Simplify

crates/rust-analyzer/src/main_loop.rs

@@ -96,13 +96,11 @@ pub fn main_loop(ws_roots: Vec<PathBuf>, config: Config, connection: Connection)
     let mut world_state = {
         let workspaces = {
             // FIXME: support dynamic workspace loading.
-            let mut visited = FxHashSet::default();
-            let project_roots = ws_roots
+            let project_roots: FxHashSet<_> = ws_roots
                 .iter()
                 .filter_map(|it| ra_project_model::ProjectRoot::discover(it).ok())
                 .flatten()
-                .filter(|it| visited.insert(it.clone()))
-                .collect::<Vec<_>>();
+                .collect();
 
             if project_roots.is_empty() && config.notifications.cargo_toml_not_found {
                 show_message(