| //! 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 crate::hir::{self, HirId, HirVec, Attribute, Item, ItemKind, TraitItem, TraitItemKind}; |
| use crate::hir::DUMMY_HIR_ID; |
| use crate::hir::def_id::DefId; |
| use crate::hir::intravisit::{self, Visitor, NestedVisitorMap}; |
| use crate::lint::builtin::UNUSED_ATTRIBUTES; |
| use crate::ty::TyCtxt; |
| use crate::ty::query::Providers; |
| |
| use std::fmt::{self, Display}; |
| use syntax::{attr, symbol::sym}; |
| use syntax_pos::Span; |
| |
| use rustc_error_codes::*; |
| |
| #[derive(Copy, Clone, PartialEq)] |
| pub(crate) enum MethodKind { |
| Trait { body: bool }, |
| Inherent, |
| } |
| |
| #[derive(Copy, Clone, PartialEq)] |
| pub(crate) enum Target { |
| ExternCrate, |
| Use, |
| Static, |
| Const, |
| Fn, |
| Closure, |
| Mod, |
| ForeignMod, |
| GlobalAsm, |
| TyAlias, |
| OpaqueTy, |
| Enum, |
| Struct, |
| Union, |
| Trait, |
| TraitAlias, |
| Impl, |
| Expression, |
| Statement, |
| AssocConst, |
| Method(MethodKind), |
| AssocTy, |
| ForeignFn, |
| ForeignStatic, |
| ForeignTy, |
| } |
| |
| impl Display for Target { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| write!(f, "{}", match *self { |
| Target::ExternCrate => "extern crate", |
| Target::Use => "use", |
| Target::Static => "static item", |
| Target::Const => "constant item", |
| Target::Fn => "function", |
| Target::Closure => "closure", |
| Target::Mod => "module", |
| Target::ForeignMod => "foreign module", |
| Target::GlobalAsm => "global asm", |
| Target::TyAlias => "type alias", |
| Target::OpaqueTy => "opaque type", |
| Target::Enum => "enum", |
| Target::Struct => "struct", |
| Target::Union => "union", |
| Target::Trait => "trait", |
| Target::TraitAlias => "trait alias", |
| Target::Impl => "item", |
| Target::Expression => "expression", |
| Target::Statement => "statement", |
| Target::AssocConst => "associated const", |
| Target::Method(_) => "method", |
| Target::AssocTy => "associated type", |
| Target::ForeignFn => "foreign function", |
| Target::ForeignStatic => "foreign static item", |
| Target::ForeignTy => "foreign type", |
| }) |
| } |
| } |
| |
| impl Target { |
| pub(crate) fn from_item(item: &Item) -> Target { |
| match item.kind { |
| ItemKind::ExternCrate(..) => Target::ExternCrate, |
| ItemKind::Use(..) => Target::Use, |
| ItemKind::Static(..) => Target::Static, |
| ItemKind::Const(..) => Target::Const, |
| ItemKind::Fn(..) => Target::Fn, |
| ItemKind::Mod(..) => Target::Mod, |
| ItemKind::ForeignMod(..) => Target::ForeignMod, |
| ItemKind::GlobalAsm(..) => Target::GlobalAsm, |
| ItemKind::TyAlias(..) => Target::TyAlias, |
| ItemKind::OpaqueTy(..) => Target::OpaqueTy, |
| ItemKind::Enum(..) => Target::Enum, |
| ItemKind::Struct(..) => Target::Struct, |
| ItemKind::Union(..) => Target::Union, |
| ItemKind::Trait(..) => Target::Trait, |
| ItemKind::TraitAlias(..) => Target::TraitAlias, |
| ItemKind::Impl(..) => Target::Impl, |
| } |
| } |
| |
| fn from_trait_item(trait_item: &TraitItem) -> Target { |
| match trait_item.kind { |
| TraitItemKind::Const(..) => Target::AssocConst, |
| TraitItemKind::Method(_, hir::TraitMethod::Required(_)) => { |
| Target::Method(MethodKind::Trait { body: false }) |
| } |
| TraitItemKind::Method(_, hir::TraitMethod::Provided(_)) => { |
| Target::Method(MethodKind::Trait { body: true }) |
| } |
| TraitItemKind::Type(..) => Target::AssocTy, |
| } |
| } |
| |
| fn from_foreign_item(foreign_item: &hir::ForeignItem) -> Target { |
| match foreign_item.kind { |
| hir::ForeignItemKind::Fn(..) => Target::ForeignFn, |
| hir::ForeignItemKind::Static(..) => Target::ForeignStatic, |
| hir::ForeignItemKind::Type => Target::ForeignTy, |
| } |
| } |
| |
| fn from_impl_item<'tcx>(tcx: TyCtxt<'tcx>, impl_item: &hir::ImplItem) -> Target { |
| match impl_item.kind { |
| hir::ImplItemKind::Const(..) => Target::AssocConst, |
| hir::ImplItemKind::Method(..) => { |
| 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(_, _, _, _, tr, _, _) => tr.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(..) | hir::ImplItemKind::OpaqueTy(..) => Target::AssocTy, |
| } |
| } |
| } |
| |
| struct CheckAttrVisitor<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| } |
| |
| impl CheckAttrVisitor<'tcx> { |
| /// Checks any attribute. |
| fn check_attributes( |
| &self, |
| hir_id: HirId, |
| attrs: &HirVec<Attribute>, |
| span: &Span, |
| target: Target, |
| item: Option<&Item>, |
| ) { |
| let mut is_valid = true; |
| for attr in attrs { |
| is_valid &= if attr.check_name(sym::inline) { |
| self.check_inline(hir_id, attr, span, target) |
| } else if attr.check_name(sym::non_exhaustive) { |
| self.check_non_exhaustive(attr, span, target) |
| } else if attr.check_name(sym::marker) { |
| self.check_marker(attr, span, target) |
| } else if attr.check_name(sym::target_feature) { |
| self.check_target_feature(attr, span, target) |
| } else if attr.check_name(sym::track_caller) { |
| self.check_track_caller(&attr.span, attrs, span, target) |
| } else { |
| true |
| }; |
| } |
| |
| if !is_valid { |
| return; |
| } |
| |
| if target == Target::Fn { |
| self.tcx.codegen_fn_attrs(self.tcx.hir().local_def_id(hir_id)); |
| } |
| |
| self.check_repr(attrs, span, target, item); |
| 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 }) |
| | Target::Method(MethodKind::Inherent) => true, |
| Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => { |
| self.tcx.struct_span_lint_hir( |
| UNUSED_ATTRIBUTES, |
| hir_id, |
| attr.span, |
| "`#[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, |
| "`#[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("for more information, see issue #65833 \ |
| <https://github.com/rust-lang/rust/issues/65833>") |
| .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: &HirVec<Attribute>, |
| span: &Span, |
| target: Target, |
| ) -> bool { |
| match target { |
| Target::Fn if attr::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(MethodKind::Inherent) => true, |
| Target::Method(_) => { |
| struct_span_err!( |
| self.tcx.sess, |
| *attr_span, |
| E0738, |
| "`#[track_caller]` may not be used on trait methods", |
| ).emit(); |
| false |
| } |
| _ => { |
| 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 }) |
| | Target::Method(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 |
| }, |
| } |
| } |
| |
| /// Checks if the `#[repr]` attributes on `item` are valid. |
| fn check_repr( |
| &self, |
| attrs: &HirVec<Attribute>, |
| span: &Span, |
| target: Target, |
| item: Option<&Item>, |
| ) { |
| // 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| attr.check_name(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::i8 | sym::u8 | sym::i16 | sym::u16 | |
| sym::i32 | sym::u32 | sym::i64 | sym::u64 | |
| 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>). |
| if is_transparent && hints.len() > 1 { |
| let hint_spans: Vec<_> = hint_spans.clone().collect(); |
| span_err!(self.tcx.sess, hint_spans, E0692, |
| "transparent {} cannot have other repr hints", target); |
| } |
| // 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))) { |
| let hint_spans: Vec<_> = hint_spans.collect(); |
| span_warn!(self.tcx.sess, hint_spans, E0566, |
| "conflicting representation hints"); |
| } |
| } |
| |
| 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 attr.check_name(sym::inline) { |
| self.check_inline(DUMMY_HIR_ID, attr, &stmt.span, Target::Statement); |
| } |
| if attr.check_name(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 attr.check_name(sym::inline) { |
| self.check_inline(DUMMY_HIR_ID, attr, &expr.span, target); |
| } |
| if attr.check_name(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", |
| ); |
| } |
| } |
| } |
| |
| fn check_used(&self, attrs: &HirVec<Attribute>, target: Target) { |
| for attr in attrs { |
| if attr.check_name(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> { |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::OnlyBodies(&self.tcx.hir()) |
| } |
| |
| fn visit_item(&mut self, item: &'tcx Item) { |
| 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) { |
| 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) { |
| 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) { |
| 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) { |
| self.check_stmt_attributes(stmt); |
| intravisit::walk_stmt(self, stmt) |
| } |
| |
| fn visit_expr(&mut self, expr: &'tcx hir::Expr) { |
| 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: DefId) { |
| 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 |
| }; |
| } |
