Introduce get_diagnostic_name

compiler/rustc_hir/src/diagnostic_items.rs

@@ -0,0 +1,17 @@
+use crate::def_id::DefId;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
+use rustc_span::Symbol;
+
+#[derive(Debug, Default)]
+pub struct DiagnosticItems {
+    pub id_to_name: FxHashMap<DefId, Symbol>,
+    pub name_to_id: FxHashMap<Symbol, DefId>,
+}
+
+impl<CTX: crate::HashStableContext> HashStable<CTX> for DiagnosticItems {
+    #[inline]
+    fn hash_stable(&self, ctx: &mut CTX, hasher: &mut StableHasher) {
+        self.name_to_id.hash_stable(ctx, hasher);
+    }
+}

compiler/rustc_hir/src/lib.rs

@@ -18,6 +18,7 @@ mod arena;
 pub mod def;
 pub mod def_path_hash_map;
 pub mod definitions;
+pub mod diagnostic_items;
 pub use rustc_span::def_id;
 mod hir;
 pub mod hir_id;

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -18,6 +18,7 @@ use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIndex, CRATE_DEF_INDEX, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathData, DefPathHash};
+use rustc_hir::diagnostic_items::DiagnosticItems;
 use rustc_hir::lang_items;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::hir::exports::Export;
@@ -1052,16 +1053,23 @@ impl<'a, 'tcx> CrateMetadataRef<'a> {
     }
 
     /// Iterates over the diagnostic items in the given crate.
-    fn get_diagnostic_items(&self) -> FxHashMap<Symbol, DefId> {
+    fn get_diagnostic_items(&self) -> DiagnosticItems {
         if self.root.is_proc_macro_crate() {
             // Proc macro crates do not export any diagnostic-items to the target.
             Default::default()
         } else {
-            self.root
+            let mut id_to_name = FxHashMap::default();
+            let name_to_id = self
+                .root
                 .diagnostic_items
                 .decode(self)
-                .map(|(name, def_index)| (name, self.local_def_id(def_index)))
+                .map(|(name, def_index)| {
-                .collect()
+                    let id = self.local_def_id(def_index);
+                    id_to_name.insert(id, name);
+                    (name, id)
+                })
+                .collect();
+            DiagnosticItems { id_to_name, name_to_id }
         }
     }
 

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1750,7 +1750,7 @@ impl EncodeContext<'a, 'tcx> {
     fn encode_diagnostic_items(&mut self) -> Lazy<[(Symbol, DefIndex)]> {
         empty_proc_macro!(self);
         let tcx = self.tcx;
-        let diagnostic_items = tcx.diagnostic_items(LOCAL_CRATE);
+        let diagnostic_items = &tcx.diagnostic_items(LOCAL_CRATE).name_to_id;
         self.lazy(diagnostic_items.iter().map(|(&name, def_id)| (name, def_id.index)))
     }
 

compiler/rustc_middle/src/query/mod.rs

@@ -1442,7 +1442,7 @@ rustc_queries! {
     }
 
     /// Returns all diagnostic items defined in all crates.
-    query all_diagnostic_items(_: ()) -> FxHashMap<Symbol, DefId> {
+    query all_diagnostic_items(_: ()) -> rustc_hir::diagnostic_items::DiagnosticItems {
         storage(ArenaCacheSelector<'tcx>)
         eval_always
         desc { "calculating the diagnostic items map" }
@@ -1454,7 +1454,7 @@ rustc_queries! {
     }
 
     /// Returns the diagnostic items defined in a crate.
-    query diagnostic_items(_: CrateNum) -> FxHashMap<Symbol, DefId> {
+    query diagnostic_items(_: CrateNum) -> rustc_hir::diagnostic_items::DiagnosticItems {
         storage(ArenaCacheSelector<'tcx>)
         desc { "calculating the diagnostic items map in a crate" }
     }

compiler/rustc_middle/src/ty/context.rs

@@ -1232,12 +1232,17 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Obtain the given diagnostic item's `DefId`. Use `is_diagnostic_item` if you just want to
     /// compare against another `DefId`, since `is_diagnostic_item` is cheaper.
     pub fn get_diagnostic_item(self, name: Symbol) -> Option<DefId> {
-        self.all_diagnostic_items(()).get(&name).copied()
+        self.all_diagnostic_items(()).name_to_id.get(&name).copied()
+    }
+
+    /// Obtain the diagnostic item's name
+    pub fn get_diagnostic_name(self, id: DefId) -> Option<Symbol> {
+        self.diagnostic_items(id.krate).id_to_name.get(&id).copied()
     }
 
     /// Check whether the diagnostic item with the given `name` has the given `DefId`.
     pub fn is_diagnostic_item(self, name: Symbol, did: DefId) -> bool {
-        self.diagnostic_items(did.krate).get(&name) == Some(&did)
+        self.diagnostic_items(did.krate).name_to_id.get(&name) == Some(&did)
     }
 
     pub fn stability(self) -> &'tcx stability::Index<'tcx> {

compiler/rustc_passes/src/diagnostic_items.rs

@@ -10,8 +10,8 @@
 //! * Compiler internal types like `Ty` and `TyCtxt`
 
 use rustc_ast as ast;
-use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
+use rustc_hir::diagnostic_items::DiagnosticItems;
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
@@ -19,9 +19,8 @@ use rustc_span::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use rustc_span::symbol::{sym, Symbol};
 
 struct DiagnosticItemCollector<'tcx> {
-    // items from this crate
-    items: FxHashMap<Symbol, DefId>,
     tcx: TyCtxt<'tcx>,
+    diagnostic_items: DiagnosticItems,
 }
 
 impl<'v, 'tcx> ItemLikeVisitor<'v> for DiagnosticItemCollector<'tcx> {
@@ -44,7 +43,7 @@ impl<'v, 'tcx> ItemLikeVisitor<'v> for DiagnosticItemCollector<'tcx> {
 
 impl<'tcx> DiagnosticItemCollector<'tcx> {
     fn new(tcx: TyCtxt<'tcx>) -> DiagnosticItemCollector<'tcx> {
-        DiagnosticItemCollector { tcx, items: Default::default() }
+        DiagnosticItemCollector { tcx, diagnostic_items: DiagnosticItems::default() }
     }
 
     fn observe_item(&mut self, def_id: LocalDefId) {
@@ -52,19 +51,14 @@ impl<'tcx> DiagnosticItemCollector<'tcx> {
         let attrs = self.tcx.hir().attrs(hir_id);
         if let Some(name) = extract(attrs) {
             // insert into our table
-            collect_item(self.tcx, &mut self.items, name, def_id.to_def_id());
+            collect_item(self.tcx, &mut self.diagnostic_items, name, def_id.to_def_id());
         }
     }
 }
 
-fn collect_item(
+fn collect_item(tcx: TyCtxt<'_>, items: &mut DiagnosticItems, name: Symbol, item_def_id: DefId) {
-    tcx: TyCtxt<'_>,
+    items.id_to_name.insert(item_def_id, name);
-    items: &mut FxHashMap<Symbol, DefId>,
+    if let Some(original_def_id) = items.name_to_id.insert(name, item_def_id) {
-    name: Symbol,
-    item_def_id: DefId,
-) {
-    // Check for duplicates.
-    if let Some(original_def_id) = items.insert(name, item_def_id) {
         if original_def_id != item_def_id {
             let mut err = match tcx.hir().span_if_local(item_def_id) {
                 Some(span) => tcx.sess.struct_span_err(
@@ -98,7 +92,7 @@ fn extract(attrs: &[ast::Attribute]) -> Option<Symbol> {
 }
 
 /// Traverse and collect the diagnostic items in the current
-fn diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> FxHashMap<Symbol, DefId> {
+fn diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> DiagnosticItems {
     assert_eq!(cnum, LOCAL_CRATE);
 
     // Initialize the collector.
@@ -107,22 +101,22 @@ fn diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> FxHashMap<Symbol
     // Collect diagnostic items in this crate.
     tcx.hir().visit_all_item_likes(&mut collector);
 
-    collector.items
+    collector.diagnostic_items
 }
 
 /// Traverse and collect all the diagnostic items in all crates.
-fn all_diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, (): ()) -> FxHashMap<Symbol, DefId> {
+fn all_diagnostic_items<'tcx>(tcx: TyCtxt<'tcx>, (): ()) -> DiagnosticItems {
     // Initialize the collector.
-    let mut collector = FxHashMap::default();
+    let mut items = DiagnosticItems::default();
 
     // Collect diagnostic items in other crates.
     for &cnum in tcx.crates(()).iter().chain(std::iter::once(&LOCAL_CRATE)) {
-        for (&name, &def_id) in tcx.diagnostic_items(cnum).iter() {
+        for (&name, &def_id) in &tcx.diagnostic_items(cnum).name_to_id {
-            collect_item(tcx, &mut collector, name, def_id);
+            collect_item(tcx, &mut items, name, def_id);
         }
     }
 
-    collector
+    items
 }
 
 pub fn provide(providers: &mut Providers) {

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1636,12 +1636,12 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         // Special case the primary error message when send or sync is the trait that was
         // not implemented.
-        let is_send = self.tcx.is_diagnostic_item(sym::Send, trait_ref.def_id);
-        let is_sync = self.tcx.is_diagnostic_item(sym::Sync, trait_ref.def_id);
         let hir = self.tcx.hir();
-        let trait_explanation = if is_send || is_sync {
+        let trait_explanation = if let Some(name @ (sym::Send | sym::Sync)) =
+            self.tcx.get_diagnostic_name(trait_ref.def_id)
+        {
             let (trait_name, trait_verb) =
-                if is_send { ("`Send`", "sent") } else { ("`Sync`", "shared") };
+                if name == sym::Send { ("`Send`", "sent") } else { ("`Sync`", "shared") };
 
             err.clear_code();
             err.set_primary_message(format!(

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -1076,7 +1076,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if adt_def.did.is_local() {
                     let diagnostic_items = self.tcx.diagnostic_items(trait_ref.def_id.krate);
                     return derivables.iter().find_map(|trait_derivable| {
-                        let item_def_id = diagnostic_items.get(trait_derivable)?;
+                        let item_def_id = diagnostic_items.name_to_id.get(trait_derivable)?;
                         if item_def_id == &trait_pred.trait_ref.def_id
                             && !(adt_def.is_enum() && *trait_derivable == sym::Default)
                         {