1 use rustc_ast::ast::{self, AssocTyConstraint, AssocTyConstraintKind, NodeId};
2 use rustc_ast::ast::{GenericParam, GenericParamKind, PatKind, RangeEnd, VariantData};
4 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
5 use rustc_errors::{struct_span_err, Handler};
6 use rustc_feature::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
7 use rustc_feature::{Features, GateIssue, UnstableFeatures};
8 use rustc_session::parse::{feature_err, feature_err_issue, ParseSess};
9 use rustc_span::source_map::Spanned;
10 use rustc_span::symbol::sym;
15 macro_rules! gate_feature_fn {
16 ($cx: expr, $has_feature: expr, $span: expr, $name: expr, $explain: expr) => {{
17 let (cx, has_feature, span, name, explain) = (&*$cx, $has_feature, $span, $name, $explain);
18 let has_feature: bool = has_feature(&$cx.features);
19 debug!("gate_feature(feature = {:?}, span = {:?}); has? {}", name, span, has_feature);
20 if !has_feature && !span.allows_unstable($name) {
21 feature_err_issue(cx.parse_sess, name, span, GateIssue::Language, explain).emit();
26 macro_rules! gate_feature_post {
27 ($cx: expr, $feature: ident, $span: expr, $explain: expr) => {
28 gate_feature_fn!($cx, |x: &Features| x.$feature, $span, sym::$feature, $explain)
32 pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
33 PostExpansionVisitor { parse_sess, features }.visit_attribute(attr)
36 struct PostExpansionVisitor<'a> {
37 parse_sess: &'a ParseSess,
38 features: &'a Features,
41 impl<'a> PostExpansionVisitor<'a> {
42 fn check_abi(&self, abi: ast::StrLit) {
43 let ast::StrLit { symbol_unescaped, span, .. } = abi;
45 match &*symbol_unescaped.as_str() {
47 "Rust" | "C" | "cdecl" | "stdcall" | "fastcall" | "aapcs" | "win64" | "sysv64"
50 gate_feature_post!(&self, intrinsics, span, "intrinsics are subject to change");
52 "platform-intrinsic" => {
57 "platform intrinsics are experimental and possibly buggy"
65 "vectorcall is experimental and subject to change"
73 "thiscall is experimental and subject to change"
81 "rust-call ABI is subject to change"
89 "PTX ABIs are experimental and subject to change"
97 "unadjusted ABI is an implementation detail and perma-unstable"
100 "msp430-interrupt" => {
103 abi_msp430_interrupt,
105 "msp430-interrupt ABI is experimental and subject to change"
113 "x86-interrupt ABI is experimental and subject to change"
121 "amdgpu-kernel ABI is experimental and subject to change"
129 "efiapi ABI is experimental and subject to change"
135 .delay_span_bug(span, &format!("unrecognized ABI not caught in lowering: {}", abi)),
139 fn check_extern(&self, ext: ast::Extern) {
140 if let ast::Extern::Explicit(abi) = ext {
145 fn maybe_report_invalid_custom_discriminants(&self, variants: &[ast::Variant]) {
146 let has_fields = variants.iter().any(|variant| match variant.data {
147 VariantData::Tuple(..) | VariantData::Struct(..) => true,
148 VariantData::Unit(..) => false,
151 let discriminant_spans = variants
153 .filter(|variant| match variant.data {
154 VariantData::Tuple(..) | VariantData::Struct(..) => false,
155 VariantData::Unit(..) => true,
157 .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
158 .collect::<Vec<_>>();
160 if !discriminant_spans.is_empty() && has_fields {
161 let mut err = feature_err(
163 sym::arbitrary_enum_discriminant,
164 discriminant_spans.clone(),
165 "custom discriminant values are not allowed in enums with tuple or struct variants",
167 for sp in discriminant_spans {
168 err.span_label(sp, "disallowed custom discriminant");
170 for variant in variants.iter() {
171 match &variant.data {
172 VariantData::Struct(..) => {
173 err.span_label(variant.span, "struct variant defined here");
175 VariantData::Tuple(..) => {
176 err.span_label(variant.span, "tuple variant defined here");
178 VariantData::Unit(..) => {}
185 fn check_gat(&self, generics: &ast::Generics, span: Span) {
186 if !generics.params.is_empty() {
189 generic_associated_types,
191 "generic associated types are unstable"
194 if !generics.where_clause.predicates.is_empty() {
197 generic_associated_types,
199 "where clauses on associated types are unstable"
204 /// Feature gate `impl Trait` inside `type Alias = $type_expr;`.
205 fn check_impl_trait(&self, ty: &ast::Ty) {
206 struct ImplTraitVisitor<'a> {
207 vis: &'a PostExpansionVisitor<'a>,
209 impl Visitor<'_> for ImplTraitVisitor<'_> {
210 fn visit_ty(&mut self, ty: &ast::Ty) {
211 if let ast::TyKind::ImplTrait(..) = ty.kind {
214 type_alias_impl_trait,
216 "`impl Trait` in type aliases is unstable"
219 visit::walk_ty(self, ty);
222 ImplTraitVisitor { vis: self }.visit_ty(ty);
226 impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
227 fn visit_attribute(&mut self, attr: &ast::Attribute) {
229 attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
230 // Check feature gates for built-in attributes.
231 if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
232 gate_feature_fn!(self, has_feature, attr.span, name, descr);
234 // Check unstable flavors of the `#[doc]` attribute.
235 if attr.check_name(sym::doc) {
236 for nested_meta in attr.meta_item_list().unwrap_or_default() {
237 macro_rules! gate_doc { ($($name:ident => $feature:ident)*) => {
238 $(if nested_meta.check_name(sym::$name) {
239 let msg = concat!("`#[doc(", stringify!($name), ")]` is experimental");
240 gate_feature_post!(self, $feature, attr.span, msg);
245 include => external_doc
249 keyword => doc_keyword
255 fn visit_name(&mut self, sp: Span, name: ast::Name) {
256 if !name.as_str().is_ascii() {
260 self.parse_sess.source_map().def_span(sp),
261 "non-ascii idents are not fully supported"
266 fn visit_item(&mut self, i: &'a ast::Item) {
268 ast::ItemKind::ForeignMod(ref foreign_module) => {
269 if let Some(abi) = foreign_module.abi {
274 ast::ItemKind::Fn(..) => {
275 if attr::contains_name(&i.attrs[..], sym::plugin_registrar) {
280 "compiler plugins are experimental and possibly buggy"
283 if attr::contains_name(&i.attrs[..], sym::start) {
288 "`#[start]` functions are experimental \
289 and their signature may change \
293 if attr::contains_name(&i.attrs[..], sym::main) {
298 "declaration of a non-standard `#[main]` \
299 function may change over time, for now \
300 a top-level `fn main()` is required"
305 ast::ItemKind::Struct(..) => {
306 for attr in attr::filter_by_name(&i.attrs[..], sym::repr) {
307 for item in attr.meta_item_list().unwrap_or_else(Vec::new) {
308 if item.check_name(sym::simd) {
313 "SIMD types are experimental and possibly buggy"
320 ast::ItemKind::Enum(ast::EnumDef { ref variants, .. }, ..) => {
321 for variant in variants {
322 match (&variant.data, &variant.disr_expr) {
323 (ast::VariantData::Unit(..), _) => {}
324 (_, Some(disr_expr)) => gate_feature_post!(
326 arbitrary_enum_discriminant,
327 disr_expr.value.span,
328 "discriminants on non-unit variants are experimental"
334 let has_feature = self.features.arbitrary_enum_discriminant;
335 if !has_feature && !i.span.allows_unstable(sym::arbitrary_enum_discriminant) {
336 self.maybe_report_invalid_custom_discriminants(&variants);
340 ast::ItemKind::Impl { polarity, defaultness, .. } => {
341 if polarity == ast::ImplPolarity::Negative {
344 optin_builtin_traits,
346 "negative trait bounds are not yet fully implemented; \
347 use marker types for now"
351 if let ast::Defaultness::Default(_) = defaultness {
352 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
356 ast::ItemKind::Trait(ast::IsAuto::Yes, ..) => {
359 optin_builtin_traits,
361 "auto traits are experimental and possibly buggy"
365 ast::ItemKind::TraitAlias(..) => {
366 gate_feature_post!(&self, trait_alias, i.span, "trait aliases are experimental");
369 ast::ItemKind::MacroDef(ast::MacroDef { legacy: false, .. }) => {
370 let msg = "`macro` is experimental";
371 gate_feature_post!(&self, decl_macro, i.span, msg);
374 ast::ItemKind::TyAlias(_, _, _, Some(ref ty)) => self.check_impl_trait(&ty),
379 visit::walk_item(self, i);
382 fn visit_foreign_item(&mut self, i: &'a ast::ForeignItem) {
384 ast::ForeignItemKind::Fn(..) | ast::ForeignItemKind::Static(..) => {
385 let link_name = attr::first_attr_value_str_by_name(&i.attrs, sym::link_name);
386 let links_to_llvm = match link_name {
387 Some(val) => val.as_str().starts_with("llvm."),
393 link_llvm_intrinsics,
395 "linking to LLVM intrinsics is experimental"
399 ast::ForeignItemKind::TyAlias(..) => {
400 gate_feature_post!(&self, extern_types, i.span, "extern types are experimental");
402 ast::ForeignItemKind::Macro(..) => {}
405 visit::walk_foreign_item(self, i)
408 fn visit_ty(&mut self, ty: &'a ast::Ty) {
410 ast::TyKind::BareFn(ref bare_fn_ty) => {
411 self.check_extern(bare_fn_ty.ext);
413 ast::TyKind::Never => {
414 gate_feature_post!(&self, never_type, ty.span, "the `!` type is experimental");
418 visit::walk_ty(self, ty)
421 fn visit_fn_ret_ty(&mut self, ret_ty: &'a ast::FnRetTy) {
422 if let ast::FnRetTy::Ty(ref output_ty) = *ret_ty {
423 if let ast::TyKind::Never = output_ty.kind {
426 self.visit_ty(output_ty)
431 fn visit_expr(&mut self, e: &'a ast::Expr) {
433 ast::ExprKind::Box(_) => {
438 "box expression syntax is experimental; you can call `Box::new` instead"
441 ast::ExprKind::Type(..) => {
442 // To avoid noise about type ascription in common syntax errors, only emit if it
443 // is the *only* error.
444 if self.parse_sess.span_diagnostic.err_count() == 0 {
449 "type ascription is experimental"
453 ast::ExprKind::TryBlock(_) => {
454 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
456 ast::ExprKind::Block(_, opt_label) => {
457 if let Some(label) = opt_label {
462 "labels on blocks are unstable"
468 visit::walk_expr(self, e)
471 fn visit_pat(&mut self, pattern: &'a ast::Pat) {
472 match &pattern.kind {
473 PatKind::Box(..) => {
478 "box pattern syntax is experimental"
481 PatKind::Range(_, _, Spanned { node: RangeEnd::Excluded, .. }) => {
484 exclusive_range_pattern,
486 "exclusive range pattern syntax is experimental"
491 visit::walk_pat(self, pattern)
494 fn visit_fn(&mut self, fn_kind: FnKind<'a>, span: Span, _: NodeId) {
495 if let Some(header) = fn_kind.header() {
496 // Stability of const fn methods are covered in `visit_assoc_item` below.
497 self.check_extern(header.ext);
499 if let (ast::Const::Yes(_), ast::Extern::Implicit)
500 | (ast::Const::Yes(_), ast::Extern::Explicit(_)) = (header.constness, header.ext)
506 "`const extern fn` definitions are unstable"
511 if fn_kind.ctxt() != Some(FnCtxt::Foreign) && fn_kind.decl().c_variadic() {
512 gate_feature_post!(&self, c_variadic, span, "C-variadic functions are unstable");
515 visit::walk_fn(self, fn_kind, span)
518 fn visit_generic_param(&mut self, param: &'a GenericParam) {
520 GenericParamKind::Const { .. } => gate_feature_post!(
524 "const generics are unstable"
528 visit::walk_generic_param(self, param)
531 fn visit_assoc_ty_constraint(&mut self, constraint: &'a AssocTyConstraint) {
532 match constraint.kind {
533 AssocTyConstraintKind::Bound { .. } => gate_feature_post!(
535 associated_type_bounds,
537 "associated type bounds are unstable"
541 visit::walk_assoc_ty_constraint(self, constraint)
544 fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
545 if let ast::Defaultness::Default(_) = i.kind.defaultness() {
546 gate_feature_post!(&self, specialization, i.span, "specialization is unstable");
550 ast::AssocItemKind::Fn(_, ref sig, _, _) => {
551 if let (ast::Const::Yes(_), AssocCtxt::Trait) = (sig.header.constness, ctxt) {
552 gate_feature_post!(&self, const_fn, i.span, "const fn is unstable");
555 ast::AssocItemKind::TyAlias(_, ref generics, _, ref ty) => {
556 if let (Some(_), AssocCtxt::Trait) = (ty, ctxt) {
559 associated_type_defaults,
561 "associated type defaults are unstable"
564 if let Some(ty) = ty {
565 self.check_impl_trait(ty);
567 self.check_gat(generics, i.span);
571 visit::walk_assoc_item(self, i, ctxt)
574 fn visit_vis(&mut self, vis: &'a ast::Visibility) {
575 if let ast::VisibilityKind::Crate(ast::CrateSugar::JustCrate) = vis.node {
578 crate_visibility_modifier,
580 "`crate` visibility modifier is experimental"
583 visit::walk_vis(self, vis)
589 parse_sess: &ParseSess,
591 unstable: UnstableFeatures,
593 maybe_stage_features(&parse_sess.span_diagnostic, krate, unstable);
594 let mut visitor = PostExpansionVisitor { parse_sess, features };
596 let spans = parse_sess.gated_spans.spans.borrow();
597 macro_rules! gate_all {
598 ($gate:ident, $msg:literal) => {
599 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
600 gate_feature_post!(&visitor, $gate, *span, $msg);
604 gate_all!(let_chains, "`let` expressions in this position are experimental");
605 gate_all!(async_closure, "async closures are unstable");
606 gate_all!(generators, "yield syntax is experimental");
607 gate_all!(or_patterns, "or-patterns syntax is experimental");
608 gate_all!(raw_ref_op, "raw address of syntax is experimental");
609 gate_all!(const_trait_bound_opt_out, "`?const` on trait bounds is experimental");
610 gate_all!(const_trait_impl, "const trait impls are experimental");
611 gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
613 // All uses of `gate_all!` below this point were added in #65742,
614 // and subsequently disabled (with the non-early gating readded).
615 macro_rules! gate_all {
616 ($gate:ident, $msg:literal) => {
617 // FIXME(eddyb) do something more useful than always
618 // disabling these uses of early feature-gatings.
620 for span in spans.get(&sym::$gate).unwrap_or(&vec![]) {
621 gate_feature_post!(&visitor, $gate, *span, $msg);
627 gate_all!(trait_alias, "trait aliases are experimental");
628 gate_all!(associated_type_bounds, "associated type bounds are unstable");
629 gate_all!(crate_visibility_modifier, "`crate` visibility modifier is experimental");
630 gate_all!(const_generics, "const generics are unstable");
631 gate_all!(decl_macro, "`macro` is experimental");
632 gate_all!(box_patterns, "box pattern syntax is experimental");
633 gate_all!(exclusive_range_pattern, "exclusive range pattern syntax is experimental");
634 gate_all!(try_blocks, "`try` blocks are unstable");
635 gate_all!(label_break_value, "labels on blocks are unstable");
636 gate_all!(box_syntax, "box expression syntax is experimental; you can call `Box::new` instead");
637 // To avoid noise about type ascription in common syntax errors,
638 // only emit if it is the *only* error. (Also check it last.)
639 if parse_sess.span_diagnostic.err_count() == 0 {
640 gate_all!(type_ascription, "type ascription is experimental");
643 visit::walk_crate(&mut visitor, krate);
646 fn maybe_stage_features(span_handler: &Handler, krate: &ast::Crate, unstable: UnstableFeatures) {
647 if !unstable.is_nightly_build() {
648 for attr in krate.attrs.iter().filter(|attr| attr.check_name(sym::feature)) {
653 "`#![feature]` may not be used on the {} release channel",
654 option_env!("CFG_RELEASE_CHANNEL").unwrap_or("(unknown)")