1 //! Unsafety checker: every impl either implements a trait defined in this
2 //! crate or pertains to a type defined in this crate.
4 use rustc_errors::struct_span_err;
6 use rustc_hir::itemlikevisit::ItemLikeVisitor;
7 use rustc_hir::Unsafety;
8 use rustc_middle::ty::TyCtxt;
10 pub fn check(tcx: TyCtxt<'_>) {
11 let mut unsafety = UnsafetyChecker { tcx };
12 tcx.hir().visit_all_item_likes(&mut unsafety);
15 struct UnsafetyChecker<'tcx> {
19 impl<'tcx> UnsafetyChecker<'tcx> {
20 fn check_unsafety_coherence(
23 impl_generics: Option<&hir::Generics<'_>>,
24 unsafety: hir::Unsafety,
25 polarity: hir::ImplPolarity,
27 if let Some(trait_ref) = self.tcx.impl_trait_ref(item.def_id) {
28 let trait_def = self.tcx.trait_def(trait_ref.def_id);
29 let unsafe_attr = impl_generics.and_then(|generics| {
30 generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle")
32 match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
33 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
38 "implementing the trait `{}` is not unsafe",
39 trait_ref.print_only_trait_path()
44 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
49 "the trait `{}` requires an `unsafe impl` declaration",
50 trait_ref.print_only_trait_path()
59 hir::ImplPolarity::Positive,
65 "requires an `unsafe impl` declaration due to `#[{}]` attribute",
71 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative(_)) => {
72 // Reported in AST validation
73 self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
75 (_, _, Unsafety::Normal, hir::ImplPolarity::Negative(_))
76 | (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive)
77 | (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive)
78 | (Unsafety::Normal, None, Unsafety::Normal, _) => {
86 impl<'tcx> ItemLikeVisitor<'_> for UnsafetyChecker<'tcx> {
87 fn visit_item(&mut self, item: &hir::Item<'_>) {
88 if let hir::ItemKind::Impl(ref impl_) = item.kind {
89 self.check_unsafety_coherence(
91 Some(&impl_.generics),
98 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
100 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
102 fn visit_foreign_item(&mut self, _foreign_item: &hir::ForeignItem<'_>) {}