src/librustc_typeck/coherence/orphan.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 //! Orphan 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::traits;
  15 use middle::ty;
  16 use syntax::ast::{Item, ItemImpl};
  17 use syntax::ast;
  18 use syntax::ast_util;
  19 use syntax::codemap::Span;
  20 use syntax::visit;
  21 use util::ppaux::{Repr, UserString};
  22
  23 pub fn check(tcx: &ty::ctxt) {
  24     let mut orphan = OrphanChecker { tcx: tcx };
  25     visit::walk_crate(&mut orphan, tcx.map.krate());
  26 }
  27
  28 struct OrphanChecker<'cx, 'tcx:'cx> {
  29     tcx: &'cx ty::ctxt<'tcx>
  30 }
  31
  32 impl<'cx, 'tcx> OrphanChecker<'cx, 'tcx> {
  33     fn check_def_id(&self, span: Span, def_id: ast::DefId) {
  34         if def_id.krate != ast::LOCAL_CRATE {
  35             span_err!(self.tcx.sess, span, E0116,
  36                       "cannot associate methods with a type outside the \
  37                        crate the type is defined in; define and implement \
  38                        a trait or new type instead");
  39         }
  40     }
  41 }
  42
  43 impl<'cx, 'tcx,'v> visit::Visitor<'v> for OrphanChecker<'cx, 'tcx> {
  44     fn visit_item(&mut self, item: &'v ast::Item) {
  45         let def_id = ast_util::local_def(item.id);
  46         match item.node {
  47             ast::ItemImpl(_, _, _, None, _, _) => {
  48                 // For inherent impls, self type must be a nominal type
  49                 // defined in this crate.
  50                 debug!("coherence2::orphan check: inherent impl {}", item.repr(self.tcx));
  51                 let self_ty = ty::lookup_item_type(self.tcx, def_id).ty;
  52                 match self_ty.sty {
  53                     ty::ty_enum(def_id, _) |
  54                     ty::ty_struct(def_id, _) => {
  55                         self.check_def_id(item.span, def_id);
  56                     }
  57                     ty::ty_trait(ref data) => {
  58                         self.check_def_id(item.span, data.principal_def_id());
  59                     }
  60                     ty::ty_uniq(..) => {
  61                         self.check_def_id(item.span,
  62                                           self.tcx.lang_items.owned_box()
  63                                               .unwrap());
  64                     }
  65                     _ => {
  66                         span_err!(self.tcx.sess, item.span, E0118,
  67                                   "no base type found for inherent implementation; \
  68                                    implement a trait or new type instead");
  69                     }
  70                 }
  71             }
  72             ast::ItemImpl(_, _, _, Some(_), _, _) => {
  73                 // "Trait" impl
  74                 debug!("coherence2::orphan check: trait impl {}", item.repr(self.tcx));
  75                 let trait_def_id = ty::impl_trait_ref(self.tcx, def_id).unwrap().def_id;
  76                 match traits::orphan_check(self.tcx, def_id) {
  77                     Ok(()) => { }
  78                     Err(traits::OrphanCheckErr::NoLocalInputType) => {
  79                         if !ty::has_attr(self.tcx, trait_def_id, "old_orphan_check") {
  80                             let self_ty = ty::lookup_item_type(self.tcx, def_id).ty;
  81                             span_err!(
  82                                 self.tcx.sess, item.span, E0117,
  83                                 "the type `{}` does not reference any \
  84                                  types defined in this crate; \
  85                                  only traits defined in the current crate can be \
  86                                  implemented for arbitrary types",
  87                                 self_ty.user_string(self.tcx));
  88                         }
  89                     }
  90                     Err(traits::OrphanCheckErr::UncoveredTy(param_ty)) => {
  91                         if !ty::has_attr(self.tcx, trait_def_id, "old_orphan_check") {
  92                             self.tcx.sess.span_err(
  93                                 item.span,
  94                                 format!(
  95                                     "type parameter `{}` is not constrained by any local type; \
  96                                      only traits defined in the current crate can be implemented \
  97                                      for a type parameter",
  98                                     param_ty.user_string(self.tcx)).as_slice());
  99                             self.tcx.sess.span_note(
 100                                 item.span,
 101                                 format!("for a limited time, you can add \
 102                                          `#![feature(old_orphan_check)]` to your crate \
 103                                          to disable this rule").as_slice());
 104                         }
 105                     }
 106                 }
 107             }
 108             _ => {
 109                 // Not an impl
 110             }
 111         }
 112
 113         visit::walk_item(self, item);
 114     }
 115 }