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, Applicability, StashKey};
6 use rustc_feature::Features;
7 use rustc_feature::{AttributeGate, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
8 use rustc_session::parse::{feature_err, feature_warn};
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(&visitor.sess.parse_sess, name, span, explain).help(help).emit();
26 ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
27 let (visitor, has_feature, span, name, explain) =
28 (&*$visitor, $has_feature, $span, $name, $explain);
29 let has_feature: bool = has_feature(visitor.features);
30 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
31 if !has_feature && !span.allows_unstable($name) {
32 feature_err(&visitor.sess.parse_sess, name, span, explain).emit();
35 (future_incompatible; $visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
36 let (visitor, has_feature, span, name, explain) =
37 (&*$visitor, $has_feature, $span, $name, $explain);
38 let has_feature: bool = has_feature(visitor.features);
40 "gate_feature(feature = {:?}, span = {:?}); has? {} (future_incompatible)",
41 name, span, has_feature
43 if !has_feature && !span.allows_unstable($name) {
44 feature_warn(&visitor.sess.parse_sess, name, span, explain);
49 macro_rules! gate_feature_post {
50 ($visitor: expr, $feature: ident, $span: expr, $explain: expr, $help: expr) => {
51 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain, $help)
53 ($visitor: expr, $feature: ident, $span: expr, $explain: expr) => {
54 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain)
56 (future_incompatible; $visitor: expr, $feature: ident, $span: expr, $explain: expr) => {
57 gate_feature_fn!(future_incompatible; $visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain)
61 pub fn check_attribute(attr: &ast::Attribute, sess: &Session, features: &Features) {
62 PostExpansionVisitor { sess, features }.visit_attribute(attr)
65 struct PostExpansionVisitor<'a> {
68 // `sess` contains a `Features`, but this might not be that one.
69 features: &'a Features,
72 impl<'a> PostExpansionVisitor<'a> {
73 fn check_abi(&self, abi: ast::StrLit, constness: ast::Const) {
74 let ast::StrLit { symbol_unescaped, span, .. } = abi;
76 if let ast::Const::Yes(_) = constness {
77 match symbol_unescaped {
79 sym::Rust | sym::C => {}
80 abi => gate_feature_post!(
84 &format!("`{}` as a `const fn` ABI is unstable", abi)
89 match symbol_unescaped.as_str() {
91 "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
94 gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
96 "platform-intrinsic" => {
101 "platform intrinsics are experimental and possibly buggy"
109 "vectorcall is experimental and subject to change"
117 "thiscall is experimental and subject to change"
125 "rust-call ABI is subject to change"
133 "rust-cold is experimental and subject to change"
141 "PTX ABIs are experimental and subject to change"
149 "unadjusted ABI is an implementation detail and perma-unstable"
152 "msp430-interrupt" => {
155 abi_msp430_interrupt,
157 "msp430-interrupt ABI is experimental and subject to change"
165 "x86-interrupt ABI is experimental and subject to change"
173 "amdgpu-kernel ABI is experimental and subject to change"
176 "avr-interrupt" | "avr-non-blocking-interrupt" => {
181 "avr-interrupt and avr-non-blocking-interrupt ABIs are experimental and subject to change"
189 "efiapi ABI is experimental and subject to change"
192 "C-cmse-nonsecure-call" => {
195 abi_c_cmse_nonsecure_call,
197 "C-cmse-nonsecure-call ABI is experimental and subject to change"
205 "C-unwind ABI is experimental and subject to change"
208 "stdcall-unwind" => {
213 "stdcall-unwind ABI is experimental and subject to change"
221 "system-unwind ABI is experimental and subject to change"
224 "thiscall-unwind" => {
229 "thiscall-unwind ABI is experimental and subject to change"
237 "cdecl-unwind ABI is experimental and subject to change"
240 "fastcall-unwind" => {
245 "fastcall-unwind ABI is experimental and subject to change"
248 "vectorcall-unwind" => {
253 "vectorcall-unwind ABI is experimental and subject to change"
261 "aapcs-unwind ABI is experimental and subject to change"
269 "win64-unwind ABI is experimental and subject to change"
277 "sysv64-unwind ABI is experimental and subject to change"
285 "wasm ABI is experimental and subject to change"
289 if self.sess.opts.pretty.map_or(true, |ppm| ppm.needs_hir()) {
290 self.sess.parse_sess.span_diagnostic.delay_span_bug(
292 &format!("unrecognized ABI not caught in lowering: {}", abi),
299 fn check_extern(&self, ext: ast::Extern, constness: ast::Const) {
300 if let ast::Extern::Explicit(abi, _) = ext {
301 self.check_abi(abi, constness);
305 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
306 let has_fields = variants.iter().any(|variant| match variant.data {
307 VariantData::Tuple(..) | VariantData::Struct(..) => true,
308 VariantData::Unit(..) => false,
311 let discriminant_spans = variants
313 .filter(|variant| match variant.data {
314 VariantData::Tuple(..) | VariantData::Struct(..) => false,
315 VariantData::Unit(..) => true,
317 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
318 .collect::<Vec<_>>();
320 if !discriminant_spans.is_empty() && has_fields {
321 let mut err = feature_err(
322 &self.sess.parse_sess,
323 sym::arbitrary_enum_discriminant,
324 discriminant_spans.clone(),
325 "custom discriminant values are not allowed in enums with tuple or struct variants",
327 for sp in discriminant_spans {
328 err.span_label(sp, "disallowed custom discriminant");
330 for variant in variants.iter() {
331 match &variant.data {
332 VariantData::Struct(..) => {
333 err.span_label(variant.span, "struct variant defined here");
335 VariantData::Tuple(..) => {
336 err.span_label(variant.span, "tuple variant defined here");
338 VariantData::Unit(..) => {}
345 fn check_gat(&self, generics: &ast::Generics, span: Span) {
346 if !generics.params.is_empty() {
349 generic_associated_types,
351 "generic associated types are unstable"
354 if !generics.where_clause.predicates.is_empty() {
357 generic_associated_types,
359 "where clauses on associated types are unstable"
364 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
365 fn check_impl_trait(&self, ty: &ast::Ty) {
366 struct ImplTraitVisitor<'a> {
367 vis: &'a PostExpansionVisitor<'a>,
369 impl Visitor<'_> for ImplTraitVisitor<'_> {
370 fn visit_ty(&mut self, ty: &ast::Ty) {
371 if let ast::TyKind::ImplTrait(..) = ty.kind {
374 type_alias_impl_trait,
376 "`impl Trait` in type aliases is unstable"
379 visit::walk_ty(self, ty);
382 ImplTraitVisitor { vis: self }.visit_ty(ty);
386 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
387 fn visit_attribute(&mut self, attr: &ast::Attribute) {
388 let attr_info = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
389 // Check feature gates for built-in attributes.
390 if let Some(BuiltinAttribute {
391 gate: AttributeGate::Gated(_, name, descr, has_feature),
395 gate_feature_fn!(self, has_feature, attr.span, *name, descr);
397 // Check unstable flavors of the `#[doc]` attribute.
398 if attr.has_name(sym::doc) {
399 for nested_meta in attr.meta_item_list().unwrap_or_default() {
400 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
401 $(if nested_meta.has_name(sym::$name) {
402 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
403 gate_feature_post!(self, $feature, attr.span, msg);
409 cfg_hide => doc_cfg_hide
411 notable_trait => doc_notable_trait
414 if nested_meta.has_name(sym::keyword) {
415 let msg = "`#[doc(keyword)]` is meant for internal use only";
416 gate_feature_post!(self, rustdoc_internals, attr.span, msg);
419 if nested_meta.has_name(sym::fake_variadic) {
420 let msg = "`#[doc(fake_variadic)]` is meant for internal use only";
421 gate_feature_post!(self, rustdoc_internals, attr.span, msg);
426 // Emit errors for non-staged-api crates.
427 if !self.features.staged_api {
428 if attr.has_name(sym::unstable)
429 || attr.has_name(sym::stable)
430 || attr.has_name(sym::rustc_const_unstable)
431 || attr.has_name(sym::rustc_const_stable)
432 || attr.has_name(sym::rustc_default_body_unstable)
438 "stability attributes may not be used outside of the standard library",
445 fn visit_item(&mut self, i: &'a ast::Item) {
447 ast::ItemKind::ForeignMod(ref foreign_module) => {
448 if let Some(abi) = foreign_module.abi {
449 self.check_abi(abi, ast::Const::No);
453 ast::ItemKind::Fn(..) => {
454 if self.sess.contains_name(&i.attrs, sym::start) {
459 "`#[start]` functions are experimental \
460 and their signature may change \
466 ast::ItemKind::Struct(..) => {
467 for attr in self.sess.filter_by_name(&i.attrs, sym::repr) {
468 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
469 if item.has_name(sym::simd) {
474 "SIMD types are experimental and possibly buggy"
481 ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
482 for variant in variants {
483 match (&variant.data, &variant.disr_expr) {
484 (ast::VariantData::Unit(..), _) => {}
485 (_, Some(disr_expr)) => gate_feature_post!(
487 arbitrary_enum_discriminant,
488 disr_expr.value.span,
489 "discriminants on non-unit variants are experimental"
495 let has_feature = self.features.arbitrary_enum_discriminant;
496 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
497 self.maybe_report_invalid_custom_discriminants(&variants);
501 ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, ref of_trait, .. }) => {
502 if let ast::ImplPolarity::Negative(span) = polarity {
506 span.to(of_trait.as_ref().map_or(span, |t| t.path.span)),
507 "negative trait bounds are not yet fully implemented; \
508 use marker types for now"
512 if let ast::Defaultness::Default(_) = defaultness {
513 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
517 ast::ItemKind::Trait(box ast::Trait { is_auto: ast::IsAuto::Yes, .. }) => {
522 "auto traits are experimental and possibly buggy"
526 ast::ItemKind::TraitAlias(..) => {
527 gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
530 ast::ItemKind::MacroDef(ast::MacroDef { macro_rules: false, .. }) => {
531 let msg = "`macro` is experimental";
532 gate_feature_post!(&self, decl_macro, i.span, msg);
535 ast::ItemKind::TyAlias(box ast::TyAlias { ty: Some(ref ty), .. }) => {
536 self.check_impl_trait(&ty)
542 visit::walk_item(self, i);
545 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
547 ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
548 let link_name = self.sess.first_attr_value_str_by_name(&i.attrs, sym::link_name);
550 link_name.map_or(false, |val| val.as_str().starts_with("llvm."));
554 link_llvm_intrinsics,
556 "linking to LLVM intrinsics is experimental"
560 ast::ForeignItemKind::TyAlias(..) => {
561 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
563 ast::ForeignItemKind::MacCall(..) => {}
566 visit::walk_foreign_item(self, i)
569 fn visit_ty(&mut self, ty: &'a ast::Ty) {
571 ast::TyKind::BareFn(ref bare_fn_ty) => {
572 // Function pointers cannot be `const`
573 self.check_extern(bare_fn_ty.ext, ast::Const::No);
575 ast::TyKind::Never => {
576 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
580 visit::walk_ty(self, ty)
583 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
584 if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
585 if let ast::TyKind::Never = output_ty.kind {
588 self.visit_ty(output_ty)
593 fn visit_stmt(&mut self, stmt: &'a ast::Stmt) {
594 if let ast::StmtKind::Semi(expr) = &stmt.kind
595 && let ast::ExprKind::Assign(lhs, _, _) = &expr.kind
596 && let ast::ExprKind::Type(..) = lhs.kind
597 && self.sess.parse_sess.span_diagnostic.err_count() == 0
598 && !self.features.type_ascription
599 && !lhs.span.allows_unstable(sym::type_ascription)
601 // When we encounter a statement of the form `foo: Ty = val;`, this will emit a type
602 // ascription error, but the likely intention was to write a `let` statement. (#78907).
604 &self.sess.parse_sess,
605 sym::type_ascription,
607 "type ascription is experimental",
608 ).span_suggestion_verbose(
609 lhs.span.shrink_to_lo(),
610 "you might have meant to introduce a new binding",
612 Applicability::MachineApplicable,
615 visit::walk_stmt(self, stmt);
618 fn visit_expr(&mut self, e: &'a ast::Expr) {
620 ast::ExprKind::Box(_) => {
625 "box expression syntax is experimental; you can call `Box::new` instead"
628 ast::ExprKind::Type(..) => {
629 if self.sess.parse_sess.span_diagnostic.err_count() == 0 {
630 // To avoid noise about type ascription in common syntax errors,
631 // only emit if it is the *only* error.
636 "type ascription is experimental"
639 // And if it isn't, cancel the early-pass warning.
643 .steal_diagnostic(e.span, StashKey::EarlySyntaxWarning)
644 .map(|err| err.cancel());
647 ast::ExprKind::TryBlock(_) => {
648 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
652 visit::walk_expr(self, e)
655 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
656 match &pattern.kind {
657 PatKind::Slice(pats) => {
659 let inner_pat = match &pat.kind {
660 PatKind::Ident(.., Some(pat)) => pat,
663 if let PatKind::Range(Some(_), None, Spanned { .. }) = inner_pat.kind {
666 half_open_range_patterns,
668 "`X..` patterns in slices are experimental"
673 PatKind::Box(..) => {
678 "box pattern syntax is experimental"
681 PatKind::Range(_, Some(_), Spanned { node: RangeEnd::Excluded, .. }) => {
684 exclusive_range_pattern,
686 "exclusive range pattern syntax is experimental"
691 visit::walk_pat(self, pattern)
694 fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
695 if let Some(header) = fn_kind.header() {
696 // Stability of const fn methods are covered in `visit_assoc_item` below.
697 self.check_extern(header.ext, header.constness);
700 if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
701 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
704 visit::walk_fn(self, fn_kind, span)
707 fn visit_assoc_constraint(&mut self, constraint: &'a AssocConstraint) {
708 if let AssocConstraintKind::Bound { .. } = constraint.kind {
711 associated_type_bounds,
713 "associated type bounds are unstable"
716 visit::walk_assoc_constraint(self, constraint)
719 fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
720 let is_fn = match i.kind {
721 ast::AssocItemKind::Fn(_) => true,
722 ast::AssocItemKind::TyAlias(box ast::TyAlias { ref generics, ref ty, .. }) => {
723 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
726 associated_type_defaults,
728 "associated type defaults are unstable"
731 if let Some(ty) = ty {
732 self.check_impl_trait(ty);
734 self.check_gat(generics, i.span);
739 if let ast::Defaultness::Default(_) = i.kind.defaultness() {
740 // Limit `min_specialization` to only specializing functions.
743 |x: &Features| x.specialization || (is_fn && x.min_specialization),
746 "specialization is unstable"
749 visit::walk_assoc_item(self, i, ctxt)
753 pub fn check_crate(krate: &ast::Crate, sess: &Session) {
754 maybe_stage_features(sess, krate);
755 check_incompatible_features(sess);
756 let mut visitor = PostExpansionVisitor { sess, features: &sess.features_untracked() };
758 let spans = sess.parse_sess.gated_spans.spans.borrow();
759 macro_rules! gate_all {
760 ($gate:ident, $msg:literal, $help:literal) => {
761 if let Some(spans) = spans.get(&sym::$gate) {
763 gate_feature_post!(&visitor, $gate, *span, $msg, $help);
767 ($gate:ident, $msg:literal) => {
768 if let Some(spans) = spans.get(&sym::$gate) {
770 gate_feature_post!(&visitor, $gate, *span, $msg);
777 "`if let` guards are experimental",
778 "you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`"
782 "async closures are unstable",
783 "to use an async block, remove the `||`: `async {`"
786 closure_lifetime_binder,
787 "`for<...>` binders for closures are experimental",
788 "consider removing `for<...>`"
790 gate_all!(more_qualified_paths, "usage of qualified paths in this context is experimental");
791 gate_all!(generators, "yield syntax is experimental");
792 gate_all!(raw_ref_op, "raw address of syntax is experimental");
793 gate_all!(const_trait_impl, "const trait impls are experimental");
794 gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
795 gate_all!(inline_const, "inline-const is experimental");
796 gate_all!(inline_const_pat, "inline-const in pattern position is experimental");
797 gate_all!(associated_const_equality, "associated const equality is incomplete");
798 gate_all!(yeet_expr, "`do yeet` expression is experimental");
800 // All uses of `gate_all!` below this point were added in #65742,
801 // and subsequently disabled (with the non-early gating readded).
802 // We emit an early future-incompatible warning for these.
803 // New syntax gates should go above here to get a hard error gate.
804 macro_rules! gate_all {
805 ($gate:ident, $msg:literal) => {
806 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
807 gate_feature_post!(future_incompatible; &visitor, $gate, *span, $msg);
812 gate_all!(trait_alias, "trait aliases are experimental");
813 gate_all!(associated_type_bounds, "associated type bounds are unstable");
814 gate_all!(decl_macro, "`macro` is experimental");
815 gate_all!(box_patterns, "box pattern syntax is experimental");
816 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
817 gate_all!(try_blocks, "`try` blocks are unstable");
818 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
819 gate_all!(type_ascription, "type ascription is experimental");
821 visit::walk_crate(&mut visitor, krate);
824 fn maybe_stage_features(sess: &Session, krate: &ast::Crate) {
825 // checks if `#![feature]` has been used to enable any lang feature
826 // does not check the same for lib features unless there's at least one
827 // declared lang feature
828 if !sess.opts.unstable_features.is_nightly_build() {
829 let lang_features = &sess.features_untracked().declared_lang_features;
830 if lang_features.len() == 0 {
833 for attr in krate.attrs.iter().filter(|attr| attr.has_name(sym::feature)) {
834 let mut err = struct_span_err!(
835 sess.parse_sess.span_diagnostic,
838 "`#![feature]` may not be used on the {} release channel",
839 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")
841 let mut all_stable = true;
843 attr.meta_item_list().into_iter().flatten().flat_map(|nested| nested.ident())
845 let name = ident.name;
846 let stable_since = lang_features
848 .flat_map(|&(feature, _, since)| if feature == name { since } else { None })
850 if let Some(since) = stable_since {
852 "the feature `{}` has been stable since {} and no longer requires \
853 an attribute to enable",
863 "remove the attribute",
865 Applicability::MachineApplicable,
873 fn check_incompatible_features(sess: &Session) {
874 let features = sess.features_untracked();
876 let declared_features = features
877 .declared_lang_features
880 .map(|(name, span, _)| (name, span))
881 .chain(features.declared_lib_features.iter().copied());
883 for (f1, f2) in rustc_feature::INCOMPATIBLE_FEATURES
885 .filter(|&&(f1, f2)| features.enabled(f1) && features.enabled(f2))
887 if let Some((f1_name, f1_span)) = declared_features.clone().find(|(name, _)| name == f1) {
888 if let Some((f2_name, f2_span)) = declared_features.clone().find(|(name, _)| name == f2)
890 let spans = vec![f1_span, f2_span];
891 sess.struct_span_err(
894 "features `{}` and `{}` are incompatible, using them at the same time \
899 .help("remove one of these features")