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 use util::ppaux::UserString;
  20
  21 pub fn check(tcx: &ty::ctxt) {
  22     let mut orphan = UnsafetyChecker { tcx: tcx };
  23     visit::walk_crate(&mut orphan, tcx.map.krate());
  24 }
  25
  26 struct UnsafetyChecker<'cx, 'tcx:'cx> {
  27     tcx: &'cx ty::ctxt<'tcx>
  28 }
  29
  30 impl<'cx, 'tcx,'v> visit::Visitor<'v> for UnsafetyChecker<'cx, 'tcx> {
  31     fn visit_item(&mut self, item: &'v ast::Item) {
  32         match item.node {
  33             ast::ItemImpl(unsafety, polarity, _, _, _, _) => {
  34                 match ty::impl_trait_ref(self.tcx, ast_util::local_def(item.id)) {
  35                     None => {
  36                         // Inherent impl.
  37                         match unsafety {
  38                             ast::Unsafety::Normal => { /* OK */ }
  39                             ast::Unsafety::Unsafe => {
  40                                 self.tcx.sess.span_err(
  41                                     item.span,
  42                                     "inherent impls cannot be declared as unsafe");
  43                             }
  44                         }
  45                     }
  46
  47                     Some(trait_ref) => {
  48                         let trait_def = ty::lookup_trait_def(self.tcx, trait_ref.def_id);
  49                         match (trait_def.unsafety, unsafety, polarity) {
  50                             (ast::Unsafety::Unsafe,
  51                              ast::Unsafety::Unsafe, ast::ImplPolarity::Negative) => {
  52                                 self.tcx.sess.span_err(
  53                                     item.span,
  54                                     format!("negative implementations are not unsafe").as_slice());
  55                             }
  56
  57                             (ast::Unsafety::Normal, ast::Unsafety::Unsafe, _) => {
  58                                 self.tcx.sess.span_err(
  59                                     item.span,
  60                                     format!("implementing the trait `{}` is not unsafe",
  61                                             trait_ref.user_string(self.tcx)).as_slice());
  62                             }
  63
  64                             (ast::Unsafety::Unsafe,
  65                              ast::Unsafety::Normal, ast::ImplPolarity::Positive) => {
  66                                 self.tcx.sess.span_err(
  67                                     item.span,
  68                                     format!("the trait `{}` requires an `unsafe impl` declaration",
  69                                             trait_ref.user_string(self.tcx)).as_slice());
  70                             }
  71
  72                             (ast::Unsafety::Unsafe,
  73                              ast::Unsafety::Normal, ast::ImplPolarity::Negative) |
  74                             (ast::Unsafety::Unsafe,
  75                              ast::Unsafety::Unsafe, ast::ImplPolarity::Positive) |
  76                             (ast::Unsafety::Normal, ast::Unsafety::Normal, _) => {
  77                                 /* OK */
  78                             }
  79                         }
  80                     }
  81                 }
  82             }
  83             _ => { }
  84         }
  85
  86         visit::walk_item(self, item);
  87     }
  88 }