707 lines
28 KiB
Rust
707 lines
28 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 rustc_middle::hir::map::Map;
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::TyCtxt;
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use rustc_ast::{Attribute, NestedMetaItem};
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use rustc_errors::struct_span_err;
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use rustc_hir as hir;
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use rustc_hir::def_id::LocalDefId;
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use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
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use rustc_hir::{self, HirId, Item, ItemKind, TraitItem};
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use rustc_hir::{MethodKind, Target};
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use rustc_session::lint::builtin::{CONFLICTING_REPR_HINTS, UNUSED_ATTRIBUTES};
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use rustc_session::parse::feature_err;
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use rustc_span::symbol::sym;
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use rustc_span::Span;
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pub(crate) fn target_from_impl_item<'tcx>(
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tcx: TyCtxt<'tcx>,
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impl_item: &hir::ImplItem<'_>,
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) -> Target {
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match impl_item.kind {
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hir::ImplItemKind::Const(..) => Target::AssocConst,
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hir::ImplItemKind::Fn(..) => {
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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 { ref of_trait, .. } => of_trait.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(..) => Target::AssocTy,
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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 self.tcx.sess.check_name(attr, sym::inline) {
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self.check_inline(hir_id, attr, span, target)
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} else if self.tcx.sess.check_name(attr, sym::non_exhaustive) {
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self.check_non_exhaustive(attr, span, target)
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} else if self.tcx.sess.check_name(attr, sym::marker) {
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self.check_marker(attr, span, target)
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} else if self.tcx.sess.check_name(attr, sym::target_feature) {
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self.check_target_feature(hir_id, attr, span, target)
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} else if self.tcx.sess.check_name(attr, sym::track_caller) {
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self.check_track_caller(&attr.span, attrs, span, target)
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} else if self.tcx.sess.check_name(attr, sym::doc) {
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self.check_doc_alias(attr, hir_id, target)
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} else if self.tcx.sess.check_name(attr, sym::no_link) {
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self.check_no_link(&attr, span, target)
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} else if self.tcx.sess.check_name(attr, sym::export_name) {
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self.check_export_name(&attr, span, target)
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} else {
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// lint-only checks
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if self.tcx.sess.check_name(attr, sym::cold) {
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self.check_cold(hir_id, attr, span, target);
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} else if self.tcx.sess.check_name(attr, sym::link_name) {
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self.check_link_name(hir_id, attr, span, target);
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} else if self.tcx.sess.check_name(attr, sym::link_section) {
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self.check_link_section(hir_id, attr, span, target);
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} else if self.tcx.sess.check_name(attr, sym::no_mangle) {
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self.check_no_mangle(hir_id, attr, span, target);
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}
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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 matches!(target, Target::Fn | Target::Method(_) | Target::ForeignFn) {
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self.tcx.ensure().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, hir_id);
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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 } | MethodKind::Inherent) => true,
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Target::Method(MethodKind::Trait { body: false }) | Target::ForeignFn => {
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self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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lint.build("`#[inline]` is ignored on function prototypes").emit()
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});
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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.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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lint.build("`#[inline]` is ignored on constants")
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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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"see issue #65833 <https://github.com/rust-lang/rust/issues/65833> \
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for more information",
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)
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.emit();
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});
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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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_ if self.tcx.sess.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(..) | Target::ForeignFn | Target::Closure => 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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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(
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&self,
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hir_id: HirId,
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attr: &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
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| Target::Method(MethodKind::Trait { body: true } | MethodKind::Inherent) => true,
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// FIXME: #[target_feature] was previously erroneously allowed on statements and some
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// crates used this, so only emit a warning.
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Target::Statement => {
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self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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lint.build("attribute should be applied to a function")
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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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.span_label(*span, "not a function")
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.emit();
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});
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true
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}
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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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fn check_doc_alias(&self, attr: &Attribute, hir_id: HirId, target: Target) -> bool {
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if let Some(mi) = attr.meta() {
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if let Some(list) = mi.meta_item_list() {
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for meta in list {
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if meta.has_name(sym::alias) {
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if !meta.is_value_str()
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|| meta
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.value_str()
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.map(|s| s.to_string())
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.unwrap_or_else(String::new)
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.is_empty()
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{
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self.tcx
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.sess
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.struct_span_err(
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meta.span(),
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"doc alias attribute expects a string: #[doc(alias = \"0\")]",
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)
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.emit();
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return false;
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}
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if let Some(err) = match target {
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Target::Impl => Some("implementation block"),
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Target::ForeignMod => Some("extern block"),
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Target::AssocTy => {
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let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
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let containing_item = self.tcx.hir().expect_item(parent_hir_id);
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if Target::from_item(containing_item) == Target::Impl {
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Some("type alias in implementation block")
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} else {
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None
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}
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}
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Target::AssocConst => {
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let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
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let containing_item = self.tcx.hir().expect_item(parent_hir_id);
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// We can't link to trait impl's consts.
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let err = "associated constant in trait implementation block";
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match containing_item.kind {
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ItemKind::Impl { of_trait: Some(_), .. } => Some(err),
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_ => None,
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}
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}
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_ => None,
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} {
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self.tcx
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.sess
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.struct_span_err(
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meta.span(),
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&format!("`#[doc(alias = \"...\")]` isn't allowed on {}", err),
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)
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.emit();
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}
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}
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}
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}
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}
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true
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}
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/// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid.
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fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
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match target {
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Target::Fn | Target::Method(..) | Target::ForeignFn | Target::Closure => {}
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_ => {
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// FIXME: #[cold] was previously allowed on non-functions and some crates used
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// this, so only emit a warning.
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self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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lint.build("attribute should be applied to a function")
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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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.span_label(*span, "not a function")
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.emit();
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});
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}
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}
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}
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/// Checks if `#[link_name]` is applied to an item other than a foreign function or static.
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fn check_link_name(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
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match target {
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Target::ForeignFn | Target::ForeignStatic => {}
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_ => {
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// FIXME: #[cold] was previously allowed on non-functions/statics and some crates
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// used this, so only emit a warning.
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self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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let mut diag =
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lint.build("attribute should be applied to a foreign function or static");
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diag.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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// See issue #47725
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if let Target::ForeignMod = target {
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if let Some(value) = attr.value_str() {
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diag.span_help(
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attr.span,
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&format!(r#"try `#[link(name = "{}")]` instead"#, value),
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);
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} else {
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diag.span_help(attr.span, r#"try `#[link(name = "...")]` instead"#);
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}
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}
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diag.span_label(*span, "not a foreign function or static");
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diag.emit();
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});
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}
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}
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}
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/// Checks if `#[no_link]` is applied to an `extern crate`. Returns `true` if valid.
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fn check_no_link(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
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if target == Target::ExternCrate {
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true
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} else {
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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 an `extern crate` item")
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.span_label(*span, "not an `extern crate` item")
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.emit();
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false
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}
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}
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/// Checks if `#[export_name]` is applied to a function or static. Returns `true` if valid.
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fn check_export_name(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
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match target {
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Target::Static | Target::Fn | Target::Method(..) => true,
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_ => {
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self.tcx
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.sess
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.struct_span_err(
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attr.span,
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"attribute should be applied to a function or static",
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)
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.span_label(*span, "not a function or static")
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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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|
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/// Checks if `#[link_section]` is applied to a function or static.
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fn check_link_section(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
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match target {
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Target::Static | Target::Fn | Target::Method(..) => {}
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_ => {
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// FIXME: #[link_section] was previously allowed on non-functions/statics and some
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// crates used this, so only emit a warning.
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self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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lint.build("attribute should be applied to a function or static")
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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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.span_label(*span, "not a function or static")
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.emit();
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});
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}
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}
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}
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|
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/// Checks if `#[no_mangle]` is applied to a function or static.
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fn check_no_mangle(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
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match target {
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Target::Static | Target::Fn | Target::Method(..) => {}
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_ => {
|
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// FIXME: #[no_mangle] was previously allowed on non-functions/statics and some
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// crates used this, so only emit a warning.
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self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
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lint.build("attribute should be applied to a function or static")
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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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.span_label(*span, "not a function or static")
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.emit();
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});
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}
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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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hir_id: HirId,
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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| self.tcx.sess.check_name(attr, 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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|
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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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}
|
|
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 {
|
|
self.check_attributes(l.hir_id, &l.attrs, &stmt.span, Target::Statement, None);
|
|
for attr in l.attrs.iter() {
|
|
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,
|
|
};
|
|
self.check_attributes(expr.hir_id, &expr.attrs, &expr.span, target, None);
|
|
for attr in expr.attrs.iter() {
|
|
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 };
|
|
}
|