src/librustc_typeck/coherence/inherent_impls_overlap.rs

   1 use rustc::ty::TyCtxt;
   2 use rustc_errors::struct_span_err;
   3 use rustc_hir as hir;
   4 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
   5 use rustc_hir::itemlikevisit::ItemLikeVisitor;
   6 use rustc_infer::traits::{self, SkipLeakCheck};
   7
   8 pub fn crate_inherent_impls_overlap_check(tcx: TyCtxt<'_>, crate_num: CrateNum) {
   9     assert_eq!(crate_num, LOCAL_CRATE);
  10     let krate = tcx.hir().krate();
  11     krate.visit_all_item_likes(&mut InherentOverlapChecker { tcx });
  12 }
  13
  14 struct InherentOverlapChecker<'tcx> {
  15     tcx: TyCtxt<'tcx>,
  16 }
  17
  18 impl InherentOverlapChecker<'tcx> {
  19     /// Checks whether any associated items in impls 1 and 2 share the same identifier and
  20     /// namespace.
  21     fn impls_have_common_items(&self, impl1: DefId, impl2: DefId) -> bool {
  22         let impl_items1 = self.tcx.associated_items(impl1);
  23         let impl_items2 = self.tcx.associated_items(impl2);
  24
  25         for item1 in impl_items1.in_definition_order() {
  26             let collision = impl_items2.filter_by_name_unhygienic(item1.ident.name).any(|item2| {
  27                 // Symbols and namespace match, compare hygienically.
  28                 item1.kind.namespace() == item2.kind.namespace()
  29                     && item1.ident.modern() == item2.ident.modern()
  30             });
  31
  32             if collision {
  33                 return true;
  34             }
  35         }
  36
  37         false
  38     }
  39
  40     fn check_for_common_items_in_impls(
  41         &self,
  42         impl1: DefId,
  43         impl2: DefId,
  44         overlap: traits::OverlapResult<'_>,
  45     ) {
  46         let impl_items1 = self.tcx.associated_items(impl1);
  47         let impl_items2 = self.tcx.associated_items(impl2);
  48
  49         for item1 in impl_items1.in_definition_order() {
  50             let collision = impl_items2.filter_by_name_unhygienic(item1.ident.name).find(|item2| {
  51                 // Symbols and namespace match, compare hygienically.
  52                 item1.kind.namespace() == item2.kind.namespace()
  53                     && item1.ident.modern() == item2.ident.modern()
  54             });
  55
  56             if let Some(item2) = collision {
  57                 let name = item1.ident.modern();
  58                 let mut err = struct_span_err!(
  59                     self.tcx.sess,
  60                     self.tcx.span_of_impl(item1.def_id).unwrap(),
  61                     E0592,
  62                     "duplicate definitions with name `{}`",
  63                     name
  64                 );
  65                 err.span_label(
  66                     self.tcx.span_of_impl(item1.def_id).unwrap(),
  67                     format!("duplicate definitions for `{}`", name),
  68                 );
  69                 err.span_label(
  70                     self.tcx.span_of_impl(item2.def_id).unwrap(),
  71                     format!("other definition for `{}`", name),
  72                 );
  73
  74                 for cause in &overlap.intercrate_ambiguity_causes {
  75                     cause.add_intercrate_ambiguity_hint(&mut err);
  76                 }
  77
  78                 if overlap.involves_placeholder {
  79                     traits::add_placeholder_note(&mut err);
  80                 }
  81
  82                 err.emit();
  83             }
  84         }
  85     }
  86
  87     fn check_for_overlapping_inherent_impls(&self, impl1_def_id: DefId, impl2_def_id: DefId) {
  88         traits::overlapping_impls(
  89             self.tcx,
  90             impl1_def_id,
  91             impl2_def_id,
  92             // We go ahead and just skip the leak check for
  93             // inherent impls without warning.
  94             SkipLeakCheck::Yes,
  95             |overlap| {
  96                 self.check_for_common_items_in_impls(impl1_def_id, impl2_def_id, overlap);
  97                 false
  98             },
  99             || true,
 100         );
 101     }
 102 }
 103
 104 impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
 105     fn visit_item(&mut self, item: &'v hir::Item<'v>) {
 106         match item.kind {
 107             hir::ItemKind::Enum(..)
 108             | hir::ItemKind::Struct(..)
 109             | hir::ItemKind::Trait(..)
 110             | hir::ItemKind::Union(..) => {
 111                 let ty_def_id = self.tcx.hir().local_def_id(item.hir_id);
 112                 let impls = self.tcx.inherent_impls(ty_def_id);
 113
 114                 for (i, &impl1_def_id) in impls.iter().enumerate() {
 115                     for &impl2_def_id in &impls[(i + 1)..] {
 116                         if self.impls_have_common_items(impl1_def_id, impl2_def_id) {
 117                             self.check_for_overlapping_inherent_impls(impl1_def_id, impl2_def_id);
 118                         }
 119                     }
 120                 }
 121             }
 122             _ => {}
 123         }
 124     }
 125
 126     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'v>) {}
 127
 128     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'v>) {}
 129 }