compiler/rustc_passes/src/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_hir::diagnostic_items::DiagnosticItems;
  14 use rustc_middle::ty::query::Providers;
  15 use rustc_middle::ty::TyCtxt;
  16 use rustc_span::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
  17 use rustc_span::symbol::{sym, Symbol};
  18
  19 fn observe_item<'tcx>(
  20     tcx: TyCtxt<'tcx>,
  21     diagnostic_items: &mut DiagnosticItems,
  22     def_id: LocalDefId,
  23 ) {
  24     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
  25     let attrs = tcx.hir().attrs(hir_id);
  26     if let Some(name) = extract(attrs) {
  27         // insert into our table
  28         collect_item(tcx, diagnostic_items, name, def_id.to_def_id());
  29     }
  30 }
  31
  32 fn collect_item(tcx: TyCtxt<'_>, items: &mut DiagnosticItems, name: Symbol, item_def_id: DefId) {
  33     items.id_to_name.insert(item_def_id, name);
  34     if let Some(original_def_id) = items.name_to_id.insert(name, item_def_id) {
  35         if original_def_id != item_def_id {
  36             let mut err = match tcx.hir().span_if_local(item_def_id) {
  37                 Some(span) => tcx
  38                     .sess
  39                     .struct_span_err(span, &format!("duplicate diagnostic item found: `{name}`.")),
  40                 None => tcx.sess.struct_err(&format!(
  41                     "duplicate diagnostic item in crate `{}`: `{}`.",
  42                     tcx.crate_name(item_def_id.krate),
  43                     name
  44                 )),
  45             };
  46             if let Some(span) = tcx.hir().span_if_local(original_def_id) {
  47                 err.span_note(span, "the diagnostic item is first defined here");
  48             } else {
  49                 err.note(&format!(
  50                     "the diagnostic item is first defined in crate `{}`.",
  51                     tcx.crate_name(original_def_id.krate)
  52                 ));
  53             }
  54             err.emit();
  55         }
  56     }
  57 }
  58
  59 /// Extract the first `rustc_diagnostic_item = "$name"` out of a list of attributes.
  60 fn extract(attrs: &[ast::Attribute]) -> Option<Symbol> {
  61     attrs.iter().find_map(|attr| {
  62         if attr.has_name(sym::rustc_diagnostic_item) { attr.value_str() } else { None }
  63     })
  64 }
  65
  66 /// Traverse and collect the diagnostic items in the current
  67 fn diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> DiagnosticItems {
  68     assert_eq!(cnum, LOCAL_CRATE);
  69
  70     // Initialize the collector.
  71     let mut diagnostic_items = DiagnosticItems::default();
  72
  73     // Collect diagnostic items in this crate.
  74     let crate_items = tcx.hir_crate_items(());
  75
  76     for id in crate_items.items() {
  77         observe_item(tcx, &mut diagnostic_items, id.def_id);
  78     }
  79
  80     for id in crate_items.trait_items() {
  81         observe_item(tcx, &mut diagnostic_items, id.def_id);
  82     }
  83
  84     for id in crate_items.impl_items() {
  85         observe_item(tcx, &mut diagnostic_items, id.def_id);
  86     }
  87
  88     for id in crate_items.foreign_items() {
  89         observe_item(tcx, &mut diagnostic_items, id.def_id);
  90     }
  91
  92     diagnostic_items
  93 }
  94
  95 /// Traverse and collect all the diagnostic items in all crates.
  96 fn all_diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, (): ()) -> DiagnosticItems {
  97     // Initialize the collector.
  98     let mut items = DiagnosticItems::default();
  99
 100     // Collect diagnostic items in other crates.
 101     for &cnum in tcx.crates(()).iter().chain(std::iter::once(&LOCAL_CRATE)) {
 102         for (&name, &def_id) in &tcx.diagnostic_items(cnum).name_to_id {
 103             collect_item(tcx, &mut items, name, def_id);
 104         }
 105     }
 106
 107     items
 108 }
 109
 110 pub fn provide(providers: &mut Providers) {
 111     providers.diagnostic_items = diagnostic_items;
 112     providers.all_diagnostic_items = all_diagnostic_items;
 113 }