1 //! Unsafety checker: every impl either implements a trait defined in this
2 //! crate or pertains to a type defined in this crate.
5 use rustc_errors::struct_span_err;
7 use rustc_hir::itemlikevisit::ItemLikeVisitor;
8 use rustc_hir::Unsafety;
10 pub fn check(tcx: TyCtxt<'_>) {
11 let mut unsafety = UnsafetyChecker { tcx };
12 tcx.hir().krate().visit_all_item_likes(&mut unsafety);
15 struct UnsafetyChecker<'tcx> {
19 impl UnsafetyChecker<'tcx> {
20 fn check_unsafety_coherence(
22 item: &'v hir::Item<'v>,
23 impl_generics: Option<&hir::Generics<'_>>,
24 unsafety: hir::Unsafety,
25 polarity: hir::ImplPolarity,
27 let local_did = self.tcx.hir().local_def_id(item.hir_id);
28 if let Some(trait_ref) = self.tcx.impl_trait_ref(local_did) {
29 let trait_def = self.tcx.trait_def(trait_ref.def_id);
30 let unsafe_attr = impl_generics.and_then(|generics| {
31 generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle")
33 match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
34 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
39 "implementing the trait `{}` is not unsafe",
40 trait_ref.print_only_trait_path()
45 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
50 "the trait `{}` requires an `unsafe impl` declaration",
51 trait_ref.print_only_trait_path()
60 hir::ImplPolarity::Positive,
66 "requires an `unsafe impl` declaration due to `#[{}]` attribute",
72 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative) => {
73 // Reported in AST validation
74 self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
76 (_, _, Unsafety::Normal, hir::ImplPolarity::Negative)
77 | (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive)
78 | (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive)
79 | (Unsafety::Normal, None, Unsafety::Normal, _) => {
87 impl ItemLikeVisitor<'v> for UnsafetyChecker<'tcx> {
88 fn visit_item(&mut self, item: &'v hir::Item<'v>) {
89 if let hir::ItemKind::Impl { unsafety, polarity, ref generics, .. } = item.kind {
90 self.check_unsafety_coherence(item, Some(generics), unsafety, polarity);
94 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
96 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}