583 lines
20 KiB
Rust
583 lines
20 KiB
Rust
//! This module implements some validity checks for attributes.
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//! In particular it verifies that `#[inline]` and `#[repr]` attributes are
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//! attached to items that actually support them and if there are
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//! conflicts between multiple such attributes attached to the same
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//! item.
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use crate::hir::intravisit::{self, NestedVisitorMap, Visitor};
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use crate::lint::builtin::UNUSED_ATTRIBUTES;
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use crate::ty::query::Providers;
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use crate::ty::TyCtxt;
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use errors::struct_span_err;
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use rustc_error_codes::*;
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use rustc_hir as hir;
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use rustc_hir::def_id::DefId;
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use rustc_hir::DUMMY_HIR_ID;
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use rustc_hir::{self, HirId, Item, ItemKind, TraitItem, TraitItemKind};
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use rustc_span::symbol::sym;
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use rustc_span::Span;
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use syntax::ast::Attribute;
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use syntax::attr;
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use std::fmt::{self, Display};
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#[derive(Copy, Clone, PartialEq)]
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pub(crate) enum MethodKind {
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Trait { body: bool },
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Inherent,
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}
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#[derive(Copy, Clone, PartialEq)]
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pub(crate) enum Target {
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ExternCrate,
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Use,
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Static,
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Const,
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Fn,
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Closure,
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Mod,
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ForeignMod,
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GlobalAsm,
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TyAlias,
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OpaqueTy,
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Enum,
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Struct,
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Union,
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Trait,
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TraitAlias,
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Impl,
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Expression,
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Statement,
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AssocConst,
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Method(MethodKind),
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AssocTy,
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ForeignFn,
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ForeignStatic,
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ForeignTy,
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}
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impl Display for Target {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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write!(
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f,
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"{}",
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match *self {
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Target::ExternCrate => "extern crate",
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Target::Use => "use",
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Target::Static => "static item",
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Target::Const => "constant item",
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Target::Fn => "function",
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Target::Closure => "closure",
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Target::Mod => "module",
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Target::ForeignMod => "foreign module",
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Target::GlobalAsm => "global asm",
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Target::TyAlias => "type alias",
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Target::OpaqueTy => "opaque type",
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Target::Enum => "enum",
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Target::Struct => "struct",
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Target::Union => "union",
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Target::Trait => "trait",
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Target::TraitAlias => "trait alias",
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Target::Impl => "item",
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Target::Expression => "expression",
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Target::Statement => "statement",
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Target::AssocConst => "associated const",
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Target::Method(_) => "method",
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Target::AssocTy => "associated type",
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Target::ForeignFn => "foreign function",
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Target::ForeignStatic => "foreign static item",
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Target::ForeignTy => "foreign type",
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}
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)
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}
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}
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impl Target {
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pub(crate) fn from_item(item: &Item<'_>) -> Target {
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match item.kind {
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ItemKind::ExternCrate(..) => Target::ExternCrate,
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ItemKind::Use(..) => Target::Use,
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ItemKind::Static(..) => Target::Static,
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ItemKind::Const(..) => Target::Const,
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ItemKind::Fn(..) => Target::Fn,
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ItemKind::Mod(..) => Target::Mod,
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ItemKind::ForeignMod(..) => Target::ForeignMod,
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ItemKind::GlobalAsm(..) => Target::GlobalAsm,
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ItemKind::TyAlias(..) => Target::TyAlias,
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ItemKind::OpaqueTy(..) => Target::OpaqueTy,
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ItemKind::Enum(..) => Target::Enum,
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ItemKind::Struct(..) => Target::Struct,
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ItemKind::Union(..) => Target::Union,
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ItemKind::Trait(..) => Target::Trait,
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ItemKind::TraitAlias(..) => Target::TraitAlias,
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ItemKind::Impl(..) => Target::Impl,
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}
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}
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fn from_trait_item(trait_item: &TraitItem<'_>) -> Target {
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match trait_item.kind {
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TraitItemKind::Const(..) => Target::AssocConst,
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TraitItemKind::Method(_, hir::TraitMethod::Required(_)) => {
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Target::Method(MethodKind::Trait { body: false })
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}
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TraitItemKind::Method(_, hir::TraitMethod::Provided(_)) => {
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Target::Method(MethodKind::Trait { body: true })
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}
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TraitItemKind::Type(..) => Target::AssocTy,
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}
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}
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fn from_foreign_item(foreign_item: &hir::ForeignItem<'_>) -> Target {
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match foreign_item.kind {
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hir::ForeignItemKind::Fn(..) => Target::ForeignFn,
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hir::ForeignItemKind::Static(..) => Target::ForeignStatic,
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hir::ForeignItemKind::Type => Target::ForeignTy,
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}
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}
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fn from_impl_item<'tcx>(tcx: TyCtxt<'tcx>, impl_item: &hir::ImplItem<'_>) -> Target {
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match impl_item.kind {
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hir::ImplItemKind::Const(..) => Target::AssocConst,
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hir::ImplItemKind::Method(..) => {
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let parent_hir_id = tcx.hir().get_parent_item(impl_item.hir_id);
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let containing_item = tcx.hir().expect_item(parent_hir_id);
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let containing_impl_is_for_trait = match &containing_item.kind {
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hir::ItemKind::Impl(_, _, _, _, tr, _, _) => tr.is_some(),
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_ => bug!("parent of an ImplItem must be an Impl"),
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};
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if containing_impl_is_for_trait {
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Target::Method(MethodKind::Trait { body: true })
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} else {
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Target::Method(MethodKind::Inherent)
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}
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}
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hir::ImplItemKind::TyAlias(..) | hir::ImplItemKind::OpaqueTy(..) => Target::AssocTy,
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}
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}
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}
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struct CheckAttrVisitor<'tcx> {
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tcx: TyCtxt<'tcx>,
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}
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impl CheckAttrVisitor<'tcx> {
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/// Checks any attribute.
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fn check_attributes(
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&self,
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hir_id: HirId,
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attrs: &'hir [Attribute],
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span: &Span,
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target: Target,
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item: Option<&Item<'_>>,
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) {
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let mut is_valid = true;
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for attr in attrs {
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is_valid &= if attr.check_name(sym::inline) {
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self.check_inline(hir_id, attr, span, target)
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} else if attr.check_name(sym::non_exhaustive) {
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self.check_non_exhaustive(attr, span, target)
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} else if attr.check_name(sym::marker) {
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self.check_marker(attr, span, target)
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} else if attr.check_name(sym::target_feature) {
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self.check_target_feature(attr, span, target)
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} else if attr.check_name(sym::track_caller) {
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self.check_track_caller(&attr.span, attrs, span, target)
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} else {
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true
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};
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}
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if !is_valid {
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return;
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}
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if target == Target::Fn {
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self.tcx.codegen_fn_attrs(self.tcx.hir().local_def_id(hir_id));
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}
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self.check_repr(attrs, span, target, item);
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self.check_used(attrs, target);
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}
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/// Checks if an `#[inline]` is applied to a function or a closure. Returns `true` if valid.
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fn check_inline(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) -> bool {
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match target {
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Target::Fn
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| Target::Closure
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| Target::Method(MethodKind::Trait { body: true })
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| Target::Method(MethodKind::Inherent) => true,
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Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
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self.tcx
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.struct_span_lint_hir(
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UNUSED_ATTRIBUTES,
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hir_id,
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attr.span,
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"`#[inline]` is ignored on function prototypes",
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)
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.emit();
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true
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}
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// FIXME(#65833): We permit associated consts to have an `#[inline]` attribute with
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// just a lint, because we previously erroneously allowed it and some crates used it
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// accidentally, to to be compatible with crates depending on them, we can't throw an
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// error here.
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Target::AssocConst => {
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self.tcx
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.struct_span_lint_hir(
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UNUSED_ATTRIBUTES,
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hir_id,
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attr.span,
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"`#[inline]` is ignored on constants",
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)
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.warn(
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"this was previously accepted by the compiler but is \
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being phased out; it will become a hard error in \
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a future release!",
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)
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.note(
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"for more information, see issue #65833 \
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<https://github.com/rust-lang/rust/issues/65833>",
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)
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.emit();
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true
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}
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_ => {
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struct_span_err!(
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self.tcx.sess,
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attr.span,
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E0518,
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"attribute should be applied to function or closure",
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)
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.span_label(*span, "not a function or closure")
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.emit();
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false
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}
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}
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}
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/// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid.
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fn check_track_caller(
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&self,
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attr_span: &Span,
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attrs: &'hir [Attribute],
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span: &Span,
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target: Target,
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) -> bool {
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match target {
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Target::Fn if attr::contains_name(attrs, sym::naked) => {
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struct_span_err!(
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self.tcx.sess,
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*attr_span,
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E0736,
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"cannot use `#[track_caller]` with `#[naked]`",
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)
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.emit();
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false
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}
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Target::Fn | Target::Method(MethodKind::Inherent) => true,
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Target::Method(_) => {
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struct_span_err!(
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self.tcx.sess,
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*attr_span,
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E0738,
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"`#[track_caller]` may not be used on trait methods",
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)
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.emit();
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false
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}
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_ => {
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struct_span_err!(
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self.tcx.sess,
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*attr_span,
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E0739,
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"attribute should be applied to function"
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)
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.span_label(*span, "not a function")
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.emit();
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false
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}
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}
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}
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/// Checks if the `#[non_exhaustive]` attribute on an `item` is valid. Returns `true` if valid.
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fn check_non_exhaustive(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
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match target {
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Target::Struct | Target::Enum => true,
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_ => {
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struct_span_err!(
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self.tcx.sess,
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attr.span,
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E0701,
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"attribute can only be applied to a struct or enum"
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)
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.span_label(*span, "not a struct or enum")
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.emit();
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false
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}
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}
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}
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/// Checks if the `#[marker]` attribute on an `item` is valid. Returns `true` if valid.
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fn check_marker(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
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match target {
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Target::Trait => true,
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_ => {
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self.tcx
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.sess
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.struct_span_err(attr.span, "attribute can only be applied to a trait")
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.span_label(*span, "not a trait")
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.emit();
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false
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}
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}
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}
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/// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid.
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fn check_target_feature(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
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match target {
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Target::Fn
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| Target::Method(MethodKind::Trait { body: true })
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| Target::Method(MethodKind::Inherent) => true,
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_ => {
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self.tcx
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.sess
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.struct_span_err(attr.span, "attribute should be applied to a function")
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.span_label(*span, "not a function")
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.emit();
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false
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}
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}
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}
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/// Checks if the `#[repr]` attributes on `item` are valid.
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fn check_repr(
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&self,
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attrs: &'hir [Attribute],
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span: &Span,
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target: Target,
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item: Option<&Item<'_>>,
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) {
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// Extract the names of all repr hints, e.g., [foo, bar, align] for:
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// ```
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// #[repr(foo)]
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// #[repr(bar, align(8))]
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// ```
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let hints: Vec<_> = attrs
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.iter()
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.filter(|attr| attr.check_name(sym::repr))
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.filter_map(|attr| attr.meta_item_list())
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.flatten()
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.collect();
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let mut int_reprs = 0;
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let mut is_c = false;
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let mut is_simd = false;
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let mut is_transparent = false;
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for hint in &hints {
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let (article, allowed_targets) = match hint.name_or_empty() {
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name @ sym::C | name @ sym::align => {
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is_c |= name == sym::C;
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match target {
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Target::Struct | Target::Union | Target::Enum => continue,
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_ => ("a", "struct, enum, or union"),
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}
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}
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sym::packed => {
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if target != Target::Struct && target != Target::Union {
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("a", "struct or union")
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} else {
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continue;
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}
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}
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sym::simd => {
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is_simd = true;
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if target != Target::Struct { ("a", "struct") } else { continue }
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}
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sym::transparent => {
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is_transparent = true;
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match target {
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Target::Struct | Target::Union | Target::Enum => continue,
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_ => ("a", "struct, enum, or union"),
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}
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}
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sym::i8
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| sym::u8
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| sym::i16
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| sym::u16
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| sym::i32
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|
| sym::u32
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| sym::i64
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| sym::u64
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| sym::isize
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| sym::usize => {
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int_reprs += 1;
|
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if target != Target::Enum { ("an", "enum") } else { continue }
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}
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_ => continue,
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};
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self.emit_repr_error(
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hint.span(),
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*span,
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&format!("attribute should be applied to {}", allowed_targets),
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&format!("not {} {}", article, allowed_targets),
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)
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}
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|
|
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// Just point at all repr hints if there are any incompatibilities.
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// This is not ideal, but tracking precisely which ones are at fault is a huge hassle.
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let hint_spans = hints.iter().map(|hint| hint.span());
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|
|
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// Error on repr(transparent, <anything else>).
|
|
if is_transparent && hints.len() > 1 {
|
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let hint_spans: Vec<_> = hint_spans.clone().collect();
|
|
struct_span_err!(
|
|
self.tcx.sess,
|
|
hint_spans,
|
|
E0692,
|
|
"transparent {} cannot have other repr hints",
|
|
target
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)
|
|
.emit();
|
|
}
|
|
// Warn on repr(u8, u16), repr(C, simd), and c-like-enum-repr(C, u8)
|
|
if (int_reprs > 1)
|
|
|| (is_simd && is_c)
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|
|| (int_reprs == 1 && is_c && item.map_or(false, |item| is_c_like_enum(item)))
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|
{
|
|
struct_span_err!(
|
|
self.tcx.sess,
|
|
hint_spans.collect::<Vec<Span>>(),
|
|
E0566,
|
|
"conflicting representation hints",
|
|
)
|
|
.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 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: &'hir [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<'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: 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 };
|
|
}
|