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::def::DefKind;
7 use rustc_hir::Unsafety;
8 use rustc_middle::ty::TyCtxt;
9 use rustc_span::def_id::LocalDefId;
11 pub(super) fn check_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
12 debug_assert!(matches!(tcx.def_kind(def_id), DefKind::Impl));
13 let item = tcx.hir().expect_item(def_id);
14 let hir::ItemKind::Impl(ref impl_) = item.kind else { bug!() };
16 if let Some(trait_ref) = tcx.impl_trait_ref(item.def_id) {
17 let trait_def = tcx.trait_def(trait_ref.def_id);
19 impl_.generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle");
20 match (trait_def.unsafety, unsafe_attr, impl_.unsafety, impl_.polarity) {
21 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
26 "implementing the trait `{}` is not unsafe",
27 trait_ref.print_only_trait_path()
32 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
37 "the trait `{}` requires an `unsafe impl` declaration",
38 trait_ref.print_only_trait_path()
43 (Unsafety::Normal, Some(attr_name), Unsafety::Normal, hir::ImplPolarity::Positive) => {
48 "requires an `unsafe impl` declaration due to `#[{}]` attribute",
54 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative(_)) => {
55 // Reported in AST validation
56 tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
58 (_, _, Unsafety::Normal, hir::ImplPolarity::Negative(_))
59 | (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive)
60 | (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive)
61 | (Unsafety::Normal, None, Unsafety::Normal, _) => {