Add warn(unreachable_pub) to rustc_privacy.

compiler/rustc_privacy/src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(let_chains)]
 #![feature(rustdoc_internals)]
 #![feature(try_blocks)]
+#![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
 mod errors;
@@ -1497,7 +1498,7 @@ impl<'tcx> PrivateItemsInPublicInterfacesChecker<'tcx, '_> {
         self.effective_visibilities.effective_vis(def_id).copied()
     }
 
-    pub fn check_item(&mut self, id: ItemId) {
+    fn check_item(&mut self, id: ItemId) {
         let tcx = self.tcx;
         let def_id = id.owner_id.def_id;
         let item_visibility = tcx.local_visibility(def_id);