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
  27                 .filter_by_name_unhygienic(item1.ident.name)
  28                 .find(|item2| {
  29                     // Symbols and namespace match, compare hygienically.
  30                     item1.kind.namespace() == item2.kind.namespace()
  31                         && item1.ident.modern() == item2.ident.modern()
  32                 })
  33                 .is_some();
  34
  35             if collision {
  36                 return true;
  37             }
  38         }
  39
  40         false
  41     }
  42
  43     fn check_for_common_items_in_impls(
  44         &self,
  45         impl1: DefId,
  46         impl2: DefId,
  47         overlap: traits::OverlapResult<'_>,
  48     ) {
  49         let impl_items1 = self.tcx.associated_items(impl1);
  50         let impl_items2 = self.tcx.associated_items(impl2);
  51
  52         for item1 in impl_items1.in_definition_order() {
  53             let collision = impl_items2.filter_by_name_unhygienic(item1.ident.name).find(|item2| {
  54                 // Symbols and namespace match, compare hygienically.
  55                 item1.kind.namespace() == item2.kind.namespace()
  56                     && item1.ident.modern() == item2.ident.modern()
  57             });
  58
  59             if let Some(item2) = collision {
  60                 let name = item1.ident.modern();
  61                 let mut err = struct_span_err!(
  62                     self.tcx.sess,
  63                     self.tcx.span_of_impl(item1.def_id).unwrap(),
  64                     E0592,
  65                     "duplicate definitions with name `{}`",
  66                     name
  67                 );
  68                 err.span_label(
  69                     self.tcx.span_of_impl(item1.def_id).unwrap(),
  70                     format!("duplicate definitions for `{}`", name),
  71                 );
  72                 err.span_label(
  73                     self.tcx.span_of_impl(item2.def_id).unwrap(),
  74                     format!("other definition for `{}`", name),
  75                 );
  76
  77                 for cause in &overlap.intercrate_ambiguity_causes {
  78                     cause.add_intercrate_ambiguity_hint(&mut err);
  79                 }
  80
  81                 if overlap.involves_placeholder {
  82                     traits::add_placeholder_note(&mut err);
  83                 }
  84
  85                 err.emit();
  86             }
  87         }
  88     }
  89
  90     fn check_for_overlapping_inherent_impls(&self, impl1_def_id: DefId, impl2_def_id: DefId) {
  91         traits::overlapping_impls(
  92             self.tcx,
  93             impl1_def_id,
  94             impl2_def_id,
  95             // We go ahead and just skip the leak check for
  96             // inherent impls without warning.
  97             SkipLeakCheck::Yes,
  98             |overlap| {
  99                 self.check_for_common_items_in_impls(impl1_def_id, impl2_def_id, overlap);
 100                 false
 101             },
 102             || true,
 103         );
 104     }
 105 }
 106
 107 impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
 108     fn visit_item(&mut self, item: &'v hir::Item<'v>) {
 109         match item.kind {
 110             hir::ItemKind::Enum(..)
 111             | hir::ItemKind::Struct(..)
 112             | hir::ItemKind::Trait(..)
 113             | hir::ItemKind::Union(..) => {
 114                 let ty_def_id = self.tcx.hir().local_def_id(item.hir_id);
 115                 let impls = self.tcx.inherent_impls(ty_def_id);
 116
 117                 for (i, &impl1_def_id) in impls.iter().enumerate() {
 118                     for &impl2_def_id in &impls[(i + 1)..] {
 119                         if self.impls_have_common_items(impl1_def_id, impl2_def_id) {
 120                             self.check_for_overlapping_inherent_impls(impl1_def_id, impl2_def_id);
 121                         }
 122                     }
 123                 }
 124             }
 125             _ => {}
 126         }
 127     }
 128
 129     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem<'v>) {}
 130
 131     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem<'v>) {}
 132 }