Introduce a query for HIR spans.

Author: cjgillot

src/librustc_middle/hir/map/mod.rs

@@ -828,7 +828,7 @@ impl<'hir> Map<'hir> {
     }
 
     pub fn span(&self, hir_id: HirId) -> Span {
-        self.tcx.index_hir(LOCAL_CRATE).map[hir_id.owner].spans[hir_id.local_id].unwrap()
+        self.tcx.hir_owner_spans(hir_id.owner)[hir_id.local_id].unwrap()
     }
 
     pub fn span_if_local(&self, id: DefId) -> Option<Span> {

src/librustc_middle/hir/mod.rs

@@ -79,5 +79,6 @@ pub fn provide(providers: &mut Providers<'_>) {
     };
     providers.hir_owner = |tcx, id| tcx.index_hir(LOCAL_CRATE).map[id].signature;
     providers.hir_owner_nodes = |tcx, id| tcx.index_hir(LOCAL_CRATE).map[id].with_bodies.as_deref();
+    providers.hir_owner_spans = |tcx, id| &tcx.index_hir(LOCAL_CRATE).map[id].spans;
     map::provide(providers);
 }

src/librustc_middle/query/mod.rs

@@ -89,6 +89,15 @@ rustc_queries! {
             desc { |tcx| "HIR owner items in `{}`", tcx.def_path_str(key.to_def_id()) }
         }
 
+        // Gives access to the HIR spans inside the HIR owner `key`.
+        //
+        // This can be conveniently accessed by methods on `tcx.hir()`.
+        // Avoid calling this query directly.
+        query hir_owner_spans(key: LocalDefId) -> &'tcx IndexVec<ItemLocalId, Option<Span>> {
+            eval_always
+            desc { |tcx| "HIR owner spans in `{}`", tcx.def_path_str(key.to_def_id()) }
+        }
+
         /// Records the type of every item.
         query type_of(key: DefId) -> Ty<'tcx> {
             desc { |tcx| "computing type of `{}`", tcx.def_path_str(key) }