compiler/rustc_hir_analysis/src/coherence/unsafety.rs

   1 //! Unsafety checker: every impl either implements a trait defined in this
   2 //! crate or pertains to a type defined in this crate.
   3
   4 use rustc_errors::struct_span_err;
   5 use rustc_hir as hir;
   6 use rustc_hir::def::DefKind;
   7 use rustc_hir::Unsafety;
   8 use rustc_middle::ty::TyCtxt;
   9 use rustc_span::def_id::LocalDefId;
  10
  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!() };
  15
  16     if let Some(trait_ref) = tcx.impl_trait_ref(item.def_id) {
  17         let trait_def = tcx.trait_def(trait_ref.def_id);
  18         let unsafe_attr =
  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) => {
  22                 struct_span_err!(
  23                     tcx.sess,
  24                     item.span,
  25                     E0199,
  26                     "implementing the trait `{}` is not unsafe",
  27                     trait_ref.print_only_trait_path()
  28                 )
  29                 .emit();
  30             }
  31
  32             (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  33                 struct_span_err!(
  34                     tcx.sess,
  35                     item.span,
  36                     E0200,
  37                     "the trait `{}` requires an `unsafe impl` declaration",
  38                     trait_ref.print_only_trait_path()
  39                 )
  40                 .emit();
  41             }
  42
  43             (Unsafety::Normal, Some(attr_name), Unsafety::Normal, hir::ImplPolarity::Positive) => {
  44                 struct_span_err!(
  45                     tcx.sess,
  46                     item.span,
  47                     E0569,
  48                     "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  49                     attr_name
  50                 )
  51                 .emit();
  52             }
  53
  54             (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative(_)) => {
  55                 // Reported in AST validation
  56                 tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  57             }
  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, _) => {
  62                 // OK
  63             }
  64         }
  65     }
  66 }