From a3c2f5126fb9f2575584d12335b6e7e82deec45a Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sat, 20 Jun 2020 00:36:02 +0200
Subject: Recursively compute impl sets

---
 crates/ra_hir_ty/src/method_resolution.rs | 39 ++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/crates/ra_hir_ty/src/method_resolution.rs b/crates/ra_hir_ty/src/method_resolution.rs
index be685e12f..ed638c195 100644
--- a/crates/ra_hir_ty/src/method_resolution.rs
+++ b/crates/ra_hir_ty/src/method_resolution.rs
@@ -65,26 +65,20 @@ impl CrateImplDefs {
         db: &dyn HirDatabase,
         krate: CrateId,
     ) -> Arc<CrateImplDefs> {
-        // FIXME: This should take visibility and orphan rules into account to keep the result
-        // smaller.
         let _p = profile("impls_from_deps_query");
         let crate_graph = db.crate_graph();
         let mut res = CrateImplDefs {
             inherent_impls: FxHashMap::default(),
             impls_by_trait: FxHashMap::default(),
         };
-        let mut seen = FxHashSet::default();
-        let mut worklist =
-            crate_graph[krate].dependencies.iter().map(|dep| dep.crate_id).collect::<Vec<_>>();
-        while let Some(krate) = worklist.pop() {
-            if !seen.insert(krate) {
-                continue;
-            }
-
-            // No deduplication, since a) impls can't be reexported, b) we visit a crate only once
-            res.fill(db, krate);
 
-            worklist.extend(crate_graph[krate].dependencies.iter().map(|dep| dep.crate_id));
+        // For each dependency, calculate `impls_from_deps` recursively, then add its own
+        // `impls_in_crate`.
+        // As we might visit crates multiple times, `merge` has to deduplicate impls to avoid
+        // wasting memory.
+        for dep in &crate_graph[krate].dependencies {
+            res.merge(&db.impls_from_deps(dep.crate_id));
+            res.merge(&db.impls_in_crate(dep.crate_id));
         }
 
         Arc::new(res)
@@ -116,6 +110,25 @@ impl CrateImplDefs {
         }
     }
 
+    fn merge(&mut self, other: &Self) {
+        for (fp, impls) in &other.inherent_impls {
+            let vec = self.inherent_impls.entry(*fp).or_default();
+            vec.extend(impls);
+            vec.sort();
+            vec.dedup();
+        }
+
+        for (trait_, other_map) in &other.impls_by_trait {
+            let map = self.impls_by_trait.entry(*trait_).or_default();
+            for (fp, impls) in other_map {
+                let vec = map.entry(*fp).or_default();
+                vec.extend(impls);
+                vec.sort();
+                vec.dedup();
+            }
+        }
+    }
+
     pub fn lookup_impl_defs(&self, ty: &Ty) -> impl Iterator<Item = ImplId> + '_ {
         let fingerprint = TyFingerprint::for_impl(ty);
         fingerprint.and_then(|f| self.inherent_impls.get(&f)).into_iter().flatten().copied()
-- 
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