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::itemlikevisit::ItemLikeVisitor;
   7 use rustc_hir::Unsafety;
   8 use rustc_middle::ty::TyCtxt;
   9
  10 pub fn check(tcx: TyCtxt<'_>) {
  11     let mut unsafety = UnsafetyChecker { tcx };
  12     tcx.hir().krate().visit_all_item_likes(&mut unsafety);
  13 }
  14
  15 struct UnsafetyChecker<'tcx> {
  16     tcx: TyCtxt<'tcx>,
  17 }
  18
  19 impl UnsafetyChecker<'tcx> {
  20     fn check_unsafety_coherence(
  21         &mut self,
  22         item: &'v hir::Item<'v>,
  23         impl_generics: Option<&hir::Generics<'_>>,
  24         unsafety: hir::Unsafety,
  25         polarity: hir::ImplPolarity,
  26     ) {
  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")
  31             });
  32             match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
  33                 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
  34                     struct_span_err!(
  35                         self.tcx.sess,
  36                         item.span,
  37                         E0199,
  38                         "implementing the trait `{}` is not unsafe",
  39                         trait_ref.print_only_trait_path()
  40                     )
  41                     .emit();
  42                 }
  43
  44                 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  45                     struct_span_err!(
  46                         self.tcx.sess,
  47                         item.span,
  48                         E0200,
  49                         "the trait `{}` requires an `unsafe impl` declaration",
  50                         trait_ref.print_only_trait_path()
  51                     )
  52                     .emit();
  53                 }
  54
  55                 (
  56                     Unsafety::Normal,
  57                     Some(attr_name),
  58                     Unsafety::Normal,
  59                     hir::ImplPolarity::Positive,
  60                 ) => {
  61                     struct_span_err!(
  62                         self.tcx.sess,
  63                         item.span,
  64                         E0569,
  65                         "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  66                         attr_name
  67                     )
  68                     .emit();
  69                 }
  70
  71                 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative(_)) => {
  72                     // Reported in AST validation
  73                     self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  74                 }
  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, _) => {
  79                     // OK
  80                 }
  81             }
  82         }
  83     }
  84 }
  85
  86 impl ItemLikeVisitor<'v> for UnsafetyChecker<'tcx> {
  87     fn visit_item(&mut self, item: &'v hir::Item<'v>) {
  88         if let hir::ItemKind::Impl(ref impl_) = item.kind {
  89             self.check_unsafety_coherence(
  90                 item,
  91                 Some(&impl_.generics),
  92                 impl_.unsafety,
  93                 impl_.polarity,
  94             );
  95         }
  96     }
  97
  98     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
  99
 100     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
 101
 102     fn visit_foreign_item(&mut self, _foreign_item: &hir::ForeignItem<'_>) {}
 103 }