Add back optimizations

Author: LHolten

src/tools/rust-analyzer/crates/base-db/src/input.rs

@@ -499,13 +499,18 @@ impl CrateGraph {
     /// Extends this crate graph by adding a complete second crate
     /// graph and adjust the ids in the [`ProcMacroPaths`] accordingly.
     ///
+    /// This will deduplicate the crates of the graph where possible.
+    /// Note that for deduplication to fully work, `self`'s crate dependencies must be sorted by crate id.
+    /// If the crate dependencies were sorted, the resulting graph from this `extend` call will also
+    /// have the crate dependencies sorted.
+    ///
     /// Returns a map mapping `other`'s IDs to the new IDs in `self`.
     pub fn extend(
         &mut self,
         mut other: CrateGraph,
         proc_macros: &mut ProcMacroPaths,
     ) -> FxHashMap<CrateId, CrateId> {
-        self.sort_deps();
+        let m = self.len();
         let topo = other.crates_in_topological_order();
         let mut id_map: FxHashMap<CrateId, CrateId> = FxHashMap::default();
         for topo in topo {
@@ -514,9 +519,8 @@ impl CrateGraph {
             crate_data.dependencies.iter_mut().for_each(|dep| dep.crate_id = id_map[&dep.crate_id]);
             crate_data.dependencies.sort_by_key(|dep| dep.crate_id);
 
-            let find = self.arena.iter().find(|(_, v)| *v == crate_data);
-            let new_id =
-                if let Some((k, _)) = find { k } else { self.arena.alloc(crate_data.clone()) };
+            let find = self.arena.iter().take(m).find_map(|(k, v)| (v == crate_data).then_some(k));
+            let new_id = find.unwrap_or_else(|| self.arena.alloc(crate_data.clone()));
             id_map.insert(topo, new_id);
         }