internal: remove one usage of a slow method

Author: matklad

crates/hir/src/lib.rs

@@ -436,6 +436,7 @@ impl Module {
         module_data.visibility
     }
 
+    /// XXX: this O(N) rather O(1) method, avoid using it if you can.
     pub fn visibility_of(self, db: &dyn HirDatabase, def: &ModuleDef) -> Option<Visibility> {
         let def_map = self.id.def_map(db.upcast());
         let module_data = &def_map[self.id.local_id];
@@ -841,6 +842,13 @@ impl Variant {
     }
 }
 
+/// Variants inherit visibility from the parent enum.
+impl HasVisibility for Variant {
+    fn visibility(&self, db: &dyn HirDatabase) -> Visibility {
+        self.parent_enum(db).visibility(db)
+    }
+}
+
 /// A Data Type
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
 pub enum Adt {

crates/ide_assists/src/handlers/fix_visibility.rs

@@ -46,7 +46,17 @@ fn add_vis_to_referenced_module_def(acc: &mut Assists, ctx: &AssistContext) -> O
     let current_module = ctx.sema.scope(path.syntax()).module()?;
     let target_module = def.module(ctx.db())?;
 
-    let vis = target_module.visibility_of(ctx.db(), &def)?;
+    let vis = match def {
+        hir::ModuleDef::Module(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::Function(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::Adt(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::Variant(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::Const(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::Static(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::Trait(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::TypeAlias(it) => it.visibility(ctx.db()),
+        hir::ModuleDef::BuiltinType(_) => return None,
+    };
     if vis.is_visible_from(ctx.db(), current_module.into()) {
         return None;
     };

crates/ide_db/src/defs.rs

@@ -52,9 +52,7 @@ impl Definition {
                 ModuleDef::Static(it) => Some(it.visibility(db)),
                 ModuleDef::Trait(it) => Some(it.visibility(db)),
                 ModuleDef::TypeAlias(it) => Some(it.visibility(db)),
-                // NB: Variants don't have their own visibility, and just inherit
-                // one from the parent. Not sure if that's the right thing to do.
-                ModuleDef::Variant(it) => Some(it.parent_enum(db).visibility(db)),
+                ModuleDef::Variant(it) => Some(it.visibility(db)),
                 ModuleDef::BuiltinType(_) => None,
             },
             Definition::Macro(_)