2 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
3 use rustc_ast::{AssocConstraint, AssocConstraintKind, NodeId};
4 use rustc_ast::{PatKind, RangeEnd, VariantData};
5 use rustc_errors::struct_span_err;
6 use rustc_feature::{AttributeGate, BuiltinAttribute, 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;
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, constness: ast::Const) {
62 let ast::StrLit { symbol_unescaped, span, .. } = abi;
64 if let ast::Const::Yes(_) = constness {
65 match symbol_unescaped.as_str() {
68 abi => gate_feature_post!(
72 &format!("`{}` as a `const fn` ABI is unstable", abi)
77 match symbol_unescaped.as_str() {
79 "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
82 gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
84 "platform-intrinsic" => {
89 "platform intrinsics are experimental and possibly buggy"
97 "vectorcall is experimental and subject to change"
105 "thiscall is experimental and subject to change"
113 "rust-call ABI is subject to change"
121 "rust-cold is experimental and subject to change"
129 "PTX ABIs are experimental and subject to change"
137 "unadjusted ABI is an implementation detail and perma-unstable"
140 "msp430-interrupt" => {
143 abi_msp430_interrupt,
145 "msp430-interrupt ABI is experimental and subject to change"
153 "x86-interrupt ABI is experimental and subject to change"
161 "amdgpu-kernel ABI is experimental and subject to change"
164 "avr-interrupt" | "avr-non-blocking-interrupt" => {
169 "avr-interrupt and avr-non-blocking-interrupt ABIs are experimental and subject to change"
177 "efiapi ABI is experimental and subject to change"
180 "C-cmse-nonsecure-call" => {
183 abi_c_cmse_nonsecure_call,
185 "C-cmse-nonsecure-call ABI is experimental and subject to change"
193 "C-unwind ABI is experimental and subject to change"
196 "stdcall-unwind" => {
201 "stdcall-unwind ABI is experimental and subject to change"
209 "system-unwind ABI is experimental and subject to change"
212 "thiscall-unwind" => {
217 "thiscall-unwind ABI is experimental and subject to change"
225 "cdecl-unwind ABI is experimental and subject to change"
228 "fastcall-unwind" => {
233 "fastcall-unwind ABI is experimental and subject to change"
236 "vectorcall-unwind" => {
241 "vectorcall-unwind ABI is experimental and subject to change"
249 "aapcs-unwind ABI is experimental and subject to change"
257 "win64-unwind ABI is experimental and subject to change"
265 "sysv64-unwind ABI is experimental and subject to change"
273 "wasm ABI is experimental and subject to change"
277 self.sess.parse_sess.span_diagnostic.delay_span_bug(
279 &format!("unrecognized ABI not caught in lowering: {}", abi),
285 fn check_extern(&self, ext: ast::Extern, constness: ast::Const) {
286 if let ast::Extern::Explicit(abi, _) = ext {
287 self.check_abi(abi, constness);
291 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
292 let has_fields = variants.iter().any(|variant| match variant.data {
293 VariantData::Tuple(..) | VariantData::Struct(..) => true,
294 VariantData::Unit(..) => false,
297 let discriminant_spans = variants
299 .filter(|variant| match variant.data {
300 VariantData::Tuple(..) | VariantData::Struct(..) => false,
301 VariantData::Unit(..) => true,
303 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
304 .collect::<Vec<_>>();
306 if !discriminant_spans.is_empty() && has_fields {
307 let mut err = feature_err(
308 &self.sess.parse_sess,
309 sym::arbitrary_enum_discriminant,
310 discriminant_spans.clone(),
311 "custom discriminant values are not allowed in enums with tuple or struct variants",
313 for sp in discriminant_spans {
314 err.span_label(sp, "disallowed custom discriminant");
316 for variant in variants.iter() {
317 match &variant.data {
318 VariantData::Struct(..) => {
319 err.span_label(variant.span, "struct variant defined here");
321 VariantData::Tuple(..) => {
322 err.span_label(variant.span, "tuple variant defined here");
324 VariantData::Unit(..) => {}
331 fn check_gat(&self, generics: &ast::Generics, span: Span) {
332 if !generics.params.is_empty() {
335 generic_associated_types,
337 "generic associated types are unstable"
340 if !generics.where_clause.predicates.is_empty() {
343 generic_associated_types,
345 "where clauses on associated types are unstable"
350 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
351 fn check_impl_trait(&self, ty: &ast::Ty) {
352 struct ImplTraitVisitor<'a> {
353 vis: &'a PostExpansionVisitor<'a>,
355 impl Visitor<'_> for ImplTraitVisitor<'_> {
356 fn visit_ty(&mut self, ty: &ast::Ty) {
357 if let ast::TyKind::ImplTrait(..) = ty.kind {
360 type_alias_impl_trait,
362 "`impl Trait` in type aliases is unstable"
365 visit::walk_ty(self, ty);
368 ImplTraitVisitor { vis: self }.visit_ty(ty);
372 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
373 fn visit_attribute(&mut self, attr: &ast::Attribute) {
374 let attr_info = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
375 // Check feature gates for built-in attributes.
376 if let Some(BuiltinAttribute {
377 gate: AttributeGate::Gated(_, name, descr, has_feature),
381 gate_feature_fn!(self, has_feature, attr.span, *name, descr);
383 // Check unstable flavors of the `#[doc]` attribute.
384 if attr.has_name(sym::doc) {
385 for nested_meta in attr.meta_item_list().unwrap_or_default() {
386 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
387 $(if nested_meta.has_name(sym::$name) {
388 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
389 gate_feature_post!(self, $feature, attr.span, msg);
395 cfg_hide => doc_cfg_hide
397 notable_trait => doc_notable_trait
400 if nested_meta.has_name(sym::keyword) {
401 let msg = "`#[doc(keyword)]` is meant for internal use only";
402 gate_feature_post!(self, rustdoc_internals, attr.span, msg);
405 if nested_meta.has_name(sym::tuple_variadic) {
406 let msg = "`#[doc(tuple_variadic)]` is meant for internal use only";
407 gate_feature_post!(self, rustdoc_internals, attr.span, msg);
412 // Emit errors for non-staged-api crates.
413 if !self.features.staged_api {
414 if attr.has_name(sym::unstable)
415 || attr.has_name(sym::stable)
416 || attr.has_name(sym::rustc_const_unstable)
417 || attr.has_name(sym::rustc_const_stable)
423 "stability attributes may not be used outside of the standard library",
430 fn visit_item(&mut self, i: &'a ast::Item) {
432 ast::ItemKind::ForeignMod(ref foreign_module) => {
433 if let Some(abi) = foreign_module.abi {
434 self.check_abi(abi, ast::Const::No);
438 ast::ItemKind::Fn(..) => {
439 if self.sess.contains_name(&i.attrs, sym::start) {
444 "`#[start]` functions are experimental \
445 and their signature may change \
451 ast::ItemKind::Struct(..) => {
452 for attr in self.sess.filter_by_name(&i.attrs, sym::repr) {
453 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
454 if item.has_name(sym::simd) {
459 "SIMD types are experimental and possibly buggy"
466 ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
467 for variant in variants {
468 match (&variant.data, &variant.disr_expr) {
469 (ast::VariantData::Unit(..), _) => {}
470 (_, Some(disr_expr)) => gate_feature_post!(
472 arbitrary_enum_discriminant,
473 disr_expr.value.span,
474 "discriminants on non-unit variants are experimental"
480 let has_feature = self.features.arbitrary_enum_discriminant;
481 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
482 self.maybe_report_invalid_custom_discriminants(&variants);
486 ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, ref of_trait, .. }) => {
487 if let ast::ImplPolarity::Negative(span) = polarity {
491 span.to(of_trait.as_ref().map_or(span, |t| t.path.span)),
492 "negative trait bounds are not yet fully implemented; \
493 use marker types for now"
497 if let ast::Defaultness::Default(_) = defaultness {
498 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
502 ast::ItemKind::Trait(box ast::Trait { is_auto: ast::IsAuto::Yes, .. }) => {
507 "auto traits are experimental and possibly buggy"
511 ast::ItemKind::TraitAlias(..) => {
512 gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
515 ast::ItemKind::MacroDef(ast::MacroDef { macro_rules: false, .. }) => {
516 let msg = "`macro` is experimental";
517 gate_feature_post!(&self, decl_macro, i.span, msg);
520 ast::ItemKind::TyAlias(box ast::TyAlias { ty: Some(ref ty), .. }) => {
521 self.check_impl_trait(&ty)
527 visit::walk_item(self, i);
530 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
532 ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
533 let link_name = self.sess.first_attr_value_str_by_name(&i.attrs, sym::link_name);
535 link_name.map_or(false, |val| val.as_str().starts_with("llvm."));
539 link_llvm_intrinsics,
541 "linking to LLVM intrinsics is experimental"
545 ast::ForeignItemKind::TyAlias(..) => {
546 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
548 ast::ForeignItemKind::MacCall(..) => {}
551 visit::walk_foreign_item(self, i)
554 fn visit_ty(&mut self, ty: &'a ast::Ty) {
556 ast::TyKind::BareFn(ref bare_fn_ty) => {
557 // Function pointers cannot be `const`
558 self.check_extern(bare_fn_ty.ext, ast::Const::No);
560 ast::TyKind::Never => {
561 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
565 visit::walk_ty(self, ty)
568 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
569 if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
570 if let ast::TyKind::Never = output_ty.kind {
573 self.visit_ty(output_ty)
578 fn visit_expr(&mut self, e: &'a ast::Expr) {
580 ast::ExprKind::Box(_) => {
585 "box expression syntax is experimental; you can call `Box::new` instead"
588 ast::ExprKind::Type(..) => {
589 // To avoid noise about type ascription in common syntax errors, only emit if it
590 // is the *only* error.
591 if self.sess.parse_sess.span_diagnostic.err_count() == 0 {
596 "type ascription is experimental"
600 ast::ExprKind::TryBlock(_) => {
601 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
603 ast::ExprKind::Block(_, Some(label)) => {
608 "labels on blocks are unstable"
613 visit::walk_expr(self, e)
616 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
617 match &pattern.kind {
618 PatKind::Slice(pats) => {
620 let inner_pat = match &pat.kind {
621 PatKind::Ident(.., Some(pat)) => pat,
624 if let PatKind::Range(Some(_), None, Spanned { .. }) = inner_pat.kind {
627 half_open_range_patterns,
629 "`X..` patterns in slices are experimental"
634 PatKind::Box(..) => {
639 "box pattern syntax is experimental"
642 PatKind::Range(_, Some(_), Spanned { node: RangeEnd::Excluded, .. }) => {
645 exclusive_range_pattern,
647 "exclusive range pattern syntax is experimental"
652 visit::walk_pat(self, pattern)
655 fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
656 if let Some(header) = fn_kind.header() {
657 // Stability of const fn methods are covered in `visit_assoc_item` below.
658 self.check_extern(header.ext, header.constness);
661 if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
662 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
665 visit::walk_fn(self, fn_kind, span)
668 fn visit_assoc_constraint(&mut self, constraint: &'a AssocConstraint) {
669 if let AssocConstraintKind::Bound { .. } = constraint.kind {
672 associated_type_bounds,
674 "associated type bounds are unstable"
677 visit::walk_assoc_constraint(self, constraint)
680 fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
681 let is_fn = match i.kind {
682 ast::AssocItemKind::Fn(_) => true,
683 ast::AssocItemKind::TyAlias(box ast::TyAlias { ref generics, ref ty, .. }) => {
684 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
687 associated_type_defaults,
689 "associated type defaults are unstable"
692 if let Some(ty) = ty {
693 self.check_impl_trait(ty);
695 self.check_gat(generics, i.span);
700 if let ast::Defaultness::Default(_) = i.kind.defaultness() {
701 // Limit `min_specialization` to only specializing functions.
704 |x: &Features| x.specialization || (is_fn && x.min_specialization),
707 "specialization is unstable"
710 visit::walk_assoc_item(self, i, ctxt)
714 pub fn check_crate(krate: &ast::Crate, sess: &Session) {
715 maybe_stage_features(sess, krate);
716 check_incompatible_features(sess);
717 let mut visitor = PostExpansionVisitor { sess, features: &sess.features_untracked() };
719 let spans = sess.parse_sess.gated_spans.spans.borrow();
720 macro_rules! gate_all {
721 ($gate:ident, $msg:literal, $help:literal) => {
722 if let Some(spans) = spans.get(&sym::$gate) {
724 gate_feature_post!(&visitor, $gate, *span, $msg, $help);
728 ($gate:ident, $msg:literal) => {
729 if let Some(spans) = spans.get(&sym::$gate) {
731 gate_feature_post!(&visitor, $gate, *span, $msg);
738 "`if let` guards are experimental",
739 "you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`"
741 gate_all!(let_chains, "`let` expressions in this position are unstable");
744 "async closures are unstable",
745 "to use an async block, remove the `||`: `async {`"
747 gate_all!(more_qualified_paths, "usage of qualified paths in this context is experimental");
748 gate_all!(generators, "yield syntax is experimental");
749 gate_all!(raw_ref_op, "raw address of syntax is experimental");
750 gate_all!(const_trait_impl, "const trait impls are experimental");
751 gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
752 gate_all!(inline_const, "inline-const is experimental");
753 gate_all!(inline_const_pat, "inline-const in pattern position is experimental");
754 gate_all!(associated_const_equality, "associated const equality is incomplete");
755 gate_all!(yeet_expr, "`do yeet` expression is experimental");
757 // All uses of `gate_all!` below this point were added in #65742,
758 // and subsequently disabled (with the non-early gating readded).
759 macro_rules! gate_all {
760 ($gate:ident, $msg:literal) => {
761 // FIXME(eddyb) do something more useful than always
762 // disabling these uses of early feature-gatings.
764 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
765 gate_feature_post!(&visitor, $gate, *span, $msg);
771 gate_all!(trait_alias, "trait aliases are experimental");
772 gate_all!(associated_type_bounds, "associated type bounds are unstable");
773 gate_all!(decl_macro, "`macro` is experimental");
774 gate_all!(box_patterns, "box pattern syntax is experimental");
775 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
776 gate_all!(try_blocks, "`try` blocks are unstable");
777 gate_all!(label_break_value, "labels on blocks are unstable");
778 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
779 // To avoid noise about type ascription in common syntax errors,
780 // only emit if it is the *only* error. (Also check it last.)
781 if sess.parse_sess.span_diagnostic.err_count() == 0 {
782 gate_all!(type_ascription, "type ascription is experimental");
785 visit::walk_crate(&mut visitor, krate);
788 fn maybe_stage_features(sess: &Session, krate: &ast::Crate) {
789 // checks if `#![feature]` has been used to enable any lang feature
790 // does not check the same for lib features unless there's at least one
791 // declared lang feature
792 use rustc_errors::Applicability;
794 if !sess.opts.unstable_features.is_nightly_build() {
795 let lang_features = &sess.features_untracked().declared_lang_features;
796 if lang_features.len() == 0 {
799 for attr in krate.attrs.iter().filter(|attr| attr.has_name(sym::feature)) {
800 let mut err = struct_span_err!(
801 sess.parse_sess.span_diagnostic,
804 "`#![feature]` may not be used on the {} release channel",
805 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")
807 let mut all_stable = true;
809 attr.meta_item_list().into_iter().flatten().flat_map(|nested| nested.ident())
811 let name = ident.name;
812 let stable_since = lang_features
814 .flat_map(|&(feature, _, since)| if feature == name { since } else { None })
816 if let Some(since) = stable_since {
818 "the feature `{}` has been stable since {} and no longer requires \
819 an attribute to enable",
829 "remove the attribute",
831 Applicability::MachineApplicable,
839 fn check_incompatible_features(sess: &Session) {
840 let features = sess.features_untracked();
842 let declared_features = features
843 .declared_lang_features
846 .map(|(name, span, _)| (name, span))
847 .chain(features.declared_lib_features.iter().copied());
849 for (f1, f2) in rustc_feature::INCOMPATIBLE_FEATURES
851 .filter(|&&(f1, f2)| features.enabled(f1) && features.enabled(f2))
853 if let Some((f1_name, f1_span)) = declared_features.clone().find(|(name, _)| name == f1) {
854 if let Some((f2_name, f2_span)) = declared_features.clone().find(|(name, _)| name == f2)
856 let spans = vec![f1_span, f2_span];
857 sess.struct_span_err(
860 "features `{}` and `{}` are incompatible, using them at the same time \
865 .help("remove one of these features")