rustc: Parameterize ty::Visibility over used ID

It allows using `LocalDefId` instead of `DefId` when possible, and also encode cheaper `Visibility<DefIndex>` into metadata.

compiler/rustc_resolve/src/lib.rs

@@ -648,7 +648,7 @@ pub struct NameBinding<'a> {
     ambiguity: Option<(&'a NameBinding<'a>, AmbiguityKind)>,
     expansion: LocalExpnId,
     span: Span,
-    vis: ty::Visibility,
+    vis: ty::Visibility<DefId>,
 }
 
 pub trait ToNameBinding<'a> {
@@ -1012,7 +1012,7 @@ pub struct Resolver<'a> {
     /// Table for mapping struct IDs into struct constructor IDs,
     /// it's not used during normal resolution, only for better error reporting.
     /// Also includes of list of each fields visibility
-    struct_constructors: DefIdMap<(Res, ty::Visibility, Vec<ty::Visibility>)>,
+    struct_constructors: DefIdMap<(Res, ty::Visibility<DefId>, Vec<ty::Visibility<DefId>>)>,
 
     /// Features enabled for this crate.
     active_features: FxHashSet<Symbol>,
@@ -1808,7 +1808,11 @@ impl<'a> Resolver<'a> {
         self.pat_span_map.insert(node, span);
     }
 
-    fn is_accessible_from(&self, vis: ty::Visibility, module: Module<'a>) -> bool {
+    fn is_accessible_from(
+        &self,
+        vis: ty::Visibility<impl Into<DefId>>,
+        module: Module<'a>,
+    ) -> bool {
         vis.is_accessible_from(module.nearest_parent_mod(), self)
     }
 
@@ -1862,10 +1866,8 @@ impl<'a> Resolver<'a> {
                     self.crate_loader.maybe_process_path_extern(ident.name)?
                 };
                 let crate_root = self.expect_module(crate_id.as_def_id());
-                Some(
-                    (crate_root, ty::Visibility::Public, DUMMY_SP, LocalExpnId::ROOT)
-                        .to_name_binding(self.arenas),
-                )
+                let vis = ty::Visibility::<LocalDefId>::Public;
+                Some((crate_root, vis, DUMMY_SP, LocalExpnId::ROOT).to_name_binding(self.arenas))
             }
         })
     }