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::hir::itemlikevisit::ItemLikeVisitor;
   6 use rustc::hir::{self, Unsafety};
   7
   8 pub fn check(tcx: TyCtxt<'_>) {
   9     let mut unsafety = UnsafetyChecker { tcx };
  10     tcx.hir().krate().visit_all_item_likes(&mut unsafety);
  11 }
  12
  13 struct UnsafetyChecker<'tcx> {
  14     tcx: TyCtxt<'tcx>,
  15 }
  16
  17 impl UnsafetyChecker<'tcx> {
  18     fn check_unsafety_coherence(&mut self,
  19                                 item: &'v hir::Item,
  20                                 impl_generics: Option<&hir::Generics>,
  21                                 unsafety: hir::Unsafety,
  22                                 polarity: hir::ImplPolarity)
  23     {
  24         let local_did = self.tcx.hir().local_def_id(item.hir_id);
  25         if let Some(trait_ref) = self.tcx.impl_trait_ref(local_did) {
  26             let trait_def = self.tcx.trait_def(trait_ref.def_id);
  27             let unsafe_attr = impl_generics.and_then(|generics| {
  28                 generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle")
  29             });
  30             match (trait_def.unsafety, unsafe_attr, unsafety, polarity) {
  31                 (Unsafety::Normal, None, Unsafety::Unsafe, hir::ImplPolarity::Positive) => {
  32                     span_err!(self.tcx.sess,
  33                               item.span,
  34                               E0199,
  35                               "implementing the trait `{}` is not unsafe",
  36                               trait_ref);
  37                 }
  38
  39                 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  40                     span_err!(self.tcx.sess,
  41                               item.span,
  42                               E0200,
  43                               "the trait `{}` requires an `unsafe impl` declaration",
  44                               trait_ref);
  45                 }
  46
  47                 (Unsafety::Normal, Some(attr_name), Unsafety::Normal,
  48                     hir::ImplPolarity::Positive) =>
  49                 {
  50                     span_err!(self.tcx.sess,
  51                               item.span,
  52                               E0569,
  53                               "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  54                               attr_name);
  55                 }
  56
  57                 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative) => {
  58                     // Reported in AST validation
  59                     self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  60                 }
  61                 (_, _, Unsafety::Normal, hir::ImplPolarity::Negative) |
  62                 (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive) |
  63                 (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive) |
  64                 (Unsafety::Normal, None, Unsafety::Normal, _) => {
  65                     // OK
  66                 }
  67             }
  68         }
  69     }
  70 }
  71
  72 impl ItemLikeVisitor<'v> for UnsafetyChecker<'tcx> {
  73     fn visit_item(&mut self, item: &'v hir::Item) {
  74         if let hir::ItemKind::Impl(unsafety, polarity, _, ref generics, ..) = item.kind {
  75             self.check_unsafety_coherence(item, Some(generics), unsafety, polarity);
  76         }
  77     }
  78
  79     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
  80     }
  81
  82     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
  83     }
  84 }