diff options
Diffstat (limited to 'compiler/rustc_passes/src/check_attr.rs')
| -rw-r--r-- | compiler/rustc_passes/src/check_attr.rs | 527 |
1 files changed, 527 insertions, 0 deletions
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs new file mode 100644 index 00000000000..832cde86d0b --- /dev/null +++ b/compiler/rustc_passes/src/check_attr.rs @@ -0,0 +1,527 @@ +//! This module implements some validity checks for attributes. +//! In particular it verifies that `#[inline]` and `#[repr]` attributes are +//! attached to items that actually support them and if there are +//! conflicts between multiple such attributes attached to the same +//! item. + +use rustc_middle::hir::map::Map; +use rustc_middle::ty::query::Providers; +use rustc_middle::ty::TyCtxt; + +use rustc_ast::{Attribute, NestedMetaItem}; +use rustc_errors::struct_span_err; +use rustc_hir as hir; +use rustc_hir::def_id::LocalDefId; +use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor}; +use rustc_hir::{self, HirId, Item, ItemKind, TraitItem}; +use rustc_hir::{MethodKind, Target}; +use rustc_session::lint::builtin::{CONFLICTING_REPR_HINTS, UNUSED_ATTRIBUTES}; +use rustc_session::parse::feature_err; +use rustc_span::symbol::sym; +use rustc_span::Span; + +pub(crate) fn target_from_impl_item<'tcx>( + tcx: TyCtxt<'tcx>, + impl_item: &hir::ImplItem<'_>, +) -> Target { + match impl_item.kind { + hir::ImplItemKind::Const(..) => Target::AssocConst, + hir::ImplItemKind::Fn(..) => { + let parent_hir_id = tcx.hir().get_parent_item(impl_item.hir_id); + let containing_item = tcx.hir().expect_item(parent_hir_id); + let containing_impl_is_for_trait = match &containing_item.kind { + hir::ItemKind::Impl { ref of_trait, .. } => of_trait.is_some(), + _ => bug!("parent of an ImplItem must be an Impl"), + }; + if containing_impl_is_for_trait { + Target::Method(MethodKind::Trait { body: true }) + } else { + Target::Method(MethodKind::Inherent) + } + } + hir::ImplItemKind::TyAlias(..) => Target::AssocTy, + } +} + +struct CheckAttrVisitor<'tcx> { + tcx: TyCtxt<'tcx>, +} + +impl CheckAttrVisitor<'tcx> { + /// Checks any attribute. + fn check_attributes( + &self, + hir_id: HirId, + attrs: &'hir [Attribute], + span: &Span, + target: Target, + item: Option<&Item<'_>>, + ) { + let mut is_valid = true; + for attr in attrs { + is_valid &= if self.tcx.sess.check_name(attr, sym::inline) { + self.check_inline(hir_id, attr, span, target) + } else if self.tcx.sess.check_name(attr, sym::non_exhaustive) { + self.check_non_exhaustive(attr, span, target) + } else if self.tcx.sess.check_name(attr, sym::marker) { + self.check_marker(attr, span, target) + } else if self.tcx.sess.check_name(attr, sym::target_feature) { + self.check_target_feature(attr, span, target) + } else if self.tcx.sess.check_name(attr, sym::track_caller) { + self.check_track_caller(&attr.span, attrs, span, target) + } else if self.tcx.sess.check_name(attr, sym::doc) { + self.check_doc_alias(attr, hir_id, target) + } else { + true + }; + } + + if !is_valid { + return; + } + + if matches!(target, Target::Fn | Target::Method(_) | Target::ForeignFn) { + self.tcx.ensure().codegen_fn_attrs(self.tcx.hir().local_def_id(hir_id)); + } + + self.check_repr(attrs, span, target, item, hir_id); + self.check_used(attrs, target); + } + + /// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid. + fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) -> bool { + match target { + Target::Fn + | Target::Closure + | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, + Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => { + self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| { + lint.build("`#[inline]` is ignored on function prototypes").emit() + }); + true + } + // FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with + // just a lint, because we previously erroneously allowed it and some crates used it + // accidentally, to to be compatible with crates depending on them, we can't throw an + // error here. + Target::AssocConst => { + self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| { + lint.build("`#[inline]` is ignored on constants") + .warn( + "this was previously accepted by the compiler but is \ + being phased out; it will become a hard error in \ + a future release!", + ) + .note( + "see issue #65833 <https://github.com/rust-lang/rust/issues/65833> \ + for more information", + ) + .emit(); + }); + true + } + _ => { + struct_span_err!( + self.tcx.sess, + attr.span, + E0518, + "attribute should be applied to function or closure", + ) + .span_label(*span, "not a function or closure") + .emit(); + false + } + } + } + + /// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid. + fn check_track_caller( + &self, + attr_span: &Span, + attrs: &'hir [Attribute], + span: &Span, + target: Target, + ) -> bool { + match target { + _ if self.tcx.sess.contains_name(attrs, sym::naked) => { + struct_span_err!( + self.tcx.sess, + *attr_span, + E0736, + "cannot use `#[track_caller]` with `#[naked]`", + ) + .emit(); + false + } + Target::Fn | Target::Method(..) | Target::ForeignFn => true, + _ => { + struct_span_err!( + self.tcx.sess, + *attr_span, + E0739, + "attribute should be applied to function" + ) + .span_label(*span, "not a function") + .emit(); + false + } + } + } + + /// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid. + fn check_non_exhaustive(&self, attr: &Attribute, span: &Span, target: Target) -> bool { + match target { + Target::Struct | Target::Enum => true, + _ => { + struct_span_err!( + self.tcx.sess, + attr.span, + E0701, + "attribute can only be applied to a struct or enum" + ) + .span_label(*span, "not a struct or enum") + .emit(); + false + } + } + } + + /// Checks if the `#[marker]` attribute on an `item` is valid. Returns `true` if valid. + fn check_marker(&self, attr: &Attribute, span: &Span, target: Target) -> bool { + match target { + Target::Trait => true, + _ => { + self.tcx + .sess + .struct_span_err(attr.span, "attribute can only be applied to a trait") + .span_label(*span, "not a trait") + .emit(); + false + } + } + } + + /// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid. + fn check_target_feature(&self, attr: &Attribute, span: &Span, target: Target) -> bool { + match target { + Target::Fn + | Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true, + _ => { + self.tcx + .sess + .struct_span_err(attr.span, "attribute should be applied to a function") + .span_label(*span, "not a function") + .emit(); + false + } + } + } + + fn check_doc_alias(&self, attr: &Attribute, hir_id: HirId, target: Target) -> bool { + if let Some(mi) = attr.meta() { + if let Some(list) = mi.meta_item_list() { + for meta in list { + if meta.has_name(sym::alias) { + if !meta.is_value_str() + || meta + .value_str() + .map(|s| s.to_string()) + .unwrap_or_else(String::new) + .is_empty() + { + self.tcx + .sess + .struct_span_err( + meta.span(), + "doc alias attribute expects a string: #[doc(alias = \"0\")]", + ) + .emit(); + return false; + } + if let Some(err) = match target { + Target::Impl => Some("implementation block"), + Target::ForeignMod => Some("extern block"), + Target::AssocTy => { + let parent_hir_id = self.tcx.hir().get_parent_item(hir_id); + let containing_item = self.tcx.hir().expect_item(parent_hir_id); + if Target::from_item(containing_item) == Target::Impl { + Some("type alias in implementation block") + } else { + None + } + } + _ => None, + } { + self.tcx + .sess + .struct_span_err( + meta.span(), + &format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err,), + ) + .emit(); + } + } + } + } + } + true + } + + /// Checks if the `#[repr]` attributes on `item` are valid. + fn check_repr( + &self, + attrs: &'hir [Attribute], + span: &Span, + target: Target, + item: Option<&Item<'_>>, + hir_id: HirId, + ) { + // Extract the names of all repr hints, e.g., [foo, bar, align] for: + // ``` + // #[repr(foo)] + // #[repr(bar, align(8))] + // ``` + let hints: Vec<_> = attrs + .iter() + .filter(|attr| self.tcx.sess.check_name(attr, sym::repr)) + .filter_map(|attr| attr.meta_item_list()) + .flatten() + .collect(); + + let mut int_reprs = 0; + let mut is_c = false; + let mut is_simd = false; + let mut is_transparent = false; + + for hint in &hints { + let (article, allowed_targets) = match hint.name_or_empty() { + name @ sym::C | name @ sym::align => { + is_c |= name == sym::C; + match target { + Target::Struct | Target::Union | Target::Enum => continue, + _ => ("a", "struct, enum, or union"), + } + } + sym::packed => { + if target != Target::Struct && target != Target::Union { + ("a", "struct or union") + } else { + continue; + } + } + sym::simd => { + is_simd = true; + if target != Target::Struct { ("a", "struct") } else { continue } + } + sym::transparent => { + is_transparent = true; + match target { + Target::Struct | Target::Union | Target::Enum => continue, + _ => ("a", "struct, enum, or union"), + } + } + sym::no_niche => { + if !self.tcx.features().enabled(sym::no_niche) { + feature_err( + &self.tcx.sess.parse_sess, + sym::no_niche, + hint.span(), + "the attribute `repr(no_niche)` is currently unstable", + ) + .emit(); + } + match target { + Target::Struct | Target::Enum => continue, + _ => ("a", "struct or enum"), + } + } + sym::i8 + | sym::u8 + | sym::i16 + | sym::u16 + | sym::i32 + | sym::u32 + | sym::i64 + | sym::u64 + | sym::i128 + | sym::u128 + | sym::isize + | sym::usize => { + int_reprs += 1; + if target != Target::Enum { ("an", "enum") } else { continue } + } + _ => continue, + }; + self.emit_repr_error( + hint.span(), + *span, + &format!("attribute should be applied to {}", allowed_targets), + &format!("not {} {}", article, allowed_targets), + ) + } + + // Just point at all repr hints if there are any incompatibilities. + // This is not ideal, but tracking precisely which ones are at fault is a huge hassle. + let hint_spans = hints.iter().map(|hint| hint.span()); + + // Error on repr(transparent, <anything else apart from no_niche>). + let non_no_niche = |hint: &&NestedMetaItem| hint.name_or_empty() != sym::no_niche; + let non_no_niche_count = hints.iter().filter(non_no_niche).count(); + if is_transparent && non_no_niche_count > 1 { + let hint_spans: Vec<_> = hint_spans.clone().collect(); + struct_span_err!( + self.tcx.sess, + hint_spans, + E0692, + "transparent {} cannot have other repr hints", + target + ) + .emit(); + } + // Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8) + if (int_reprs > 1) + || (is_simd && is_c) + || (int_reprs == 1 && is_c && item.map_or(false, |item| is_c_like_enum(item))) + { + self.tcx.struct_span_lint_hir( + CONFLICTING_REPR_HINTS, + hir_id, + hint_spans.collect::<Vec<Span>>(), + |lint| { + lint.build("conflicting representation hints") + .code(rustc_errors::error_code!(E0566)) + .emit(); + }, + ); + } + } + + fn emit_repr_error( + &self, + hint_span: Span, + label_span: Span, + hint_message: &str, + label_message: &str, + ) { + struct_span_err!(self.tcx.sess, hint_span, E0517, "{}", hint_message) + .span_label(label_span, label_message) + .emit(); + } + + fn check_stmt_attributes(&self, stmt: &hir::Stmt<'_>) { + // When checking statements ignore expressions, they will be checked later + if let hir::StmtKind::Local(ref l) = stmt.kind { + for attr in l.attrs.iter() { + if self.tcx.sess.check_name(attr, sym::inline) { + self.check_inline(l.hir_id, attr, &stmt.span, Target::Statement); + } + if self.tcx.sess.check_name(attr, sym::repr) { + self.emit_repr_error( + attr.span, + stmt.span, + "attribute should not be applied to a statement", + "not a struct, enum, or union", + ); + } + } + } + } + + fn check_expr_attributes(&self, expr: &hir::Expr<'_>) { + let target = match expr.kind { + hir::ExprKind::Closure(..) => Target::Closure, + _ => Target::Expression, + }; + for attr in expr.attrs.iter() { + if self.tcx.sess.check_name(attr, sym::inline) { + self.check_inline(expr.hir_id, attr, &expr.span, target); + } + if self.tcx.sess.check_name(attr, sym::repr) { + self.emit_repr_error( + attr.span, + expr.span, + "attribute should not be applied to an expression", + "not defining a struct, enum, or union", + ); + } + } + if target == Target::Closure { + self.tcx.ensure().codegen_fn_attrs(self.tcx.hir().local_def_id(expr.hir_id)); + } + } + + fn check_used(&self, attrs: &'hir [Attribute], target: Target) { + for attr in attrs { + if self.tcx.sess.check_name(attr, sym::used) && target != Target::Static { + self.tcx + .sess + .span_err(attr.span, "attribute must be applied to a `static` variable"); + } + } + } +} + +impl Visitor<'tcx> for CheckAttrVisitor<'tcx> { + type Map = Map<'tcx>; + + fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { + NestedVisitorMap::OnlyBodies(self.tcx.hir()) + } + + fn visit_item(&mut self, item: &'tcx Item<'tcx>) { + let target = Target::from_item(item); + self.check_attributes(item.hir_id, item.attrs, &item.span, target, Some(item)); + intravisit::walk_item(self, item) + } + + fn visit_trait_item(&mut self, trait_item: &'tcx TraitItem<'tcx>) { + let target = Target::from_trait_item(trait_item); + self.check_attributes(trait_item.hir_id, &trait_item.attrs, &trait_item.span, target, None); + intravisit::walk_trait_item(self, trait_item) + } + + fn visit_foreign_item(&mut self, f_item: &'tcx hir::ForeignItem<'tcx>) { + let target = Target::from_foreign_item(f_item); + self.check_attributes(f_item.hir_id, &f_item.attrs, &f_item.span, target, None); + intravisit::walk_foreign_item(self, f_item) + } + + fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) { + let target = target_from_impl_item(self.tcx, impl_item); + self.check_attributes(impl_item.hir_id, &impl_item.attrs, &impl_item.span, target, None); + intravisit::walk_impl_item(self, impl_item) + } + + fn visit_stmt(&mut self, stmt: &'tcx hir::Stmt<'tcx>) { + self.check_stmt_attributes(stmt); + intravisit::walk_stmt(self, stmt) + } + + fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) { + self.check_expr_attributes(expr); + intravisit::walk_expr(self, expr) + } +} + +fn is_c_like_enum(item: &Item<'_>) -> bool { + if let ItemKind::Enum(ref def, _) = item.kind { + for variant in def.variants { + match variant.data { + hir::VariantData::Unit(..) => { /* continue */ } + _ => return false, + } + } + true + } else { + false + } +} + +fn check_mod_attrs(tcx: TyCtxt<'_>, module_def_id: LocalDefId) { + tcx.hir() + .visit_item_likes_in_module(module_def_id, &mut CheckAttrVisitor { tcx }.as_deep_visitor()); +} + +pub(crate) fn provide(providers: &mut Providers) { + *providers = Providers { check_mod_attrs, ..*providers }; +} |