Merge the BTreeMap in hir::Crate.

compiler/rustc_middle/src/hir/map/collector.rs

@@ -81,14 +81,10 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             let Crate {
                 ref item,
                 // These fields are handled separately:
-                exported_macros: _,
                 non_exported_macro_attrs: _,
-                items: _,
-                trait_items: _,
-                impl_items: _,
-                foreign_items: _,
-                bodies: _,
+                owners: _,
                 trait_impls: _,
+                bodies: _,
                 body_ids: _,
                 modules: _,
                 proc_macros: _,

compiler/rustc_middle/src/hir/map/mod.rs

@@ -554,8 +554,8 @@ impl<'hir> Map<'hir> {
     where
         V: Visitor<'hir>,
     {
-        for id in self.krate().exported_macros {
-            visitor.visit_macro_def(self.expect_macro_def(id.hir_id()));
+        for macro_def in self.krate().exported_macros() {
+            visitor.visit_macro_def(macro_def);
         }
     }