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::{AttributeGate, BuiltinAttribute, Features, GateIssue, BUILTIN_ATTRIBUTE_MAP};
7 use rustc_session::parse::{feature_err, feature_err_issue, feature_warn};
8 use rustc_session::Session;
9 use rustc_span::source_map::Spanned;
10 use rustc_span::symbol::sym;
12 use rustc_target::spec::abi;
14 macro_rules! gate_feature_fn {
15 ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr, $help: expr) => {{
16 let (visitor, has_feature, span, name, explain, help) =
17 (&*$visitor, $has_feature, $span, $name, $explain, $help);
18 let has_feature: bool = has_feature(visitor.features);
19 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
20 if !has_feature && !span.allows_unstable($name) {
21 feature_err(&visitor.sess.parse_sess, name, span, explain).help(help).emit();
24 ($visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
25 let (visitor, has_feature, span, name, explain) =
26 (&*$visitor, $has_feature, $span, $name, $explain);
27 let has_feature: bool = has_feature(visitor.features);
28 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
29 if !has_feature && !span.allows_unstable($name) {
30 feature_err(&visitor.sess.parse_sess, name, span, explain).emit();
33 (future_incompatible; $visitor: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
34 let (visitor, has_feature, span, name, explain) =
35 (&*$visitor, $has_feature, $span, $name, $explain);
36 let has_feature: bool = has_feature(visitor.features);
38 "gate_feature(feature = {:?}, span = {:?}); has? {} (future_incompatible)",
39 name, span, has_feature
41 if !has_feature && !span.allows_unstable($name) {
42 feature_warn(&visitor.sess.parse_sess, name, span, explain);
47 macro_rules! gate_feature_post {
48 ($visitor: expr, $feature: ident, $span: expr, $explain: expr, $help: expr) => {
49 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain, $help)
51 ($visitor: expr, $feature: ident, $span: expr, $explain: expr) => {
52 gate_feature_fn!($visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain)
54 (future_incompatible; $visitor: expr, $feature: ident, $span: expr, $explain: expr) => {
55 gate_feature_fn!(future_incompatible; $visitor, |x: &Features| x.$feature, $span, sym::$feature, $explain)
59 pub fn check_attribute(attr: &ast::Attribute, sess: &Session, features: &Features) {
60 PostExpansionVisitor { sess, features }.visit_attribute(attr)
63 struct PostExpansionVisitor<'a> {
66 // `sess` contains a `Features`, but this might not be that one.
67 features: &'a Features,
70 impl<'a> PostExpansionVisitor<'a> {
71 fn check_abi(&self, abi: ast::StrLit, constness: ast::Const) {
72 let ast::StrLit { symbol_unescaped, span, .. } = abi;
74 if let ast::Const::Yes(_) = constness {
75 match symbol_unescaped {
77 sym::Rust | sym::C => {}
78 abi => gate_feature_post!(
82 &format!("`{}` as a `const fn` ABI is unstable", abi)
87 match abi::is_enabled(&self.features, span, symbol_unescaped.as_str()) {
89 Err(abi::AbiDisabled::Unstable { feature, explain }) => {
91 &self.sess.parse_sess,
99 Err(abi::AbiDisabled::Unrecognized) => {
100 if self.sess.opts.pretty.map_or(true, |ppm| ppm.needs_hir()) {
101 self.sess.parse_sess.span_diagnostic.delay_span_bug(
104 "unrecognized ABI not caught in lowering: {}",
105 symbol_unescaped.as_str()
113 fn check_extern(&self, ext: ast::Extern, constness: ast::Const) {
114 if let ast::Extern::Explicit(abi, _) = ext {
115 self.check_abi(abi, constness);
119 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
120 let has_fields = variants.iter().any(|variant| match variant.data {
121 VariantData::Tuple(..) | VariantData::Struct(..) => true,
122 VariantData::Unit(..) => false,
125 let discriminant_spans = variants
127 .filter(|variant| match variant.data {
128 VariantData::Tuple(..) | VariantData::Struct(..) => false,
129 VariantData::Unit(..) => true,
131 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
132 .collect::<Vec<_>>();
134 if !discriminant_spans.is_empty() && has_fields {
135 let mut err = feature_err(
136 &self.sess.parse_sess,
137 sym::arbitrary_enum_discriminant,
138 discriminant_spans.clone(),
139 "custom discriminant values are not allowed in enums with tuple or struct variants",
141 for sp in discriminant_spans {
142 err.span_label(sp, "disallowed custom discriminant");
144 for variant in variants.iter() {
145 match &variant.data {
146 VariantData::Struct(..) => {
147 err.span_label(variant.span, "struct variant defined here");
149 VariantData::Tuple(..) => {
150 err.span_label(variant.span, "tuple variant defined here");
152 VariantData::Unit(..) => {}
159 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
160 fn check_impl_trait(&self, ty: &ast::Ty) {
161 struct ImplTraitVisitor<'a> {
162 vis: &'a PostExpansionVisitor<'a>,
164 impl Visitor<'_> for ImplTraitVisitor<'_> {
165 fn visit_ty(&mut self, ty: &ast::Ty) {
166 if let ast::TyKind::ImplTrait(..) = ty.kind {
169 type_alias_impl_trait,
171 "`impl Trait` in type aliases is unstable"
174 visit::walk_ty(self, ty);
177 ImplTraitVisitor { vis: self }.visit_ty(ty);
181 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
182 fn visit_attribute(&mut self, attr: &ast::Attribute) {
183 let attr_info = attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name));
184 // Check feature gates for built-in attributes.
185 if let Some(BuiltinAttribute {
186 gate: AttributeGate::Gated(_, name, descr, has_feature),
190 gate_feature_fn!(self, has_feature, attr.span, *name, descr);
192 // Check unstable flavors of the `#[doc]` attribute.
193 if attr.has_name(sym::doc) {
194 for nested_meta in attr.meta_item_list().unwrap_or_default() {
195 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
196 $(if nested_meta.has_name(sym::$name) {
197 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
198 gate_feature_post!(self, $feature, attr.span, msg);
204 cfg_hide => doc_cfg_hide
206 notable_trait => doc_notable_trait
209 if nested_meta.has_name(sym::keyword) {
210 let msg = "`#[doc(keyword)]` is meant for internal use only";
211 gate_feature_post!(self, rustdoc_internals, attr.span, msg);
214 if nested_meta.has_name(sym::fake_variadic) {
215 let msg = "`#[doc(fake_variadic)]` is meant for internal use only";
216 gate_feature_post!(self, rustdoc_internals, attr.span, msg);
221 // Emit errors for non-staged-api crates.
222 if !self.features.staged_api {
223 if attr.has_name(sym::unstable)
224 || attr.has_name(sym::stable)
225 || attr.has_name(sym::rustc_const_unstable)
226 || attr.has_name(sym::rustc_const_stable)
227 || attr.has_name(sym::rustc_default_body_unstable)
233 "stability attributes may not be used outside of the standard library",
240 fn visit_item(&mut self, i: &'a ast::Item) {
242 ast::ItemKind::ForeignMod(ref foreign_module) => {
243 if let Some(abi) = foreign_module.abi {
244 self.check_abi(abi, ast::Const::No);
248 ast::ItemKind::Fn(..) => {
249 if self.sess.contains_name(&i.attrs, sym::start) {
254 "`#[start]` functions are experimental \
255 and their signature may change \
261 ast::ItemKind::Struct(..) => {
262 for attr in self.sess.filter_by_name(&i.attrs, sym::repr) {
263 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
264 if item.has_name(sym::simd) {
269 "SIMD types are experimental and possibly buggy"
276 ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
277 for variant in variants {
278 match (&variant.data, &variant.disr_expr) {
279 (ast::VariantData::Unit(..), _) => {}
280 (_, Some(disr_expr)) => gate_feature_post!(
282 arbitrary_enum_discriminant,
283 disr_expr.value.span,
284 "discriminants on non-unit variants are experimental"
290 let has_feature = self.features.arbitrary_enum_discriminant;
291 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
292 self.maybe_report_invalid_custom_discriminants(&variants);
296 ast::ItemKind::Impl(box ast::Impl { polarity, defaultness, ref of_trait, .. }) => {
297 if let ast::ImplPolarity::Negative(span) = polarity {
301 span.to(of_trait.as_ref().map_or(span, |t| t.path.span)),
302 "negative trait bounds are not yet fully implemented; \
303 use marker types for now"
307 if let ast::Defaultness::Default(_) = defaultness {
308 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
312 ast::ItemKind::Trait(box ast::Trait { is_auto: ast::IsAuto::Yes, .. }) => {
317 "auto traits are experimental and possibly buggy"
321 ast::ItemKind::TraitAlias(..) => {
322 gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
325 ast::ItemKind::MacroDef(ast::MacroDef { macro_rules: false, .. }) => {
326 let msg = "`macro` is experimental";
327 gate_feature_post!(&self, decl_macro, i.span, msg);
330 ast::ItemKind::TyAlias(box ast::TyAlias { ty: Some(ref ty), .. }) => {
331 self.check_impl_trait(&ty)
337 visit::walk_item(self, i);
340 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
342 ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
343 let link_name = self.sess.first_attr_value_str_by_name(&i.attrs, sym::link_name);
345 link_name.map_or(false, |val| val.as_str().starts_with("llvm."));
349 link_llvm_intrinsics,
351 "linking to LLVM intrinsics is experimental"
355 ast::ForeignItemKind::TyAlias(..) => {
356 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
358 ast::ForeignItemKind::MacCall(..) => {}
361 visit::walk_foreign_item(self, i)
364 fn visit_ty(&mut self, ty: &'a ast::Ty) {
366 ast::TyKind::BareFn(ref bare_fn_ty) => {
367 // Function pointers cannot be `const`
368 self.check_extern(bare_fn_ty.ext, ast::Const::No);
370 ast::TyKind::Never => {
371 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
373 ast::TyKind::TraitObject(_, ast::TraitObjectSyntax::DynStar, ..) => {
374 gate_feature_post!(&self, dyn_star, ty.span, "dyn* trait objects are unstable");
378 visit::walk_ty(self, ty)
381 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
382 if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
383 if let ast::TyKind::Never = output_ty.kind {
386 self.visit_ty(output_ty)
391 fn visit_stmt(&mut self, stmt: &'a ast::Stmt) {
392 if let ast::StmtKind::Semi(expr) = &stmt.kind
393 && let ast::ExprKind::Assign(lhs, _, _) = &expr.kind
394 && let ast::ExprKind::Type(..) = lhs.kind
395 && self.sess.parse_sess.span_diagnostic.err_count() == 0
396 && !self.features.type_ascription
397 && !lhs.span.allows_unstable(sym::type_ascription)
399 // When we encounter a statement of the form `foo: Ty = val;`, this will emit a type
400 // ascription error, but the likely intention was to write a `let` statement. (#78907).
402 &self.sess.parse_sess,
403 sym::type_ascription,
405 "type ascription is experimental",
406 ).span_suggestion_verbose(
407 lhs.span.shrink_to_lo(),
408 "you might have meant to introduce a new binding",
410 Applicability::MachineApplicable,
413 visit::walk_stmt(self, stmt);
416 fn visit_expr(&mut self, e: &'a ast::Expr) {
418 ast::ExprKind::Box(_) => {
423 "box expression syntax is experimental; you can call `Box::new` instead"
426 ast::ExprKind::Type(..) => {
427 if self.sess.parse_sess.span_diagnostic.err_count() == 0 {
428 // To avoid noise about type ascription in common syntax errors,
429 // only emit if it is the *only* error.
434 "type ascription is experimental"
437 // And if it isn't, cancel the early-pass warning.
441 .steal_diagnostic(e.span, StashKey::EarlySyntaxWarning)
442 .map(|err| err.cancel());
445 ast::ExprKind::TryBlock(_) => {
446 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
450 visit::walk_expr(self, e)
453 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
454 match &pattern.kind {
455 PatKind::Slice(pats) => {
457 let inner_pat = match &pat.kind {
458 PatKind::Ident(.., Some(pat)) => pat,
461 if let PatKind::Range(Some(_), None, Spanned { .. }) = inner_pat.kind {
464 half_open_range_patterns_in_slices,
466 "`X..` patterns in slices are experimental"
471 PatKind::Box(..) => {
476 "box pattern syntax is experimental"
479 PatKind::Range(_, Some(_), Spanned { node: RangeEnd::Excluded, .. }) => {
482 exclusive_range_pattern,
484 "exclusive range pattern syntax is experimental"
489 visit::walk_pat(self, pattern)
492 fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
493 if let Some(header) = fn_kind.header() {
494 // Stability of const fn methods are covered in `visit_assoc_item` below.
495 self.check_extern(header.ext, header.constness);
498 if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
499 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
502 visit::walk_fn(self, fn_kind)
505 fn visit_assoc_constraint(&mut self, constraint: &'a AssocConstraint) {
506 if let AssocConstraintKind::Bound { .. } = constraint.kind {
509 associated_type_bounds,
511 "associated type bounds are unstable"
514 visit::walk_assoc_constraint(self, constraint)
517 fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
518 let is_fn = match i.kind {
519 ast::AssocItemKind::Fn(_) => true,
520 ast::AssocItemKind::Type(box ast::TyAlias { ref ty, .. }) => {
521 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
524 associated_type_defaults,
526 "associated type defaults are unstable"
529 if let Some(ty) = ty {
530 self.check_impl_trait(ty);
536 if let ast::Defaultness::Default(_) = i.kind.defaultness() {
537 // Limit `min_specialization` to only specializing functions.
540 |x: &Features| x.specialization || (is_fn && x.min_specialization),
543 "specialization is unstable"
546 visit::walk_assoc_item(self, i, ctxt)
550 pub fn check_crate(krate: &ast::Crate, sess: &Session) {
551 maybe_stage_features(sess, krate);
552 check_incompatible_features(sess);
553 let mut visitor = PostExpansionVisitor { sess, features: &sess.features_untracked() };
555 let spans = sess.parse_sess.gated_spans.spans.borrow();
556 macro_rules! gate_all {
557 ($gate:ident, $msg:literal, $help:literal) => {
558 if let Some(spans) = spans.get(&sym::$gate) {
560 gate_feature_post!(&visitor, $gate, *span, $msg, $help);
564 ($gate:ident, $msg:literal) => {
565 if let Some(spans) = spans.get(&sym::$gate) {
567 gate_feature_post!(&visitor, $gate, *span, $msg);
574 "`if let` guards are experimental",
575 "you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`"
577 gate_all!(let_chains, "`let` expressions in this position are unstable");
580 "async closures are unstable",
581 "to use an async block, remove the `||`: `async {`"
584 closure_lifetime_binder,
585 "`for<...>` binders for closures are experimental",
586 "consider removing `for<...>`"
588 gate_all!(more_qualified_paths, "usage of qualified paths in this context is experimental");
589 gate_all!(generators, "yield syntax is experimental");
590 gate_all!(raw_ref_op, "raw address of syntax is experimental");
591 gate_all!(const_trait_impl, "const trait impls are experimental");
593 half_open_range_patterns_in_slices,
594 "half-open range patterns in slices are unstable"
596 gate_all!(inline_const, "inline-const is experimental");
597 gate_all!(inline_const_pat, "inline-const in pattern position is experimental");
598 gate_all!(associated_const_equality, "associated const equality is incomplete");
599 gate_all!(yeet_expr, "`do yeet` expression is experimental");
601 // All uses of `gate_all!` below this point were added in #65742,
602 // and subsequently disabled (with the non-early gating readded).
603 // We emit an early future-incompatible warning for these.
604 // New syntax gates should go above here to get a hard error gate.
605 macro_rules! gate_all {
606 ($gate:ident, $msg:literal) => {
607 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
608 gate_feature_post!(future_incompatible; &visitor, $gate, *span, $msg);
613 gate_all!(trait_alias, "trait aliases are experimental");
614 gate_all!(associated_type_bounds, "associated type bounds are unstable");
615 gate_all!(decl_macro, "`macro` is experimental");
616 gate_all!(box_patterns, "box pattern syntax is experimental");
617 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
618 gate_all!(try_blocks, "`try` blocks are unstable");
619 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
620 gate_all!(type_ascription, "type ascription is experimental");
622 visit::walk_crate(&mut visitor, krate);
625 fn maybe_stage_features(sess: &Session, krate: &ast::Crate) {
626 // checks if `#![feature]` has been used to enable any lang feature
627 // does not check the same for lib features unless there's at least one
628 // declared lang feature
629 if !sess.opts.unstable_features.is_nightly_build() {
630 let lang_features = &sess.features_untracked().declared_lang_features;
631 if lang_features.len() == 0 {
634 for attr in krate.attrs.iter().filter(|attr| attr.has_name(sym::feature)) {
635 let mut err = struct_span_err!(
636 sess.parse_sess.span_diagnostic,
639 "`#![feature]` may not be used on the {} release channel",
640 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")
642 let mut all_stable = true;
644 attr.meta_item_list().into_iter().flatten().flat_map(|nested| nested.ident())
646 let name = ident.name;
647 let stable_since = lang_features
649 .flat_map(|&(feature, _, since)| if feature == name { since } else { None })
651 if let Some(since) = stable_since {
653 "the feature `{}` has been stable since {} and no longer requires \
654 an attribute to enable",
664 "remove the attribute",
666 Applicability::MachineApplicable,
674 fn check_incompatible_features(sess: &Session) {
675 let features = sess.features_untracked();
677 let declared_features = features
678 .declared_lang_features
681 .map(|(name, span, _)| (name, span))
682 .chain(features.declared_lib_features.iter().copied());
684 for (f1, f2) in rustc_feature::INCOMPATIBLE_FEATURES
686 .filter(|&&(f1, f2)| features.enabled(f1) && features.enabled(f2))
688 if let Some((f1_name, f1_span)) = declared_features.clone().find(|(name, _)| name == f1) {
689 if let Some((f2_name, f2_span)) = declared_features.clone().find(|(name, _)| name == f2)
691 let spans = vec![f1_span, f2_span];
692 sess.struct_span_err(
695 "features `{}` and `{}` are incompatible, using them at the same time \
700 .help("remove one of these features")