src/librustc_typeck/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::ty::TyCtxt;
   5 use rustc_errors::struct_span_err;
   6 use rustc_hir as hir;
   7 use rustc_hir::itemlikevisit::ItemLikeVisitor;
   8 use rustc_hir::Unsafety;
   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         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")
  32             });
  33             match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
  34                 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
  35                     struct_span_err!(
  36                         self.tcx.sess,
  37                         item.span,
  38                         E0199,
  39                         "implementing the trait `{}` is not unsafe",
  40                         trait_ref.print_only_trait_path()
  41                     )
  42                     .emit();
  43                 }
  44
  45                 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  46                     struct_span_err!(
  47                         self.tcx.sess,
  48                         item.span,
  49                         E0200,
  50                         "the trait `{}` requires an `unsafe impl` declaration",
  51                         trait_ref.print_only_trait_path()
  52                     )
  53                     .emit();
  54                 }
  55
  56                 (
  57                     Unsafety::Normal,
  58                     Some(attr_name),
  59                     Unsafety::Normal,
  60                     hir::ImplPolarity::Positive,
  61                 ) => {
  62                     struct_span_err!(
  63                         self.tcx.sess,
  64                         item.span,
  65                         E0569,
  66                         "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  67                         attr_name
  68                     )
  69                     .emit();
  70                 }
  71
  72                 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative) => {
  73                     // Reported in AST validation
  74                     self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  75                 }
  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, _) => {
  80                     // OK
  81                 }
  82             }
  83         }
  84     }
  85 }
  86
  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);
  91         }
  92     }
  93
  94     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
  95
  96     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
  97 }