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 use rustc_error_codes::*;
  11
  12 pub fn check(tcx: TyCtxt<'_>) {
  13     let mut unsafety = UnsafetyChecker { tcx };
  14     tcx.hir().krate().visit_all_item_likes(&mut unsafety);
  15 }
  16
  17 struct UnsafetyChecker<'tcx> {
  18     tcx: TyCtxt<'tcx>,
  19 }
  20
  21 impl UnsafetyChecker<'tcx> {
  22     fn check_unsafety_coherence(
  23         &mut self,
  24         item: &'v hir::Item<'v>,
  25         impl_generics: Option<&hir::Generics<'_>>,
  26         unsafety: hir::Unsafety,
  27         polarity: hir::ImplPolarity,
  28     ) {
  29         let local_did = self.tcx.hir().local_def_id(item.hir_id);
  30         if let Some(trait_ref) = self.tcx.impl_trait_ref(local_did) {
  31             let trait_def = self.tcx.trait_def(trait_ref.def_id);
  32             let unsafe_attr = impl_generics.and_then(|generics| {
  33                 generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle")
  34             });
  35             match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
  36                 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
  37                     struct_span_err!(
  38                         self.tcx.sess,
  39                         item.span,
  40                         E0199,
  41                         "implementing the trait `{}` is not unsafe",
  42                         trait_ref.print_only_trait_path()
  43                     )
  44                     .emit();
  45                 }
  46
  47                 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  48                     struct_span_err!(
  49                         self.tcx.sess,
  50                         item.span,
  51                         E0200,
  52                         "the trait `{}` requires an `unsafe impl` declaration",
  53                         trait_ref.print_only_trait_path()
  54                     )
  55                     .emit();
  56                 }
  57
  58                 (
  59                     Unsafety::Normal,
  60                     Some(attr_name),
  61                     Unsafety::Normal,
  62                     hir::ImplPolarity::Positive,
  63                 ) => {
  64                     struct_span_err!(
  65                         self.tcx.sess,
  66                         item.span,
  67                         E0569,
  68                         "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  69                         attr_name
  70                     )
  71                     .emit();
  72                 }
  73
  74                 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative) => {
  75                     // Reported in AST validation
  76                     self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  77                 }
  78                 (_, _, Unsafety::Normal, hir::ImplPolarity::Negative)
  79                 | (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive)
  80                 | (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive)
  81                 | (Unsafety::Normal, None, Unsafety::Normal, _) => {
  82                     // OK
  83                 }
  84             }
  85         }
  86     }
  87 }
  88
  89 impl ItemLikeVisitor<'v> for UnsafetyChecker<'tcx> {
  90     fn visit_item(&mut self, item: &'v hir::Item<'v>) {
  91         if let hir::ItemKind::Impl { unsafety, polarity, ref generics, .. } = item.kind {
  92             self.check_unsafety_coherence(item, Some(generics), unsafety, polarity);
  93         }
  94     }
  95
  96     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'_>) {}
  97
  98     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'_>) {}
  99 }