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 use rustc_error_codes::*;
   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(&mut self,
  21                                 item: &'v hir::Item,
  22                                 impl_generics: Option<&hir::Generics>,
  23                                 unsafety: hir::Unsafety,
  24                                 polarity: hir::ImplPolarity)
  25     {
  26         let local_did = self.tcx.hir().local_def_id(item.hir_id);
  27         if let Some(trait_ref) = self.tcx.impl_trait_ref(local_did) {
  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                     span_err!(self.tcx.sess,
  35                               item.span,
  36                               E0199,
  37                               "implementing the trait `{}` is not unsafe",
  38                               trait_ref.print_only_trait_path());
  39                 }
  40
  41                 (Unsafety::Unsafe, _, Unsafety::Normal, hir::ImplPolarity::Positive) => {
  42                     span_err!(self.tcx.sess,
  43                               item.span,
  44                               E0200,
  45                               "the trait `{}` requires an `unsafe impl` declaration",
  46                               trait_ref.print_only_trait_path());
  47                 }
  48
  49                 (Unsafety::Normal, Some(attr_name), Unsafety::Normal,
  50                     hir::ImplPolarity::Positive) =>
  51                 {
  52                     span_err!(self.tcx.sess,
  53                               item.span,
  54                               E0569,
  55                               "requires an `unsafe impl` declaration due to `#[{}]` attribute",
  56                               attr_name);
  57                 }
  58
  59                 (_, _, Unsafety::Unsafe, hir::ImplPolarity::Negative) => {
  60                     // Reported in AST validation
  61                     self.tcx.sess.delay_span_bug(item.span, "unsafe negative impl");
  62                 }
  63                 (_, _, Unsafety::Normal, hir::ImplPolarity::Negative) |
  64                 (Unsafety::Unsafe, _, Unsafety::Unsafe, hir::ImplPolarity::Positive) |
  65                 (Unsafety::Normal, Some(_), Unsafety::Unsafe, hir::ImplPolarity::Positive) |
  66                 (Unsafety::Normal, None, Unsafety::Normal, _) => {
  67                     // OK
  68                 }
  69             }
  70         }
  71     }
  72 }
  73
  74 impl ItemLikeVisitor<'v> for UnsafetyChecker<'tcx> {
  75     fn visit_item(&mut self, item: &'v hir::Item) {
  76         if let hir::ItemKind::Impl(unsafety, polarity, _, ref generics, ..) = item.kind {
  77             self.check_unsafety_coherence(item, Some(generics), unsafety, polarity);
  78         }
  79     }
  80
  81     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
  82     }
  83
  84     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
  85     }
  86 }