src/librustc_typeck/coherence/unsafety.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Unsafety checker: every impl either implements a trait defined in this
  12 //! crate or pertains to a type defined in this crate.
  13
  14 use middle::ty;
  15 use syntax::ast::{Item, ItemImpl};
  16 use syntax::ast;
  17 use syntax::ast_util;
  18 use syntax::visit;
  19
  20 pub fn check(tcx: &ty::ctxt) {
  21     let mut orphan = UnsafetyChecker { tcx: tcx };
  22     visit::walk_crate(&mut orphan, tcx.map.krate());
  23 }
  24
  25 struct UnsafetyChecker<'cx, 'tcx:'cx> {
  26     tcx: &'cx ty::ctxt<'tcx>
  27 }
  28
  29 impl<'cx, 'tcx, 'v> UnsafetyChecker<'cx, 'tcx> {
  30     fn check_unsafety_coherence(&mut self, item: &'v ast::Item,
  31                                 unsafety: ast::Unsafety,
  32                                 polarity: ast::ImplPolarity) {
  33         match self.tcx.impl_trait_ref(ast_util::local_def(item.id)) {
  34             None => {
  35                 // Inherent impl.
  36                 match unsafety {
  37                     ast::Unsafety::Normal => { /* OK */ }
  38                     ast::Unsafety::Unsafe => {
  39                         span_err!(self.tcx.sess, item.span, E0197,
  40                                   "inherent impls cannot be declared as unsafe");
  41                     }
  42                 }
  43             }
  44
  45             Some(trait_ref) => {
  46                 let trait_def = self.tcx.lookup_trait_def(trait_ref.def_id);
  47                 match (trait_def.unsafety, unsafety, polarity) {
  48                     (ast::Unsafety::Unsafe,
  49                      ast::Unsafety::Unsafe, ast::ImplPolarity::Negative) => {
  50                         span_err!(self.tcx.sess, item.span, E0198,
  51                                   "negative implementations are not unsafe");
  52                     }
  53
  54                     (ast::Unsafety::Normal, ast::Unsafety::Unsafe, _) => {
  55                         span_err!(self.tcx.sess, item.span, E0199,
  56                                   "implementing the trait `{}` is not unsafe",
  57                                   trait_ref);
  58                     }
  59
  60                     (ast::Unsafety::Unsafe,
  61                      ast::Unsafety::Normal, ast::ImplPolarity::Positive) => {
  62                         span_err!(self.tcx.sess, item.span, E0200,
  63                                   "the trait `{}` requires an `unsafe impl` declaration",
  64                                   trait_ref);
  65                     }
  66
  67                     (ast::Unsafety::Unsafe,
  68                      ast::Unsafety::Normal, ast::ImplPolarity::Negative) |
  69                     (ast::Unsafety::Unsafe,
  70                      ast::Unsafety::Unsafe, ast::ImplPolarity::Positive) |
  71                     (ast::Unsafety::Normal, ast::Unsafety::Normal, _) => {
  72                         /* OK */
  73                     }
  74                 }
  75             }
  76         }
  77     }
  78 }
  79
  80 impl<'cx, 'tcx,'v> visit::Visitor<'v> for UnsafetyChecker<'cx, 'tcx> {
  81     fn visit_item(&mut self, item: &'v ast::Item) {
  82         match item.node {
  83             ast::ItemDefaultImpl(unsafety, _) => {
  84                 self.check_unsafety_coherence(item, unsafety, ast::ImplPolarity::Positive);
  85             }
  86             ast::ItemImpl(unsafety, polarity, _, _, _, _) => {
  87                 self.check_unsafety_coherence(item, unsafety, polarity);
  88             }
  89             _ => { }
  90         }
  91
  92         visit::walk_item(self, item);
  93     }
  94 }