compiler/rustc_typeck/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
  10 pub fn check(tcx: TyCtxt<'_>) {
  11     for id in tcx.hir().items() {
  12         if matches!(tcx.def_kind(id.def_id), DefKind::Impl) {
  13             let item = tcx.hir().item(id);
  14             if let hir::ItemKind::Impl(ref impl_) = item.kind {
  15                 check_unsafety_coherence(
  16                     tcx,
  17                     item,
  18                     Some(&impl_.generics),
  19                     impl_.unsafety,
  20                     impl_.polarity,
  21                 );
  22             }
  23         }
  24     }
  25 }
  26
  27 fn check_unsafety_coherence<'tcx>(
  28     tcx: TyCtxt<'tcx>,
  29     item: &hir::Item<'_>,
  30     impl_generics: Option<&hir::Generics<'_>>,
  31     unsafety: hir::Unsafety,
  32     polarity: hir::ImplPolarity,
  33 ) {
  34     if let Some(trait_ref) = tcx.impl_trait_ref(item.def_id) {
  35         let trait_def = tcx.trait_def(trait_ref.def_id);
  36         let unsafe_attr = impl_generics.and_then(|generics| {
  37             generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle")
  38         });
  39         match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
  40             (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
  41                 struct_span_err!(
  42                     tcx.sess,
  43                     item.span,
  44                     E0199,
  45                     "implementing the trait `{}` is not unsafe",
  46                     trait_ref.print_only_trait_path()
  47                 )
  48                 .emit();
  49             }
  50
  51             (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  52                 struct_span_err!(
  53                     tcx.sess,
  54                     item.span,
  55                     E0200,
  56                     "the trait `{}` requires an `unsafe impl` declaration",
  57                     trait_ref.print_only_trait_path()
  58                 )
  59                 .emit();
  60             }
  61
  62             (Unsafety::Normal, Some(attr_name), Unsafety::Normal, hir::ImplPolarity::Positive) => {
  63                 struct_span_err!(
  64                     tcx.sess,
  65                     item.span,
  66                     E0569,
  67                     "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  68                     attr_name
  69                 )
  70                 .emit();
  71             }
  72
  73             (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative(_)) => {
  74                 // Reported in AST validation
  75                 tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  76             }
  77             (_, _, Unsafety::Normal, hir::ImplPolarity::Negative(_))
  78             | (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive)
  79             | (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive)
  80             | (Unsafety::Normal, None, Unsafety::Normal, _) => {
  81                 // OK
  82             }
  83         }
  84     }
  85 }