src/librustc_passes/diagnostic_items.rs

   1 //! Detecting diagnostic items.
   2 //!
   3 //! Diagnostic items are items that are not language-inherent, but can reasonably be expected to
   4 //! exist for diagnostic purposes. This allows diagnostic authors to refer to specific items
   5 //! directly, without having to guess module paths and crates.
   6 //! Examples are:
   7 //!
   8 //! * Traits like `Debug`, that have no bearing on language semantics
   9 //!
  10 //! * Compiler internal types like `Ty` and `TyCtxt`
  11
  12 use rustc_ast as ast;
  13 use rustc_data_structures::fx::FxHashMap;
  14 use rustc_hir as hir;
  15 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
  16 use rustc_hir::itemlikevisit::ItemLikeVisitor;
  17 use rustc_middle::ty::query::Providers;
  18 use rustc_middle::ty::TyCtxt;
  19 use rustc_session::Session;
  20 use rustc_span::symbol::{sym, Symbol};
  21
  22 struct DiagnosticItemCollector<'tcx> {
  23     // items from this crate
  24     items: FxHashMap<Symbol, DefId>,
  25     tcx: TyCtxt<'tcx>,
  26 }
  27
  28 impl<'v, 'tcx> ItemLikeVisitor<'v> for DiagnosticItemCollector<'tcx> {
  29     fn visit_item(&mut self, item: &hir::Item<'_>) {
  30         self.observe_item(&item.attrs, item.hir_id);
  31     }
  32
  33     fn visit_trait_item(&mut self, trait_item: &hir::TraitItem<'_>) {
  34         self.observe_item(&trait_item.attrs, trait_item.hir_id);
  35     }
  36
  37     fn visit_impl_item(&mut self, impl_item: &hir::ImplItem<'_>) {
  38         self.observe_item(&impl_item.attrs, impl_item.hir_id);
  39     }
  40 }
  41
  42 impl<'tcx> DiagnosticItemCollector<'tcx> {
  43     fn new(tcx: TyCtxt<'tcx>) -> DiagnosticItemCollector<'tcx> {
  44         DiagnosticItemCollector { tcx, items: Default::default() }
  45     }
  46
  47     fn observe_item(&mut self, attrs: &[ast::Attribute], hir_id: hir::HirId) {
  48         if let Some(name) = extract(&self.tcx.sess, attrs) {
  49             let def_id = self.tcx.hir().local_def_id(hir_id);
  50             // insert into our table
  51             collect_item(self.tcx, &mut self.items, name, def_id.to_def_id());
  52         }
  53     }
  54 }
  55
  56 fn collect_item(
  57     tcx: TyCtxt<'_>,
  58     items: &mut FxHashMap<Symbol, DefId>,
  59     name: Symbol,
  60     item_def_id: DefId,
  61 ) {
  62     // Check for duplicates.
  63     if let Some(original_def_id) = items.insert(name, item_def_id) {
  64         if original_def_id != item_def_id {
  65             let mut err = match tcx.hir().span_if_local(item_def_id) {
  66                 Some(span) => tcx.sess.struct_span_err(
  67                     span,
  68                     &format!("duplicate diagnostic item found: `{}`.", name),
  69                 ),
  70                 None => tcx.sess.struct_err(&format!(
  71                     "duplicate diagnostic item in crate `{}`: `{}`.",
  72                     tcx.crate_name(item_def_id.krate),
  73                     name
  74                 )),
  75             };
  76             if let Some(span) = tcx.hir().span_if_local(original_def_id) {
  77                 err.span_note(span, "the diagnostic item is first defined here");
  78             } else {
  79                 err.note(&format!(
  80                     "the diagnostic item is first defined in crate `{}`.",
  81                     tcx.crate_name(original_def_id.krate)
  82                 ));
  83             }
  84             err.emit();
  85         }
  86     }
  87 }
  88
  89 /// Extract the first `rustc_diagnostic_item = "$name"` out of a list of attributes.
  90 fn extract(sess: &Session, attrs: &[ast::Attribute]) -> Option<Symbol> {
  91     attrs.iter().find_map(|attr| {
  92         if sess.check_name(attr, sym::rustc_diagnostic_item) { attr.value_str() } else { None }
  93     })
  94 }
  95
  96 /// Traverse and collect the diagnostic items in the current
  97 fn collect<'tcx>(tcx: TyCtxt<'tcx>) -> FxHashMap<Symbol, DefId> {
  98     // Initialize the collector.
  99     let mut collector = DiagnosticItemCollector::new(tcx);
 100
 101     // Collect diagnostic items in this crate.
 102     tcx.hir().krate().visit_all_item_likes(&mut collector);
 103
 104     collector.items
 105 }
 106
 107 /// Traverse and collect all the diagnostic items in all crates.
 108 fn collect_all<'tcx>(tcx: TyCtxt<'tcx>) -> FxHashMap<Symbol, DefId> {
 109     // Initialize the collector.
 110     let mut collector = FxHashMap::default();
 111
 112     // Collect diagnostic items in other crates.
 113     for &cnum in tcx.crates().iter().chain(std::iter::once(&LOCAL_CRATE)) {
 114         for (&name, &def_id) in tcx.diagnostic_items(cnum).iter() {
 115             collect_item(tcx, &mut collector, name, def_id);
 116         }
 117     }
 118
 119     collector
 120 }
 121
 122 pub fn provide(providers: &mut Providers) {
 123     providers.diagnostic_items = |tcx, id| {
 124         assert_eq!(id, LOCAL_CRATE);
 125         collect(tcx)
 126     };
 127     providers.all_diagnostic_items = |tcx, id| {
 128         assert_eq!(id, LOCAL_CRATE);
 129         collect_all(tcx)
 130     };
 131 }