_registrar) {
294 "compiler plugins are experimental and possibly buggy"
297 if self.sess.contains_name(&i.attrs[..], sym::start) {
302 "`#[start]` functions are experimental \
303 and their signature may change \
307 if self.sess.contains_name(&i.attrs[..], sym::main) {
312 "declaration of a non-standard `#[main]` \
313 function may change over time, for now \
314 a top-level `fn main()` is required"
319 ast::ItemKind::Struct(..) => {
320 for attr in self.sess.filter_by_name(&i.attrs[..], sym::repr) {
321 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
322 if item.has_name(sym::simd) {
327 "SIMD types are experimental and possibly buggy"
334 ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
335 for variant in variants {
336 match (&variant.data, &variant.disr_expr) {
337 (ast::VariantData::Unit(..), _) => {}
338 (_, Some(disr_expr)) => gate_feature_post!(
340 arbitrary_enum_discriminant,
341 disr_expr.value.span,
342 "discriminants on non-unit variants are experimental"
348 let has_feature = self.features.arbitrary_enum_discriminant;
349 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
350 self.maybe_report_invalid_custom_discriminants(&variants);
354 ast::ItemKind::Impl { polarity, defaultness, ref of_trait, .. } => {
355 if let ast::ImplPolarity::Negative(span) = polarity {
359 span.to(of_trait.as_ref().map(|t| t.path.span).unwrap_or(span)),
360 "negative trait bounds are not yet fully implemented; \
361 use marker types for now"
365 if let ast::Defaultness::Default(_) = defaultness {
366 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
370 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
375 "auto traits are experimental and possibly buggy"
379 ast::ItemKind::TraitAlias(..) => {
380 gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
383 ast::ItemKind::MacroDef(ast::MacroDef { macro_rules: false, .. }) => {
384 let msg = "`macro` is experimental";
385 gate_feature_post!(&self, decl_macro, i.span, msg);
388 ast::ItemKind::TyAlias(_, _, _, Some(ref ty)) => self.check_impl_trait(&ty),
393 visit::walk_item(self, i);
396 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
398 ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
399 let link_name = self.sess.first_attr_value_str_by_name(&i.attrs, sym::link_name);
401 link_name.map_or(false, |val| val.as_str().starts_with("llvm."));
405 link_llvm_intrinsics,
407 "linking to LLVM intrinsics is experimental"
411 ast::ForeignItemKind::TyAlias(..) => {
412 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
414 ast::ForeignItemKind::MacCall(..) => {}
417 visit::walk_foreign_item(self, i)
420 fn visit_ty(&mut self, ty: &'a ast::Ty) {
422 ast::TyKind::BareFn(ref bare_fn_ty) => {
423 self.check_extern(bare_fn_ty.ext);
425 ast::TyKind::Never => {
426 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
430 visit::walk_ty(self, ty)
433 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
434 if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
435 if let ast::TyKind::Never = output_ty.kind {
438 self.visit_ty(output_ty)
443 fn visit_expr(&mut self, e: &'a ast::Expr) {
445 ast::ExprKind::Box(_) => {
450 "box expression syntax is experimental; you can call `Box::new` instead"
453 ast::ExprKind::Type(..) => {
454 // To avoid noise about type ascription in common syntax errors, only emit if it
455 // is the *only* error.
456 if self.sess.parse_sess.span_diagnostic.err_count() == 0 {
461 "type ascription is experimental"
465 ast::ExprKind::TryBlock(_) => {
466 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
468 ast::ExprKind::Block(_, opt_label) => {
469 if let Some(label) = opt_label {
474 "labels on blocks are unstable"
480 visit::walk_expr(self, e)
483 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
484 match &pattern.kind {
485 PatKind::Box(..) => {
490 "box pattern syntax is experimental"
493 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
496 exclusive_range_pattern,
498 "exclusive range pattern syntax is experimental"
503 visit::walk_pat(self, pattern)
506 fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
507 if let Some(header) = fn_kind.header() {
508 // Stability of const fn methods are covered in `visit_assoc_item` below.
509 self.check_extern(header.ext);
511 if let (ast::Const::Yes(_), ast::Extern::Implicit)
512 | (ast::Const::Yes(_), ast::Extern::Explicit(_)) = (header.constness, header.ext)
518 "`const extern fn` definitions are unstable"
523 if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
524 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
527 visit::walk_fn(self, fn_kind, span)
530 fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
531 if let AssocTyConstraintKind::Bound { .. } = constraint.kind {
534 associated_type_bounds,
536 "associated type bounds are unstable"
539 visit::walk_assoc_ty_constraint(self, constraint)
542 fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
543 let is_fn = match i.kind {
544 ast::AssocItemKind::Fn(_, ref sig, _, _) => {
545 if let (ast::Const::Yes(_), AssocCtxt::Trait) = (sig.header.constness, ctxt) {
546 gate_feature_post!(&self, const_fn, i.span, "const fn is unstable");
550 ast::AssocItemKind::TyAlias(_, ref generics, _, ref ty) => {
551 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
554 associated_type_defaults,
556 "associated type defaults are unstable"
559 if let Some(ty) = ty {
560 self.check_impl_trait(ty);
562 self.check_gat(generics, i.span);
567 if let ast::Defaultness::Default(_) = i.kind.defaultness() {
568 // Limit `min_specialization` to only specializing functions.
571 |x: &Features| x.specialization || (is_fn && x.min_specialization),
574 "specialization is unstable"
577 visit::walk_assoc_item(self, i, ctxt)
580 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
581 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.kind {
584 crate_visibility_modifier,
586 "`crate` visibility modifier is experimental"
589 visit::walk_vis(self, vis)
593 pub fn check_crate(krate: &ast::Crate, sess: &Session) {
594 maybe_stage_features(sess, krate);
595 check_incompatible_features(sess);
596 let mut visitor = PostExpansionVisitor { sess, features: &sess.features_untracked() };
598 let spans = sess.parse_sess.gated_spans.spans.borrow();
599 macro_rules! gate_all {
600 ($gate:ident, $msg:literal) => {
601 if let Some(spans) = spans.get(&sym::$gate) {
603 gate_feature_post!(&visitor, $gate, *span, $msg);
608 gate_all!(if_let_guard, "`if let` guards are experimental");
609 gate_all!(let_chains, "`let` expressions in this position are experimental");
610 gate_all!(async_closure, "async closures are unstable");
611 gate_all!(generators, "yield syntax is experimental");
612 gate_all!(or_patterns, "or-patterns syntax is experimental");
613 gate_all!(raw_ref_op, "raw address of syntax is experimental");
614 gate_all!(const_trait_bound_opt_out, "`?const` on trait bounds is experimental");
615 gate_all!(const_trait_impl, "const trait impls are experimental");
616 gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
617 gate_all!(inline_const, "inline-const is experimental");
619 extended_key_value_attributes,
620 "arbitrary expressions in key-value attributes are unstable"
622 if sess.parse_sess.span_diagnostic.err_count() == 0 {
623 // Errors for `destructuring_assignment` can get quite noisy, especially where `_` is
624 // involved, so we only emit errors where there are no other parsing errors.
625 gate_all!(destructuring_assignment, "destructuring assignments are unstable");
628 // All uses of `gate_all!` below this point were added in #65742,
629 // and subsequently disabled (with the non-early gating readded).
630 macro_rules! gate_all {
631 ($gate:ident, $msg:literal) => {
632 // FIXME(eddyb) do something more useful than always
633 // disabling these uses of early feature-gatings.
635 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
636 gate_feature_post!(&visitor, $gate, *span, $msg);
642 gate_all!(trait_alias, "trait aliases are experimental");
643 gate_all!(associated_type_bounds, "associated type bounds are unstable");
644 gate_all!(crate_visibility_modifier, "`crate` visibility modifier is experimental");
645 gate_all!(const_generics, "const generics are unstable");
646 gate_all!(decl_macro, "`macro` is experimental");
647 gate_all!(box_patterns, "box pattern syntax is experimental");
648 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
649 gate_all!(try_blocks, "`try` blocks are unstable");
650 gate_all!(label_break_value, "labels on blocks are unstable");
651 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
652 // To avoid noise about type ascription in common syntax errors,
653 // only emit if it is the *only* error. (Also check it last.)
654 if sess.parse_sess.span_diagnostic.err_count() == 0 {
655 gate_all!(type_ascription, "type ascription is experimental");
658 visit::walk_crate(&mut visitor, krate);
661 fn maybe_stage_features(sess: &Session, krate: &ast::Crate) {
662 if !sess.opts.unstable_features.is_nightly_build() {
663 for attr in krate.attrs.iter().filter(|attr| sess.check_name(attr, sym::feature)) {
665 sess.parse_sess.span_diagnostic,
668 "`#![feature]` may not be used on the {} release channel",
669 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")
676 fn check_incompatible_features(sess: &Session) {
677 let features = sess.features_untracked();
679 let declared_features = features
680 .declared_lang_features
683 .map(|(name, span, _)| (name, span))
684 .chain(features.declared_lib_features.iter().copied());
686 for (f1, f2) in rustc_feature::INCOMPATIBLE_FEATURES
688 .filter(|&&(f1, f2)| features.enabled(f1) && features.enabled(f2))
690 if let Some((f1_name, f1_span)) = declared_features.clone().find(|(name, _)| name == f1) {
691 if let Some((f2_name, f2_span)) = declared_features.clone().find(|(name, _)| name == f2)
693 let spans = vec![f1_span, f2_span];
694 sess.struct_span_err(
697 "features `{}` and `{}` are incompatible, using them at the same time \
702 .help("remove one of these features")